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DIY Stompboxes => Building your own stompbox => Topic started by: frequencycentral on December 25, 2008, 04:12:06 PM

Title: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 25, 2008, 04:12:06 PM
I've been wanting to build a multimode (highpass/bandpass/lowpass) envelope filter for a while using a LM13700. This thing has been on my breadboard for the best part of 2 months, I finished the build last week and have been making some minor tweaks since. It's pretty close to what I wanted now. Maybe just a few more tiny tweaks. I can't claim to have designed it from scratch - it's actually based on the filter and envelope detector in this circuit (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf) but with a number of modifications. It's also fairly close to the Tonepad Maestro FSH but with the addition of the extra modes, but I didn't choose to include sample and hold. As usual - I don't claim to be a whizzbang EE, so this is fully open for hacking/modding/improving. I'll be posting some soundclips in the next few days - hey its a busy time of year! Rest assured, it sounds funky as hell!

(http://i210.photobucket.com/albums/bb292/frequencycentral/FunkyMFMultimodeFilter.jpg)

(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0003-5.jpg)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on December 25, 2008, 04:24:30 PM
Very nice!  Any thoughts to having a dry/filter blend pot?  That gain stage just ahead of the "range" control seems like an appropriate spot to tap the dry signal, and the op-amp output stage provides an opportunity to mix them together.

Just a thought.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 25, 2008, 06:15:33 PM
Thanks Mark. A blend control would probably be useful to some users, and would be easy enough to add as you suggest. I didn't really consider one because I was aiming for as 'synthy ' a sound as possible - to this end, I'm using a distortion before this pedal, the filtering is far more pronounced that way than with a clean guitar signal. That gain stage with the trimpot before the envelope detector was added to give the ability to boost a clean guitar signal enough to give a meaninful signal to the envelope detector. To be honest, I was also trying to keep the knob count down, it could have ended up having a frequency control too, and a depth control between the envelope and OTA control inputs.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: theehman on December 25, 2008, 06:28:15 PM
Very nice!  I may have to build one of these myself.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 25, 2008, 06:32:24 PM
Very nice!  I may have to build one of these myself.


Thanks theehman - I should also mention I run all my pedals, this one included, at 12 volts. I'll set my power supply to 9 volts and see how it works that way - should be fine though.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: flo on December 27, 2008, 06:47:01 AM
An idea when using an envelope filter on a guitar signal with a lot of distortion:
Make a separate input for the envelope detector and feed that with the clean guitar signal.
A heavy distorted signal usually has a lot of compression/sustain: A a very slow decay. The clean signal usually has a much faster decay.
This gives a nice "synthy" combination of filtering a signal with lots of harmonics using a snappy decaying envelope.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 27, 2008, 07:05:34 AM
That's a good idea flo. It did occur to me during the breadboarding phase to maybe add a built-in distortion to do what you describe, as with these type of devices what comes out is largely based on what comes before it in the pedal chain.

I also looked at the Stompboxology article (found on Moosapotamus's site) on envelope detectors. What particularly interested me was the leading edge detector, which would appear to be able to specify the decay irrespective of the input signal. Has anyone done this before?

To my ears, the standout sounds with my build are the autowah type slow attack sounds with a distortion before the filter. A bit of muting is needed to get those fast decay sounds with a distortion before the filter - but they do come more naturally with no distortion. I think that if a new pedal gives you just one great useable sound to add to your arsenal then it's a win.

Hmmm, live and learn! I just know I'm going to do another envelope filter (at some point in the future) implementing stuff I didn't use in this design - blend control, built-in distortion, maybe octaves too. It will probably end up having a lot more knobs than this one!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on December 28, 2008, 03:03:06 PM
I have a few LM13600s lying around.  Will these work for this build?  I'm still a bit new to the world of transconductance op amps.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 28, 2008, 03:46:40 PM
I have a few LM13600s lying around.  Will these work for this build?  I'm still a bit new to the world of transconductance op amps.

Those LM13600 will work just fine!
Title: Funky Muthafunkin Sounclips!!
Post by: frequencycentral on December 28, 2008, 04:00:07 PM
Here's a soundclip/montage featuring my trademark lousy playing style: http://www.aronnelson.com/DIYFiles/up/Funky_MF.mp3

Recorded straight into my soundcard, with my trusty Valvecaster between the guitar and the Funky MF.  :icon_mrgreen:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on December 28, 2008, 04:24:08 PM
That sounds deadly Rick!  I'm definitely going to have to try this.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on December 28, 2008, 09:22:35 PM
How does it sound on bass?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 29, 2008, 07:16:25 AM
How does it sound on bass?

Sounds cool with bass too - I'll get some bass soundclips together later today.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Ben N on December 29, 2008, 08:57:34 AM
That's a good idea flo. It did occur to me during the breadboarding phase to maybe add a built-in distortion to do what you describe, as with these type of devices what comes out is largely based on what comes before it in the pedal chain.
No need to actually build it in. All you would to modify for a sidechain is to wire a switching jack into the circuit right before the envelope detector so that if nothing is plugged in, you are still drawing the envelope signal off the input. It is also probably a good idea to have some kind of buffer/splitter at the front of the signal chain where you tap off the clean envelope signal.
This idea is useful for any kind of envelope-based effects, such as compressors, to let you put the effect in the signal chain where it is most useful, without worrying about added noise or a degraded signal envelope.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 29, 2008, 01:45:27 PM
How does it sound on bass?

Sounds cool with bass too - I'll get some bass soundclips together later today.

Here's some bass soundclips: http://www.aronnelson.com/DIYFiles/up/Funky_MF_Bass.mp3

My bass is a Washburn Bantam Active RB2500. I found I got the best results running it through my NanoCompressor and then into the Funky MF.

I think if I were planning to use this for bass I would definately add a blend control as Mark Hammer suggested - and always use a compressor before it in the chain.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on December 29, 2008, 03:26:06 PM
always use a compressor before it in the chain.

So it's not volume activated? I see that there's no LED, but does it just automatically run the range of the filter with any sound? Can you vary the length of the decay?

You also said that the sensitivity is set by a trimpot. Can you make that a regular pot? I've made some good sounds with my meatball, but I'm always tweaking the sensitivity based on what I'm playing. I know the filter is different in this. Would having a sensitivity knob be helpful?

Thanks
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Ben N on December 29, 2008, 03:31:49 PM
Unless it is set on an extreme setting, a compressor may well leave enough dynamics in the signal to trigger an envelope follower. However, this would be another benefit of a sidechain--send a nice, smooth, even, sustainy compressed signal through the filter, while your raw, uncompressed native electric guitar note drives the envelope detector in all its dynamic glory.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 29, 2008, 04:43:46 PM
always use a compressor before it in the chain.

So it's not volume activated? I see that there's no LED, but does it just automatically run the range of the filter with any sound? Can you vary the length of the decay?

You also said that the sensitivity is set by a trimpot. Can you make that a regular pot? I've made some good sounds with my meatball, but I'm always tweaking the sensitivity based on what I'm playing. I know the filter is different in this. Would having a sensitivity knob be helpful?

Thanks

Yes it is volume activated, I'm just finding that bass has too much dynamic range for the way I have the trimpot set I guess. I only really play bass when recording and I always comp it - maybe has more to do with my 'playing style'! Using the comp tames the bass a little for the envelope follower, without it going ove the top all the time. It's different with guitar.

The trimpot sets the range of the 'Range' control, if you get what I mean. think of the trimpot as coarse tuning, the 'Range' control as fine tuning. Set the trimpot up for the paticular application and then use the 'Range' control for tweaks. The trimpot and opamp form a x10 amplifier, turning the trimpot half its range make this a x5 amplifier etc.

EDIT:

I have to say that it's a lot easier to get good sounds out of the Funky MF with guitar than it is with bass. I did the design with guitar in mind, so it's set up for guitar really. Maybe someone should suggest some bass mods? I suspect it would involve changing the input cap and the cap before the envelope detector.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on December 30, 2008, 03:27:23 PM
There are a couple of things you can do.

One is to make the gain in that first op-amp stage greater for the mids and highs than for the lows, something like what is used in a more extreme fashion in the Rat.  So, stick a 3k9 fixed resistor and a .047uf cap in series and stick that in parallel with the 10k resistor from the inverting pin.  That way, adjustments of the trimpot will result in more gain for the content above 800hz or so, than for content below.

Alternatively, you have the 100k Range pot tied directly to the preceding op-amp's output.  You could stick a parallel RC combo between the op-amp and pot to allow for more attenuation of the signal for the low end than for the mids and highs.  So, a 22k resistor in parallel with a .0047uf-.01uf cap might get you a little more mid/treble drive (relative to bass) coming off the wiper of the Range pot at less-than-max settings.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on December 31, 2008, 03:48:57 AM
Not that this is any huge revelation, but I think most people, when modding for bass, use a 1uf to 10uf capacitor at input and output. Other than that, I'm not sure enough what the circuit does exactly to recommend anything. I would suggest that you make sure you don't lose the low frequencies anywhere, and it's important that the wah sound is present on an open E, or maybe even lower for some of those 5-stringers. It took me forever to tweak my meatball to make an actual wah sound on my open E. I don't know if that means the wah has to cover a range of frequencies that is just above the low E or not. What I mean is that it probably has to be proportional somehow, but I'm no engineer. I'm studying film  ;). I know that the high pass and bandpass filters on my meatball are only used when I'm showing friends what it can do. Lowpass is all that makes sense because the volume drop is so substantial. It's interesting to have the volume vary on the range of the note, but I think I'd rather have a volume controled volume filter for that (which I'm assuming amounts to a compressor in moderation?).

Well, that's all the rambling I have right now. I imagine you probably figured most of that out before I said anything. I don't know any of the math for this stuff, so someone else will have to help you out there.
Good luck. I'm excited to see what you come up with. Always looking for new filters.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 31, 2008, 07:47:35 AM
Some good ideas there for bass mods. However - I'm not planning to mod this for bass myself, I only play bass for recording demos, and usually keep it clean aside from a little compression. So if anyone wants to take the bass mod ideas and run with them - be my guest! I would agree re highpass and bandpass being difficult to use with bass though - so maybe for bass this design isnt worth the extra effort - no point making a multimode filter and only ever using lowpass!

On another tack:

I mentioned in my first post about a few tiny tweaks I'm considering. Having lived with the unit for a while, I'm planning to make the 10K resistor between the Release control and ground a little bigger. This resistor sets the minimum release time. As I have it now with the 10K resistor it's too short - there is a weird low frequency hum when Attack and Release are both at minimum, so I'll try going up in small increments (22K, 47K, 68K, 100K) until its perfect. Not really a major fix, and in practice at the moment I'm just keeping the Release control a few degrees off minimum.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on December 31, 2008, 10:12:33 AM
It bears noting that the original circuit from which the filter section was extracted was an electronic cymbal.  So clearly it was not conceived as something intended to handle low end.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on December 31, 2008, 08:36:37 PM
It bears noting that the original circuit from which the filter section was extracted was an electronic cymbal.  So clearly it was not conceived as something intended to handle low end.

That said, this filter sounds incredibly close to my Oberheim SEM filter (which is 3080 and multimode), my old EDP Wasp filter (again 3080 and multimode), so maybe bandpass and highpass are operating out of the frequency range of bass guitar. Put a low freq sawtooth through this filter and is sings! I think the main issue with this filter and bass guitar has to do with the setup of the envelope follower rather than the filter itself.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on January 03, 2009, 02:24:37 PM
I put the filter section of this pedal into my slackfilter the other day and I really like it.  Much less of a headache to get it to work right.  Once I get it tweaked to near perfect I'll be posting some sound samples and vero layouts (unless the winter monster of laziness gets to me).
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on January 05, 2009, 04:12:59 AM
It bears noting that the original circuit from which the filter section was extracted was an electronic cymbal.  So clearly it was not conceived as something intended to handle low end.
Which circuit is that? I thought this came from the FSH-1 a lot? Or did I read that somewhere else?

Anyway, I know the multimode part is not really for bass, but I wonder sometimes why. I guess it makes sense that the bass frequencies can't be heard as well, but maybe it also adds up to the steps between the modes being too drastic.

Maybe I ask for too much. Anyway, awesome project, and I'll keep checking back.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on January 05, 2009, 09:17:47 AM
It bears noting that the original circuit from which the filter section was extracted was an electronic cymbal.  So clearly it was not conceived as something intended to handle low end.
Which circuit is that? I thought this came from the FSH-1 a lot? Or did I read that somewhere else?

Anyway, I know the multimode part is not really for bass, but I wonder sometimes why. I guess it makes sense that the bass frequencies can't be heard as well, but maybe it also adds up to the steps between the modes being too drastic.

Maybe I ask for too much. Anyway, awesome project, and I'll keep checking back.
The very first post in this thread has the link, which you may have simply misread as an underlined phrase; "in this circuit" links you to http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf

Multimode/state-variable filters (which this is) are most definitely for bass.  That's one of the many reasons why the Mu-Tron remained so popular with bassists for so many years.  What is not recommended for bass are the bandpass and highpass settings on state-variable filters, since one loses so much of the "meat" of the bass tone.  That's why the Q-Tron has a "Mix" setting in addition to BP/LP/HP.  The Mix combines bandpass and clean signal so that you get the character of a bandpass without losing the oomph.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on January 05, 2009, 04:39:05 PM
That's why the Q-Tron has a "Mix" setting in addition to BP/LP/HP.  The Mix combines bandpass and clean signal so that you get the character of a bandpass without losing the oomph.
My meatball also has that. I might have to check it out that way. Would that provide the "resonance filter" sound? I've been trying to figure that out for a while, because I know they exist, but I have no idea what they are. My old digital multi-effects had one and I know the same sound come up a lot in Les Claypool's solo/non-primus stuff. I bought some crappy 9v adaptors, so I'll have to do some soldering before I can test again. The gauge is the smallest I've ever seen. There's like two strands in there.

Anyway, thanks for the clarification. I've been looking for something with a little more consistency in the filter section as the meatball has a tendency to do some banshee sounds with color turned up too high. The randomness can be cool, but I'd rather have the consistency. The LED-less designs are more consistent, I'm assuming, or am I totally wrong on that?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on January 05, 2009, 10:32:08 PM
I recorded a sample of my build that used this filter. 

http://www.aronnelson.com/DIYFiles/up/philter_hartman_demo.mp3

Excuse the slop playing and the little bit of hiss my sound card added to it.  First few samples are the pedal by itself, last few are with a Slacktave, Nyquist Aliaser and modded big muff respectively.   Like I stated earlier, mine has an LFO and an adjustable frequency pot since it's based on the slackfilter.  With the frequencies really low, the bias on the LM13600 gets sort of starved and things start sounding mucho weird.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on January 21, 2009, 02:20:51 AM
I hope you guys don't mind this, but I'd like to ask a few questions about how this thing works. From what I can tell, like in the meatball, this has one section that uses an opamp to convert volume into voltage. Then that voltage is put into one part of the lm13700. There seems to be two filter stages, which, I think I read somewhere, increases the "talky" sound of the wah. Where does the parametric filter come from? I will admit I have no idea how the lm13700 works, so maybe there's something there that I'm missing. Any explanation would be awesome.  Thanks.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on January 21, 2009, 09:10:33 AM
Read up on state-variable filters.  This is simply another form of one.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 21, 2009, 12:52:13 PM
I hope you guys don't mind this, but I'd like to ask a few questions about how this thing works. From what I can tell, like in the meatball, this has one section that uses an opamp to convert volume into voltage. Then that voltage is put into one part of the lm13700. There seems to be two filter stages, which, I think I read somewhere, increases the "talky" sound of the wah. Where does the parametric filter come from? I will admit I have no idea how the lm13700 works, so maybe there's something there that I'm missing. Any explanation would be awesome.  Thanks.

Worth reading: "The Technology of Auto-Wahs / Envelope-Controlled Filters" at http://www.geofex.com/

.....and http://en.wikipedia.org/wiki/Voltage-controlled_filter

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on January 21, 2009, 07:48:46 PM
Is a layout for this in the works?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 22, 2009, 01:32:45 PM
Is a layout for this in the works?

I built the prototype on perf - so I've no plans to do a layout sorry. Why not try one yourself using 'DIY Layout Creator' software - and then post it here!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on January 22, 2009, 03:50:56 PM
I'll give a shot...
edit: which opamps are which?  would the 324 be all the sections on the top and left of the schem and the 62 be on the right?  If you can't tell, I'm pretty new to layouts - I've only done a few very simple circuits...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on January 22, 2009, 04:46:07 PM
Definitely beyond my ability - sorry....
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 22, 2009, 04:48:38 PM
I'll give a shot...
edit: which opamps are which?  would the 324 be all the sections on the top and left of the schem and the 62 be on the right?  If you can't tell, I'm pretty new to layouts - I've only done a few very simple circuits...

It really doesnt matter which opamps are which. I just used the 324 and the 062 because thats what I had available. You could use any opamps really - 3 duals if you wanted. I'm particularly fond of the 324 as a quad because the pinout is so easy to remember.

There is a fair amount of off-board wiring in this build - more than double the average fuzz or distortion. I'm not trying to put you off, but being swamped by too much off-board could be very frustrating - and tough to debug. Good luck, and help is always available here should you choose to go ahead.

Rick
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 22, 2009, 04:49:38 PM
Definitely beyond my ability - sorry....

 :'(
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on January 22, 2009, 05:54:18 PM
Here, this isn't a full layout for the Funky MF, but this is the layout of the board of the filter seciton that I used for my build.  Ignore the unused rows.

(http://img.photobucket.com/albums/v484/boogdish/MFfilterboard.gif)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on January 23, 2009, 10:13:48 PM
I thought I would take up the challenge of creating a layout for this effect.  Would someone kindly double check this?  I am not sure I am going to build it, but thought since people were asking for a layout that I would create one.

Here it is:
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38445

If there are any corrections or errors please let me know.

Cheers,

Steve
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on January 24, 2009, 05:26:55 AM
I hope you guys don't mind this, but I'd like to ask a few questions about how this thing works. From what I can tell, like in the meatball, this has one section that uses an opamp to convert volume into voltage. Then that voltage is put into one part of the lm13700. There seems to be two filter stages, which, I think I read somewhere, increases the "talky" sound of the wah. Where does the parametric filter come from? I will admit I have no idea how the lm13700 works, so maybe there's something there that I'm missing. Any explanation would be awesome.  Thanks.

Worth reading: "The Technology of Auto-Wahs / Envelope-Controlled Filters" at http://www.geofex.com/

.....and http://en.wikipedia.org/wiki/Voltage-controlled_filter


I think I've read both of those, so let me be a little more specific. How does this filter work without using LEDs? The one in the GEOFEX article uses LEDs and the Meatball that I built uses LEDs. The FSH-1 and this project don't, and I've been curious about the difference. Also, is this one more controlled in sound? I know the meatball, with certain settings, can have some strange sounds. Then again, that probably depends on the detector, not the filter. Anyway, thanks again, and I'll take another look at those articles.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: flo on January 24, 2009, 06:13:05 AM
I works by using an OTA which is a voltage controlled current source.
Operational Transconductance Amplifier:
http://en.wikipedia.org/wiki/Operational_transconductance_amplifier

Just like with a LED/LDR combo or other means, the OTA provides a way to change the cutoff frequency of the filter usually wiring it as a voltage controlled resistor.

Check also the datasheet of the LM13700 OTA chip.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 24, 2009, 06:25:35 AM
I thought I would take up the challenge of creating a layout for this effect.  Would someone kindly double check this?  I am not sure I am going to build it, but thought since people were asking for a layout that I would create one.

Here it is:
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38445

If there are any corrections or errors please let me know.

Cheers,

Steve

That's a very impressive piece of work Steve - I couldn't do what you've done there.

Thanks and respect. I'll check it over in detail over the weekend.

I hope you guys don't mind this, but I'd like to ask a few questions about how this thing works. From what I can tell, like in the meatball, this has one section that uses an opamp to convert volume into voltage. Then that voltage is put into one part of the lm13700. There seems to be two filter stages, which, I think I read somewhere, increases the "talky" sound of the wah. Where does the parametric filter come from? I will admit I have no idea how the lm13700 works, so maybe there's something there that I'm missing. Any explanation would be awesome.  Thanks.

Worth reading: "The Technology of Auto-Wahs / Envelope-Controlled Filters" at http://www.geofex.com/

.....and http://en.wikipedia.org/wiki/Voltage-controlled_filter


I think I've read both of those, so let me be a little more specific. How does this filter work without using LEDs? The one in the GEOFEX article uses LEDs and the Meatball that I built uses LEDs. The FSH-1 and this project don't, and I've been curious about the difference. Also, is this one more controlled in sound? I know the meatball, with certain settings, can have some strange sounds. Then again, that probably depends on the detector, not the filter. Anyway, thanks again, and I'll take another look at those articles.

Aah, ok! The LM13700 belongs to a family of chips known as OTAs, or Operational Transconductance Amplifiers (along with LM13600, CA3080, CA3094, and some others): http://en.wikipedia.org/wiki/Operational_transconductance_amplifier

So - imagine an opamp with the Meatball's LED/LDR combination built in to it. That's not actually how it works, but probably the easiest way to think about it. Or imagine a compressor with a side chain.

The OTA's Iabc (pins 1 and 16 on the 13700, as it is a dual OTA) input accepts a current which defines the output. So where other circuits use a LED/LDR or a FET as a voltage controlled resistor, an OTA circuit uses a voltage applied via a resistor to the Iabc input to do the same job. Probably not the most technical explanation, but that's how I rationalise it - Mark Hammer will no doubt be along shortly with a more detailed/informed explanation!

Your second question - 'is this one more in controlled in sound?' - you're probably right in saying that it depends on the detector part of the circuit. OTAs are used a lot in synth VCFs/VCAs, and can be very controlled, as there is no detector in those circuits.



EDIT: thanks flo - we were typing at the same time. I posted anyway.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on January 24, 2009, 09:46:15 AM
UPDATE:

I have moved the pads around in the top left corner of the board so that they are all in a single line now.  This doesn't change any other part of the board, so the layout really hasn't changed at all, just the lining up of those pads.  I have uploaded the new file here and deleted the other one from my gallery.

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38490

Cheers and thanks for the compliment Rick.  I just hope I haven't committed any major routing errors or unconventional routing practices.

Steve
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 24, 2009, 09:56:00 AM
UPDATE:

I have moved the pads around in the top left corner of the board so that they are all in a single line now.  This doesn't change any other part of the board, so the layout really hasn't changed at all, just the lining up of those pads.  I have uploaded the new file here and deleted the other one from my gallery.

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38490

Cheers and thanks for the compliment Rick.  I just hope I haven't committed any major routing errors or unconventional routing practices.

Steve

I've spotted one thing to be aware of:
 
LM324 - pin 4 +ve, pin 11 ground.
LM13700 - pin 6 ground, pin 11 +ve.

.....so it needs bearing in mind that LM324 pin 1 should be connected to the 1n4148. In prctice, this doesnt change anything else, as the LM324 pinouts are so symetrical. Worth indicating which is pin 1 on each chip though.

I'll do some more checking.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on January 24, 2009, 10:21:53 AM
Pin 1 on each IC is noted by the square pad.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on January 24, 2009, 10:24:38 AM
Fantastic layout - I'm always amazed how you guys come up with these layouts.  Thank you, thank you, thank you!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 24, 2009, 10:29:17 AM
Pin 1 on each IC is noted by the square pad.

Oh yeah - nice! Didn't spot that!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Radamus on January 24, 2009, 02:41:31 PM
Thanks for clarifying. I figured it had something to do with that. I'll take a look at the OTA wikipedia page. Does this use less current than an LED/LDR combo It would seem like it would as LEDs can use a lot. Is there any differences with using simply a voltage controlled OTA rather than the LDR? I thought the behavior of the LDR allowed the sound to be so rounded, as in it takes a little while for the resistance to fall back down again, even thought the LED is off.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on January 24, 2009, 03:31:39 PM
I really should modify my IC graphic that I use though to add the pin one marker or the little scooped u shap at the top end of the IC.  When I am back in town I will adjust and update the file.

I haven't had the chance to print this out and trace over it to check yet either.  I usually print the schematic and the layout and go to town with the highlighter.  Although that is also the same thing I do when designing the layout.  I open the scemo up in photoshop and higlight the connections and parts as I connect them.

The layout was done using Inkscape and a home made library of parts.  It works for me until I learn Eagle or I get too frustrated with it.

Cheers,

Steve
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 01, 2009, 11:54:05 AM
Anyone built this from my layout yet?  I haven't had time yet, but thought someone might have...  I have been busy with a Dub Machine and a Boss Slow Gear.  Fun stuff.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Slade on February 01, 2009, 01:10:44 PM
Thanks for this wonderful project, Rick, and thanks for your beautiful layout, Mr. Little.
I've just bought some LM13700 (LM13600 is really difficult to find at my country) and I'll give a try to your layout soon.

Greetings!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 01, 2009, 05:35:25 PM
I just finished assembling and populating and no funk.  It passes signal but it's just plain uneffected signal - the overall volume is also  decreased.  It also sucked a 9v that I was using just for testing before boxing up.  I had it plugged in for maybe ten minutes and it went down to 8.3v from 10v.  I'll post voltages after the Super Bowl....  I know they are screwy.

edit: I used a lm13600d - would this make a difference?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 01, 2009, 06:18:23 PM
I just finished assembling and populating and no funk.  It passes signal but it's just plain uneffected signal - the overall volume is also  decreased.  It also sucked a 9v that I was using just for testing before boxing up.  I had it plugged in for maybe ten minutes and it went down to 8.3v from 10v.  I'll post voltages after the Super Bowl....  I know they are screwy.

edit: I used a lm13600d - would this make a difference?

OK, post your voltages, I'll take mine and post them too. Did you use orangetones' layout? I'll check that too. Is the LM324 in the right way around? It would be worth fiddling with the trimmer, and the Range pot, as at some settings the filter could be alway open, and would sound clean. Also, triple check all you off-board wiring - there's a lot of it right? I haven't tried mine with a battery, I run mine from a 12 volt PS. I'm concerned that you have volume loss, as the volume control provides quite a bit of boost from unity if turned fully clockwise. Not sure about the 13600d - I'll look it up - but it should be the same.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 01, 2009, 08:33:07 PM
OK, I tacked a power jack and powered from an adaptor...

Here we go:

V=8.83v

LM324
1 7.58
2 0.20
3 0.20
4 8.83
5 6.52
6 6.85
7 6.85
8 4.43
9 4.42
10 4.37
11 0.00
12 4.37
13 4.41
14 4.41

LM13600d

1 1.31
2 0.00
3 4.41
4 4.41
5 0.76
6 0.00
7 0.76
8 0.00
9 0.00
10 0.76
11 8.83
12 0.76
13 4.41
14 4.41
15 0.00
16 1.31

TL072
1 4.41
2 4.41
3 4.20
4 0.00
5 4.41
6 8.05
7 8.05
8 8.83

I haven't checked in comparison to the schematic yet - I'm doing that during the 3rd quarter.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 02, 2009, 09:50:49 AM
I've been over all the external voltage connections and they seem alright.  I'm not sure about the internal connections of the IC's and what they should be so I'll need some help there.  I also went over the layout and schematic with a highlighter and everything seems to be in the right place.  The effect does seem to change the frequency response of the signal - it cuts high frequencies.  One thing I did as a temporary measure because I did not have a SP3T switch is to use 3 SPST switches with the common pole daisy-chained and each mode independently switchable.  There is no difference when switches are thrown other than no signal is passed when they are all off.  I plan on ordering a SP3T switch soon...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 02, 2009, 02:53:13 PM
OK, here's my voltages. I measured them with all the pots (including the trimmer) at halfway - 12 o'clock. The mode was set to HP. Nothing plugged into the input or output. My PS reads 11.99 volts. I've had to retrace my steps a little, as my build is on perf, and the opamps are in different places to the orangetones' PCB - not that it matters. I'm pretty sure I got it right. Also, just to be sure, I just tested it at 9 volts and it runs just the same as at the 12 volts I usually run it at. As I took my measurements at 12v and yours are at 9v, you'll have to factor mine down by 25% - sorry that's a hassle. I suggest you set all the pots (including the trimmer) at halfway - 12 o'clock , and take your readings again, as how the knobs are set will affect the voltages. Then you'll be comparing like with like. Post them again and we'll analyse them.

LM13700

1 - 1.025
2 - 0.002
3 - 5.98
4 - 5.98
5 - 7.13
6 - 0.00
7 - 7.13
8 - 5.93
9 - 6.01
10 - 7.19
11 - 11.99
12 - 7.19
13 - 5.99
14 - 5.99
15 - 5.99
16 - 1.025

TL062

1 - 5.99
2 - 5.99
3 - 5.97
4 - 0.00
5 - 5.78
6 - 5.96
7 - 5.95
8 - 11.99

LM324

1 - 0.001
2 - 0.009
3 - 0.003
4 - 11.99
5 - 0.197
6 - 0.655
7 - 0.655
8 - 5.96
9 - 6.00
10 - 5.99
11 - 0.00
12 - 5.99
13 - 6.00
14 - 5.99
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 02, 2009, 06:07:02 PM
I switched to a 12v adapter.  Here are the voltages in comparison:

V=12.14v


LM13700

1 - 1.025        1.33
2 - 0.002        0.02
3 - 5.98          6.07
4 - 5.98          6.07
5 - 7.13          0.77   *
6 - 0.00          0.00
7 - 7.13          0.77   *
8 - 5.93          0.00   *
9 - 6.01          0.00   *
10 - 7.19        0.80   *
11 - 11.99      12.14
12 - 7.19        0.80   *
13 - 5.99        6.07
14 - 5.99        6.07
15 - 5.99        0.69   *
16 - 1.025      1.32

TL062

1 - 5.99         6.07
2 - 5.99         6.07
3 - 5.97         5.78
4 - 0.00         0.00
5 - 5.78         6.01
6 - 5.96         6.07
7 - 5.95         6.07
8 - 11.99       12.14

LM324

1 - 0.001        10.95   *
2 - 0.009        0.30
3 - 0.003        0.30
4 - 11.99        12.14
5 - 0.197        9.42     *
6 - 0.655        9.73     *
7 - 0.655        9.73     *
8 - 5.96          6.07
9 - 6.00          6.07
10 - 5.99        6.01
11 - 0.00        0.00
12 - 5.99        6.01
13 - 6.00        6.08
14 - 5.99        6.10

I'll check the board for bridges across traces.  I don't really know what to make of the differences.
I have a question about the orientation of the diode - is it band side out to the 2M2 and Attack pot or the other way around.  I have it band side out to the 2M2.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 02, 2009, 06:35:51 PM
I have a question about the orientation of the diode - is it band side out to the 2M2 and Attack pot or the other way around.  I have it band side out to the 2M2.

Yup your diode is correct. It's late here - but I have a day off tomorrow (snow day - yay!!) so I'll give it some thought and see if I can work out why. Are you sure the PCB itself has no errors?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 02, 2009, 06:53:58 PM
Pin one of the LM324 seems oddly high.  Bad diode? Solder bridge?  The other areas of concern I haven't considered yet. That one just jumped out at me.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 02, 2009, 07:05:26 PM
Yeah, that's what I thought - replaced the diode, tried a different 324 and also a TL074 - no dice.  Reflowed all the solder pads, scraped in between all the close together pads - still.  I don't get it?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 02, 2009, 07:09:01 PM
Judging by your voltage readings you have the ICs in correctly.  Pin one is in the square hole for each IC correct?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 02, 2009, 07:48:39 PM
Yes, the IC's are all in correctly.  I did find a solder bridge.  Here are the new voltages compared to frequency centrals:

V=12.08v (the voltage went down a few 100ths - ?)

LM13700

1 - 1.025        0.91
2 - 0.002        .017
3 - 5.98          6.03
4 - 5.98          6.03
5 - 7.13          0.11   *
6 - 0.00          0.00
7 - 7.13          0.11   *
8 - 5.93          0.00   *
9 - 6.01          0.00   *
10 - 7.19        0.11   *
11 - 11.99      12.08
12 - 7.19        0.11   *
13 - 5.99        6.03
14 - 5.99        6.03
15 - 5.99        .025   *
16 - 1.025      0.89   *

TL062

1 - 5.99         6.04
2 - 5.99         6.04
3 - 5.97         5.75
4 - 0.00         0.00
5 - 5.78         5.98
6 - 5.96         6.04
7 - 5.95         6.04
8 - 11.99       12.08

LM324

1 - 0.001        0.25   
2 - 0.009        0.04
3 - 0.003        .005
4 - 11.99        12.08
5 - 0.197        0.12     
6 - 0.655        0.52     
7 - 0.655        0.52     
8 - 5.96          6.04
9 - 6.00          6.04
10 - 5.99        5.98
11 - 0.00        0.00
12 - 5.99        5.98
13 - 6.00        6.04
14 - 5.99        6.06

So the LM324 and TL062 seem in order.  The LM13600 is still not correct.  I'll keep looking...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 02, 2009, 07:57:46 PM
Have you read over the datasheets for the LM13700 versus the LM13600?

Found this:
http://dropmix.xs4all.nl/pipermail/synth-diy/2008-August/008908.html
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 02, 2009, 08:12:10 PM
Interesting...  I think I'm going to put this one aside for the time being.  The way I have the modes switched by SPST switches independently is having a negative effect.  I will be ordering the correct SP3T switch and I'll also get some LM13700's.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 03, 2009, 04:25:58 AM
Interesting...  I think I'm going to put this one aside for the time being.  The way I have the modes switched by SPST switches independently is having a negative effect.  I will be ordering the correct SP3T switch and I'll also get some LM13700's.

Seems like you've made some progress - well done! The 324 and 062 do look good now. Maybe you have another solder bridge? It would certainly help having the right switch for less confusion. Boogdish used a 13600 in his build - and the circuit I based (stole?) my design on (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf) used a 13600 too. So, I think the 13600d should work. I'll do some checking today, after I've finished the snowman!


EDIT: If you order a 2P3T switch you can hook up LEDs to the other pole to give a visual intication of which mode you are in. Unnessecary but cool.

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Boogdish on February 03, 2009, 08:07:00 PM
Capntasty, like Rick said, mine uses a LM13600D just as yours does.  I also used  SPST switches for selecting modes.

Have you tried measuring the voltage coming out of the envelope follower as you play?  I'd make sure that it's putting out a good amount of voltage first so you can isolate your problem.  If you don't have the extra hands to play the guitar or clips for your test leads to do a normal voltage check of this, you can try running the output of the buffer on the envelope follower into an LED, if the LED lights up when you play, you're putting out enough voltage.

Is your resonance knob affecting the sound at all?

This might be a bugger to debug, since Rick, you and I all used different layouts and I used different control voltages.

Also, Rick, I was being light-hearted when I said you stole the design, I hope that came across okay on the internet.  To quote The Simpsons "Everything's stolen now adays, why the fax machines just a waffle iron with a phone attached to it."
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 04, 2009, 10:09:28 AM
I'll take another whack at it... where are the test points for measuring voltage on the envelope follower?

edit: has anybody else used orangetones layout?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 04, 2009, 12:44:54 PM
.....you can try running the output of the buffer on the envelope follower into an LED, if the LED lights up when you play, you're putting out enough voltage.

That's a really good idea, and what I did when I was breadboarding the circuit. Has a look at  the circuit I based (stole?) my design on  (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf) - that has a LED attached, you could connect it like that. It would confirm that the follower part of the circuit is working.

Also, Rick, I was being light-hearted when I said you stole the design, I hope that came across okay on the internet.  To quote The Simpsons "Everything's stolen now adays, why the fax machines just a waffle iron with a phone attached to it."

Yup - no problemo - I have no qualms about 'borrowing' or tipping my hat to influences. The filter is also very similar to the state variable filter on the LM13700 data sheet. I like the Simpsons quote!

I'll take another whack at it... where are the test points for measuring voltage on the envelope follower?

You should hook up a DMM pin 1/16 of the 13600, that should change with the transient of any note you play. It should settle to a constant voltage with no note played.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: captntasty on February 06, 2009, 10:24:05 AM
So there is no voltage change when a signal is applied on pins 1/16...  what does this tell me?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 06, 2009, 11:03:20 AM
So there is no voltage change when a signal is applied on pins 1/16...  what does this tell me?

The issue must be with the envelope follower, either the signal not reaching it or not getting through it. Check the connections and component values around the three opamps that make up the follower.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on February 06, 2009, 01:21:50 PM
A naive question: If the LM13600 is governed by the current applied to pins 1/16, then are you supposed to see envelope-associated voltage changes? ???
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 06, 2009, 01:33:09 PM
A naive question: If the LM13600 is governed by the current applied to pins 1/16, then are you supposed to see envelope-associated voltage changes? ???

Equally naive answer: Uh I had assumed so but obviously not now you mention, as the 10K resistor changes the voltage output of the follower into a current.........so maybe it would be better to measure the voltage the other side of that resistor. I just checked now, and that obviously does change from almost nothing to heavily +ve when a note is played. Thanks Mark.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: puretube on February 06, 2009, 01:39:46 PM
A naive question: If the LM13600 is governed by the current applied to pins 1/16, then are you supposed to see envelope-associated voltage changes? ???

As much as the voltage across 2 seriesdiodes(-drops) changes with current-changes... (= ~ a few millivolts around the ~1.4V mark...)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 06, 2009, 02:03:30 PM
A naive question: If the LM13600 is governed by the current applied to pins 1/16, then are you supposed to see envelope-associated voltage changes? ???

Yes. I haven't looked at the schematic of this pedal to see if it's single or dual rail power but essentially, you can monitor the voltage at the Iabc pin to determine where your gain is. When working with these OTA's, you can easily figure out the current feeding the pin by looking at the voltage on the pin and dividing by the resistance. Full off (or in this case, the lowest filter cutoff) is heard when the voltage seen at the Iabc pin is equal to the voltage that is being applied to it, and full on is when you are feeding the device the max amount of current you designed your OTA circuit for (and the accompanying voltage that is "converted" through the current limiting resistor). It's the same as designing with a differential amplifier, you just have to limit the amount of current that your connected emitters see and from there, it's easy to determine things like gain, dynamic range, etc..
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on February 15, 2009, 10:23:07 PM
Will a CA3280 work in this?? I have a lot fo those, but no lm13600/13700's. :)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 16, 2009, 07:06:38 AM
Will a CA3280 work in this?? I have a lot fo those, but no lm13600/13700's. :)

Hmm - I'm not sure. I have no experience with working with that device. A quick look at the data sheet (http://www.datasheetcatalog.org/datasheet/intersil/fn1174.pdf) suggests that it should be functionally similar to 13600/13700 - but the pinout is very different. I also had trouble identifying where the buffers are. My guess is that it should work as a replacement with maybe some tweaking needed. The CA3280 has been discussed over at electro-music.com (http://electro-music.com/forum/index.php?f=112), and is featured in a few designs over there. Pesonally, I would breadboard it first. It is apparently superior to the 13600/13700.

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 21, 2009, 09:30:12 PM
I finally breadboarded this up.  Have some issues though.  Maybe someone here can point me in the right direction.  I get a very loud popping when the filter engages.  Loud pop/click as the sound comes in, then it sounds fine.   But this is of course not fine as everytime you pick a note, you get this loud popping surge!  Anything I should be looking for that might contribute to this?

I am using a 13700N, LM324 and NE5532(for the Vref and Output Buffer).  All stock values for everything else except 50k for the 47k pot and 500k for the 470k pot.  I am using some log pots, but that shouldn't really change anything sound wise, just control wise.

Thoughts on this?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 21, 2009, 09:54:57 PM
I finally breadboarded this up.  Have some issues though.  Maybe someone here can point me in the right direction.  I get a very loud popping when the filter engages.  Loud pop/click as the sound comes in, then it sounds fine.   But this is of course not fine as everytime you pick a note, you get this loud popping surge!  Anything I should be looking for that might contribute to this?

I am using a 13700N, LM324 and NE5532(for the Vref and Output Buffer).  All stock values for everything else except 50k for the 47k pot and 500k for the 470k pot.  I am using some log pots, but that shouldn't really change anything sound wise, just control wise.

Thoughts on this?

Your problem is that the signal is rising too fast. To your LM13700 has a really fast slew rate (50 V/us) and a quick dynamic like a guitar pluck (where the attack is perceivably instant) will look like an impulse function (the delta dirac function for you differential equations fans). This function is centered around 0 (0 V DC in our case), is infinitely thin (no frequency content) but is infinitely tall (LOUD!). In the case of your OTA circuit, this impulse function is a quick changing DC signal that is at the amplitude set by your envelope follower circuit. What do you get when you run a DC impulse into an audio circuit (or a speaker)...? A loud "THUMP!". The same effect happens when you touch a battery to a speaker really fast, you hear a real life example of the impulse function. To alleviate this, you need some sort of slew limiting circuit. This can be done a few different ways but to be honest, I've never designed or used one.

Deriving the definition of slew rate is easy and may lend towards some circuit ideas, however. Since slew rate is I/C, first derive the units of current and capacitance. Current is defined as the rate of charge per second (Q/t) and capacitance is the cap charge divided by the voltage across the cap (Q/V). Dividing these gives us our units, volts per second (usually given in V/us). So what you need is a circuit that limits the amount of current a capacitor sees.. I would think that a voltage to current converter feeding an integrator will you do what you need.. I'll see if I can come up with a circuit tonight (I'm obviously bored :D).
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 21, 2009, 10:56:11 PM
Hey, Thanks for the reply Cliff. 

When you said "to my lm13700" are you referring to the 13700N? or the lm13700 in general?

Why would this work for Rick, but not me?  Presumably he used the same chip.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 21, 2009, 11:24:34 PM
Every LM13700. I assume that the averaging capacitor in your envelope detector is too small. Making it larger (the cap going to ground after the diode) and will make it so that the envelope signal can't change as fast. I need a schematic to go any further, but I know your problem because it's a more general problem with audio stuff.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 21, 2009, 11:38:12 PM
Cliff,

Schematic is the one on the first page of this thread.  I'll try what you have mentioned though...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 22, 2009, 12:02:14 AM
That 10K resistor to ground from the release pot limits the release time - any shorter and weird stuff starts to happen. You could try making it a bigger value, or try dialling in a longer release. You shouldn't have to increase the value of the cap to ground that follows it.

I get a very loud popping when the filter engages.  Loud pop/click as the sound comes in, then it sounds fine.

Hmm, don't know why that should be. Is the effect acting as you would imagine it should other than this?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 12:21:43 AM
It is not the release that is the issue (I am assuming that by release here we are talking about the decay).

I haven't had much chance to play around with it yet, but it seems to be doing its thing.  I couldn't really experiment becuase the loud surging at the beginning of every note was too loud and the wife was getting a little mad!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 22, 2009, 12:37:19 AM
........and the wife was getting a little mad!

 :icon_mrgreen:

There are a full set of voltages I posted a couple of pages back. You could check yours against them. Also, have a fiddle with the trimpot.

I only ever use this pedal with a distortion before it - you could try that and see what you get. It will kind of compress the signal, simplify the waveform, and make it more useable for the envelope follower to handle.

Good luck!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 10:18:55 AM
Question (surprised it wasn't asked before), but do the voltages for the pin in your voltage posting match with the layout that I created?  i.e. are pins 1-3 that voltage divider on your tl062 voltages?, Are pins 1-3 on your LM324 the ones that connect to the diode and such?

I only ask because you probably didn't use the same parts of your opamp ICs for the same particular opamps in the circuit.  Right?

So again, do your pin readings match the pins on my posted layout?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 11:54:09 AM
Here are the voltages that I have nebbed using a 12V regulator.  I will go over the circuit later on and see if I have built it wrongly on the breadboard.  There is always the possibility tha tI have made an incorrect connection in laying it out.

I have probably made a mistake, but Rick, is there any chance that there is an error in the schematic?  Seeing as that other fellow had trouble with my board layout that follows the schematic properly?

I am hoping to get this to work...  We'll see!

LM324
1   0.253
2   0.014
3   0.004
4   12.19
5   0.025
6   0.055
7   0.055
8   9.99
9   5.96
10   5.95
11   0.001
12   5.95
13   5.97
14   0.014

LM13700
1   0.522
2   0.331
3   6.08
4   6.25
5   0.15
6   0.001
7   0.14
8   2.061
9   1.923
10   0.002
11   12.19
12   0.002
13   5.91
14   6.08
15   0.004
16   0.522

NE5532
1   6.08
2   6.08
3   6.05
4   0.002
5   2.061
6   2.753
7   1.356
8   12.19
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 01:28:03 PM
Just another thought, I am using some Log taper pots, so mid point on them woudl be different from mid point on yours (assuming you used all linear as stated in the schematic.)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 22, 2009, 02:53:00 PM
Question (surprised it wasn't asked before), but do the voltages for the pin in your voltage posting match with the layout that I created?  i.e. are pins 1-3 that voltage divider on your tl062 voltages?, Are pins 1-3 on your LM324 the ones that connect to the diode and such?

I only ask because you probably didn't use the same parts of your opamp ICs for the same particular opamps in the circuit.  Right?

So again, do your pin readings match the pins on my posted layout?

I based my voltages on your layout - which required some detective work!

I built my pedal directly from the schematic itself, so any mistakes there would have translated to my build too.

As for you using log pots - you could dial them in so the resistance is equal both sides of the wiper.

Just looking at all those voltages, it's one hell of a debug. You also might like to refer to the original schematic that I base my design on: this circuit (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf).
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 03:39:54 PM
Rick.  I agree, one heel of a debig.  I am going to trace the schematic again and go over the breadboard.  I might have something not connected properly.  I just got back from crosscountry skiing, so time for a shower and then a little circuitry!

I'll let you know if anything turns up...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 05:13:00 PM
Updated Voltages.  I had one pot switched with another.  (1M where 100k should be and viceversa).  I set all the pots for equal resistance on either side and then measured the voltage again.  Still the same problem (loud popping when filter engages). and still different voltages.

Next step is to check the chips.  See if there is something wrong with them.  Try different ones from my stock.  Check some values too. 

If anyone has any thoughts on specific areas of this circuit to check over, let me know!

The filter sounds great when it engages, but that darn pop!  Just like a loud static discharge!

LM324
1   0.064
2   0.010
3   0.004
4   12.19
5   0.037
6   0.055
7   0.055
8   9.68
9   5.77
10   5.76
11   0
12   5.77
13   5.77
14   4.18

LM13700N
1   0.522
2   0.01
3   6.08
4   6.24
5   0
6   0
7   0
8   2.254
9   1.863
10   0.002
11   12.19
12   0.003
13   5.92
14   6.09
15   0.1
16   0.522

NE5532
1   6.09
2   6.09
3   6.06
4   0
5   2.254
6   2.949
7   1.353
8   12.19
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 22, 2009, 06:02:32 PM
If anyone has any thoughts on specific areas of this circuit to check over, let me know!

The filter sounds great when it engages, but that darn pop!  Just like a loud static discharge!

The 10K resistor between the unity gain buffer and pins 1/16 of the 13700 is a critical value. The three resistors in that ara set the initial frequency of the filter. If that 10K is any lower you will have problems. Raise it and you will raise the initial frequency of the filter. You might try increasing the value a little - try 15K maybe. Also, play with the trimmer, mine is set halfway around at teh moment.

A little earlier in this thread Mark Hammer suggested a cap in series just before the range control - that might be a good idea, and maybe something I should experiment with on mine.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 06:49:18 PM
Rick,

I have checked everything,  even changed out the chips.  Checked the values, tried that 10k/15 thing.

Here is what I can see as the problem.  This damn popping!  It is like there is a gate or a threshold which I must pass before the filter takes effect, but once I have broken through, so to speak, I can play softly and get the funky sounds, as long as I don't let the envelope close fully (or else I have ot pick hard to get back into that envelope).

You see?

Does this make any sense?  Any thoughts on this? 

I kind of wondered if you driving this with a distortion or something avoided this problem.  How does yours sound when driving it clean?  Then again, you would probably notice the pop!

Maybe I will PM Mark Hammer for his thoughts incase he isn't reading this thread.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 22, 2009, 07:28:20 PM
Here is what I can see as the problem.  This damn popping!  It is like there is a gate or a threshold which I must pass before the filter takes effect, but once I have broken through, so to speak, I can play softly and get the funky sounds, as long as I don't let the envelope close fully (or else I have ot pick hard to get back into that envelope).

I get it. Mine doesn't do that. If you're getting 'funk' then the filter is working well. It would seem to be a problem with the envelope follower. Did you try it with a distortion before it yet?

Maybe I will PM Mark Hammer for his thoughts incase he isn't reading this thread.

That's a good idea - I can breadboard/build this stuff but I don't fully understand the hows and whys. I have no doubt that the envelope follower could be improved by someone like Mark who understands what's going on.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 22, 2009, 07:57:29 PM
The envelope follower you used is a standard approach to the problem. I think that Oranges problem lies either in an incorrect value or maybe a miswire somewhere. I just ran some simulations on the circuit and it does its job as it should. I'd recommend for Orange to double check values first (although I'm sure you have) and maybe try increasing the "attack" resistor value to 100k or larger to see if that slows down his dV/dt (change in voltage over time) enough to prevent the popping. Anything under a few milliseconds and you're going to hear that audible "click/pop" at the output every time you hit the strings hard.

Frequency: It always helps to understand the circuits you design with, but it's obvious that you aren't all that lost. Understanding op-amp design is really not that hard once you understand a few limitations, and even those LM13700 OTA's aren't hard once you understand how a transconductance amplifier works. TBH, everything in your schematic is pretty dang standard and so explaining the circuit isn't as hard as you think. If you want, I can break it down for you in more detail than you'll care to know :D.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 08:08:42 PM
I am going to triple check this later tonight.  As for changing the attack resistor value.  Do you mean the 47k attack pot? or some other fixed value resistor?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on February 22, 2009, 08:51:57 PM
Got your note orange.  Your faith may be a little misplaced in this instance.  I'm reckoning Steve Giles is your man, but I will offer one suggestion: consider popping the NE5532 out and sticking a TL062 in, since that is what was originally used.  I'm also wondering if the resonance is too high.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 22, 2009, 10:58:46 PM
Mark,

The NE5532 is only in the output buffer (I am assuming that's a buffer!) and the voltage divider.  I have a tl081 in there right now though.

I retraced the schematic and redid the breadboard layout.  My 10k resistors measure about 9.75.  Maybe this circuit is really finicky with values?

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 12:49:01 AM
Rick, I am wondering which of the opamps in the schematic you used the tl062 and the lm324 for?  Is it possible that having the TL062 performing the function of a specific part of the circuit has something to do with the problem?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 23, 2009, 02:33:37 AM
I am going to triple check this later tonight.  As for changing the attack resistor value.  Do you mean the 47k attack pot? or some other fixed value resistor?

Yup. You can try making this pot value much larger, or put in different resistor values instead (like 100k, 470k, 1meg, etc..) and see if it helps anything out. You could have a bad pot in there, which would explain why you have so much attack that your filter pops. If that pot can't get over something like 100 ohms then you're most likely going to hear that pop.

I wonder if Rick'sbuild will pop if he turns the attack pot all the way counter-clockwise (or whichever way takes the pot to 0 ohms). Let us know by plucking the crap out of some strings!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: puretube on February 23, 2009, 06:49:15 AM
If anyone has any thoughts on specific areas of this circuit to check over, let me know!

The filter sounds great when it engages, but that darn pop!  Just like a loud static discharge!

The 10K resistor between the unity gain buffer and pins 1/16 of the 13700 is a critical value. The three resistors in that ara set the initial frequency of the filter. If that 10K is any lower you will have problems. Raise it and you will raise the initial frequency of the filter. You might try increasing the value a little - try 15K maybe. Also, play with the trimmer, mine is set halfway around at teh moment.

A little earlier in this thread Mark Hammer suggested a cap in series just before the range control - that might be a good idea, and maybe something I should experiment with on mine.

I`d implement the voltage divider at the input-side of the buffer... (but keep the 10k where it is!)

and remember, that any voltage applied to the 10k must exceed 2 diode-drops, before any current flows into pins 1/16...   :icon_wink:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 23, 2009, 01:25:29 PM
Frequency: It always helps to understand the circuits you design with, but it's obvious that you aren't all that lost. Understanding op-amp design is really not that hard once you understand a few limitations, and even those LM13700 OTA's aren't hard once you understand how a transconductance amplifier works. TBH, everything in your schematic is pretty dang standard and so explaining the circuit isn't as hard as you think. If you want, I can break it down for you in more detail than you'll care to know :D.

That would be awesome if you could actually Cliff - I can 'do stuff' with electronics but it's quite scary to me that I know how much I don't know - if that makes sense. I design with pre-existing 'blocks' and tweak on the breadboard. There is very little theory underpinning what I do. Scary huh? I probably understand tubes more than I do opamps.

Rick, I am wondering which of the opamps in the schematic you used the tl062 and the lm324 for?  Is it possible that having the TL062 performing the function of a specific part of the circuit has something to do with the problem?

In my pedal the output buffer and the unity gain buffer are the TL062.

BUT

When I breadboarded it I used two LM324's. I only used the TL062 in the final build.

Thinking it through though, it was only in the final build that I replaced the resistor between the unity gain buffer and pins 1/16 of the 13700 with a 10K. It had previously been 22K I think. So maybe a TL062 gives out less current than a LM324? And therefore needs a smaller current limiting resistor? The 22K that I replaced was holding the filter too 'open'. So maybe you should try a few different values in that position.

Having played about with this pedal for a couple of months, I have to say I just love the sound of it, some great stuff can be coaxed out of it. It is THE FUNK. I knew I would like it before I built it - I've been putting guitars through synths for years, and have a very similar Oberheim SEM multimode filter in one of my modular synths. But 'coaxed' is the operative word. It's a very 'touchy' device, and needs to be set up just right to get the good sounds. That means not only how all the knobs are set, but also which guitar you use, which pickup (bridge or neck), how the guitar's volume and tone are set, and which effects come before it. I would not dare to tweak in a sound on the fly in a live-on-stage situation. The only way I would consider using it live would be to have it on its own loop with a dedicated distortion before it, and set both up beforehand and not touch either apart from to stomp it in and out on the a/b switcher. Maybe it's the nature of envelope filters - a guitar really being an 'imperfect source' to derive gate and control voltages from.

I had a brainwave re the envelope follower this morning. I'm thinking of maybe dropping a couple of clipping diodes in just before the range control. I have this idea that the follower works better with a clipped waveform, so adding the clipping diodes would do this, particularly if the gain stage before the range control was increased from x100 to x1000 by replacing the 10K to vref with a 1K. It would be kind of like having a Distortion+ before the follower. I don't know if it will work out but I'll try it. I've try it when I get some time - I have two tube builds to finish this week.

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 05:21:16 PM
Well folks, I have tried a larger pot for the attack pot.  No luck.  Most of the travel does nothing.  The 50k is right.  Tried increasing that 10k resistor to pin 1/16 of the lm13700.  No luck there either. 

I love the sound of this filter once engaged.  It has a really good feel.  I just wish we could solve this problem!  How can this possibly be!  Rick, there must be some magic in yours!

Cliff or anyone else out there, would you breadboard this and see if you can get it to work properly for guitar?

Something I thought I would add is that once you get past that initial volume jump/pop, the filter if fine, but then if you don;t play, and the envelope closes so so speak, you have to pluck to get back in.  Mind you, if you pluck the strings and open the envelope, you can hear a slight hissing in the background and you can actually hear the envelope closing.  when it finally closes, you get a lower thump sound.  Not as loud as the pop when you engage.

Damn!  This thing is frustrating me to no end, but it sounds soo good once engaged!

Rick, you used all lm324's to breadboard.  Hmmm... so there isn't anything there then I guess...

Anyone want to breadboard and team debug?  I unfortunately don't know enough about envelope followers to debug this myself.

Would it help to post sound clips?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 23, 2009, 05:31:15 PM
Well folks, I have tried a larger pot for the attack pot.  No luck.  Most of the travel does nothing.  The 50k is right.  Tried increasing that 10k resistor to pin 1/16 of the lm13700.  No luck there either. 

I love the sound of this filter once engaged.  It has a really good feel.  I just wish we could solve this problem!  How can this possibly be!  Rick, there must be some magic in yours!

Cliff or anyone else out there, would you breadboard this and see if you can get it to work properly for guitar?

Something I thought I would add is that once you get past that initial volume jump/pop, the filter if fine, but then if you don;t play, and the envelope closes so so speak, you have to pluck to get back in.  Mind you, if you pluck the strings and open the envelope, you can hear a slight hissing in the background and you can actually hear the envelope closing.  when it finally closes, you get a lower thump sound.  Not as loud as the pop when you engage.

Damn!  This thing is frustrating me to no end, but it sounds soo good once engaged!

Rick, you used all lm324's to breadboard.  Hmmm... so there isn't anything there then I guess...

Anyone want to breadboard and team debug?  I unfortunately don't know enough about envelope followers to debug this myself.

Would it help to post sound clips?

Are you using active pickups or sending a LOT of signal to the filter pedal (maybe with a preamp?) then the envelope follower would be overly sensitive and rise too fast (causing that impulse I talked about earlier and hence, a pop). Op amp choice isn't very critical in this circuit to be honest, the only reason to use a TL0XX series FET is for the ultra high impedance that the LM13700 filter sections feed. The really high impedance presents no loading of the OTA based filters and is a common approach.

Another problem could be that 2.2 uF cap. Is it really 2.2 uF? Maybe take a picture of your build as it is on the breadboard. Also, sound clips never hurt either ;).
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 05:35:05 PM
I am playing a stock American Standard Strat.

I have a 2.2uF yes.  I tried a larger cap.  4.7 I think or 10uF.  Have to try that again.  I am pretty sure that is not it.

I will record some soun clips.

An a pic of the breadboard...  sure.  I am not a very neat breadboarder.  But I assure you I have built it as per the schemo.

Sound clips in a bit.  Maybe in the next couple of hours.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 23, 2009, 05:42:19 PM
What about double checking that all the vref points and ground points are actually correct? It's easy to connect a vref point to ground by mistake. For example, if you were to connect the 100k in the 220K/100k voltage divider (at pins 1/16 of the 13700) to vref instead of ground it would screw things up.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 06:00:22 PM
I will check that, but I am pretty sure of myself here.  I am going to upload some photos/sound clips in a sec.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: slacker on February 23, 2009, 06:08:54 PM
I`d implement the voltage divider at the input-side of the buffer... (but keep the 10k where it is!)

and remember, that any voltage applied to the 10k must exceed 2 diode-drops, before any current flows into pins 1/16...   :icon_wink:

I think this is the problem causing the thump, I simmed the envelope follower and the 200k/100k voltage divider are pulling the voltage down to 3-400mv. This means the filter will be completely closed and will suddenly jump open once the voltage output of the buffer reaches a certain point. Moving the divider like Puretube suggests solves this.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 23, 2009, 06:11:49 PM
I`d implement the voltage divider at the input-side of the buffer... (but keep the 10k where it is!)

and remember, that any voltage applied to the 10k must exceed 2 diode-drops, before any current flows into pins 1/16...   :icon_wink:

I think this is the problem causing the thump, I simmed the envelope follower and the 200k/100k voltage divider are pulling the voltage down to 3-400mv. This means the filter will be completely closed and will suddenly jump open once the voltage output of the buffer reaches a certain point. Moving the divider like Puretube suggests solves this.

That's interesting Ian (and Ton) - thanks for the input. Though I'm a little perplexed as to why mine doesn't thunk!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: slacker on February 23, 2009, 06:20:18 PM
Not sure, it could be down to the opamp used. Your envelope follower might be putting out a higher voltage at rest so the divider won't pull the voltage down as far.
You could measure the voltage at the output of the buffer and the control pins of the LM13700 and see how they compare with orangetones'.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 23, 2009, 06:37:01 PM
Not sure, it could be down to the opamp used. Your envelope follower might be putting out a higher voltage at rest so the divider won't pull the voltage down as far.
You could measure the voltage at the output of the buffer and the control pins of the LM13700 and see how they compare with orangetones'.

My pins 1 and 16: 1.025v
Orangetones      : 0.522v

My buffer output: 0.655v
Orangetones     : 0.055v

Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: slacker on February 23, 2009, 06:59:50 PM
Looks like that's the problem then, your control pin voltages are Ok, but oranagetones' are too low.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 07:07:59 PM
So moving the voltage divider to the input of which buffer are we taking about?  the unity gain one?  So I basically put the voltage divider on the + input of that buffer where the 2.2uF is connetced?

Pardon my ignorance here guys, I am still learning all of this.  I really do appreciate the help.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: slacker on February 23, 2009, 07:16:59 PM
Yeah that's it.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 23, 2009, 08:19:12 PM
Moved the voltage divider.  Now the envelope is not being held shut, however, having the voltage divider there seems to affect the controls (specifically the attack and release).  I had to change out the release pot for a 50k, and even then much of it is unusable, as the filter stays open and won't close for most of it's travel.  Have to try a lower pot.

Slacker, is there any way other than moving that divider to the input to get the envelope not to be held shut?  The functionality of the envelope follower is not as good as before.

I do have to play around with this a bit more, but I can say that the loud popping is gone.

Thoughts on the issue of moving this voltage divider and the other issues that it creates?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on February 23, 2009, 11:09:55 PM
I`d implement the voltage divider at the input-side of the buffer... (but keep the 10k where it is!)

and remember, that any voltage applied to the 10k must exceed 2 diode-drops, before any current flows into pins 1/16...   :icon_wink:

I think this is the problem causing the thump, I simmed the envelope follower and the 200k/100k voltage divider are pulling the voltage down to 3-400mv. This means the filter will be completely closed and will suddenly jump open once the voltage output of the buffer reaches a certain point. Moving the divider like Puretube suggests solves this.

You could move the bias resistors, but I don't see why the 10k resistor isn't just eliminated in the circuit, it really doesn't provide any useful service here (well, aside from current limiting!). Instead, remove the 10k resistor and place in a 100k resistor in the same spot, remove the other 100k resistor (the one going to ground) and leave the 220k resistor where it is. Essentially, you instead have a 100k resistor in series from the op amp output to the Iabc pins, and the 220k goes to VCC from the Iabc pincs (this acts as a voltage divider AND pulls the Iabc pin up to the correct voltage). In the case of what I describe in this post,  it's at about 1.8 V which keeps the filter on and hopefully pop free. The dynamic range of the filter (for a given envelope peak value, that is) can be increased by decreasing the 100k and 220k resistor values (forces more current to charge that cap to Vref) but if you're happy with the range, then stick with these values. If you guys want a schematic, let me know.

Frequency, you should give your components designators (R1, C13, Q3, IC3, etc..) so I can actually describe the changes I'm implying!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 24, 2009, 02:01:50 AM
Frequency, you should give your components designators (R1, C13, Q3, IC3, etc..) so I can actually describe the changes I'm implying!

Yes I should - lesson learned!

Orangetones: looks to me that tweaking the values of the voltage divider (in its original position) is the answer. Try changing the 100K for 250K pot, and tweak the pot until you get good sounds but no thunk - your voltages should be closer to mine then anyway. Measure the resistance across the pot and replace it with a fixed resistor.

Or maybe even replace the 220K/100k with a 1M pot, lug 1 @ +ve, lug 2 @ pins 1/16, lug 3 at ground, and tweak for the correct ratio soundwise and voltage wise. Measure and replace with fixed resistors.

Yours is so close to working correctly. The key must be in getting that voltage divider ratio corrent so your voltages are closer to mine at pins 1 and 16. I've gone over and over the schematic for errors, and taken my unit apart to check values. I am stymied by the variation between yours and mine, but ultimately the solution will be there for future reference. I have no doubt you will conquer it today.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on February 24, 2009, 06:14:46 PM
Well folks, I tried the 100k straight off the buffer like Cliff suggested, with the 220k going to vcc.  No dice.  Held it to much open.

Put in a pot to use as a voltage divider in place of the 100k/220k voltage divider.  Can set the voltage just right so that I get Rick's values.  But I still get a light thud as the filter closes.  As well, when I set pins 1 and 16 for 1.025 volts, I only get 0.385v on the output of the unity gain buffer.  So I guess I really didn;t match Ricks voltage there.

The other pots when the filter is held just open enough to avoid the popping (by using the voltage divider pot) jst don't seem to function very well.  The envelop filter is some how not working as nicely as when it was popping to open.

Strange...  I am starting to think that this thing may be more trouble than it's worth.

I would still be interested to have someone else breadboard this and see if they can get it to work stock with their components.  Cliff? Slacker? anyone?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: liquids on March 23, 2009, 10:29:23 PM
It may take me a while, but I'm dying for a synthy filter, and this looks feasible...count me in.

Only, tell me...I'm a big fan of reverse sweep.  For after I get it functioning as is (if!), tell me - what would be needed for a reversed sweep if at all possible--which I find more synthy than the typical sweep.   :icon_twisted:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 24, 2009, 03:27:32 AM
It may take me a while, but I'm dying for a synthy filter, and this looks feasible...count me in.

Only, tell me...I'm a big fan of reverse sweep.  For after I get it functioning as is (if!), tell me - what would be needed for a reversed sweep if at all possible--which I find more synthy than the typical sweep.   :icon_twisted:

You just need an inverted envelope to do that, a single extra opamp would do the trick, plus a toggle switch to select normal/inverted.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on March 24, 2009, 07:35:31 AM
Liquids, have you thought of trying the MXR Envelope filter from Tonepad?  There are mods for it to do different ranges and reverse sweep.  It is a pretty versatile filter.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on March 24, 2009, 08:13:45 AM
I would be interested to see a combination of your filter with my sweep generator from the Space Filter, which is dying a death out there!

http://www.4shared.com/file/89784300/b7d68e64/Space_Filter_S__H.html

I think there might just be a little more scope. What do you think Cliff Schecht?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: liquids on March 24, 2009, 08:17:23 AM
I've thought about it.  I don't have sound samples though, so it's hard to get excited unless I know.  I had a filter that I believe was based on the MXR.  It didn't have that aggressive resonance I'm actually most interested in, which even the mutron/q-tron circuit I have only begins to approach.  I'm really most interested in the filter section of the EH Microsynth (StephenGiles Space Filter is a big interest, but I lack some parts and the debugging skills to do that, for the time being)  or an MS-20/Funk-a-duck thing!  From the sound samples, this is aggressive enough and looks doable, so it will scratch part of the itch.

Maybe the MXR is more aggressive than I'm thinking, though, anyone got samples?  I'll search.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on March 24, 2009, 11:07:50 AM
I've thought about it.  I don't have sound samples though, so it's hard to get excited unless I know.  I had a filter that I believe was based on the MXR.  It didn't have that aggressive resonance I'm actually most interested in, which even the mutron/q-tron circuit I have only begins to approach.  I'm really most interested in the filter section of the EH Microsynth (StephenGiles Space Filter is a big interest, but I lack some parts and the debugging skills to do that, for the time being)  or an MS-20/Funk-a-duck thing!  From the sound samples, this is aggressive enough and looks doable, so it will scratch part of the itch.

Maybe the MXR is more aggressive than I'm thinking, though, anyone got samples?  I'll search.

No samples for Space Filter as I have failed Gordon Brownly  :icon_biggrin: to get a filter section to work with the sweep generator :icon_rolleyes:  - not that I've really spent that much time on it. The Multimode filter clearly works. I would prefer to have 2 filter sections in parallel to give a more throaty vocal sound, as in the Bifilter follower. The envelope follower is fine on "funk a duck" sounds which I personally can't stand, but on longer sweeps suffers from bad ripple. This is why I think the LM13600ified Space Drum sweep generator will provide a smooth long sweep - because it does to the VCO in the Space Drum.

I'm busy for the next few days so someone might like to have a go. 
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on March 24, 2009, 12:03:22 PM
The Multimode filter clearly works.

Well...  I tried my hardest to get this thing to work on the breadboard and still, it didn't work like the sound samples posted by freq. central.

Has anyone else breadboarded this and gotten it to work properly?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 24, 2009, 12:53:43 PM
I would be interested to see a combination of your filter with my sweep generator from the Space Filter, which is dying a death out there!

The Multimode filter clearly works.......The envelope follower is fine on "funk a duck" sounds which I personally can't stand, but on longer sweeps suffers from bad ripple. This is why I think the LM13600ified Space Drum sweep generator will provide a smooth long sweep - because it does to the VCO in the Space Drum.

I'd be interested it that too Stephen, and I for one follow every post on the Space Filter thread. My Multimode sounds great (though I can't claim to have designed it), though I'd have to agree that it ripples badly on long sweeps, I'd love a follower that was more forgiving.

I've got an idea that a leading edge envelope detector would be the way to go: http://www.diystompboxes.com/smfforum/index.php?topic=73059.msg592144#msg592144
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: liquids on March 29, 2009, 07:40:48 PM
Well...  I tried my hardest to get this thing to work on the breadboard and still, it didn't work like the sound samples posted by freq. central.

Has anyone else breadboarded this and gotten it to work properly?

I finally breadboarded it - it's was the one thing I wanted to do before I go away for a few days tomorrow.  Sad to say, nearly no success.  Man, is that an eyesore on the breadboard.  :D Something like this, it seems breadboarding it once and then starting over is a good thing, so you can visually know what kind of space you need and where when you do, to keep it clean and neat. 

Anyhow, I've gotten it to pass a signal, one that is oddly distorted. My voltages on the LM13700 match yours Rick, dropped to 9.48v, other than your voltage on pin 15, which I thought was supposed to be not connected to anything--thought you list 5.99V on that pin :D Oops?

I double checked all my connections and audio probed, etc, preliminarily, but no luck. I Can't check my voltages on the op-amps because I used a different op amps and also the most sensible section of the quad op amp to use, rather than following the layout posted.  I also need to solder up some more pots for breadboarding for this one. I'm lacking the LM324 that this, the original circuit, and the Space Filter seem to request...time to do an order, methinks....

The LED test proved simply to light up constantly.  DMM on pins 1/16 showed no voltage change when playing, so there is something happening there. I don't understand the envelope section...maybe I will replace it with a simpler one? The only thing that I have to show for it, is that when I disconnected the 10K from the buffer going toward pin 16, I could hear the filter set manually and the resonance pot affected the sound.   I'll mess around for fun the rest of the night and then maybe start over when I get back next weekend.  :-\
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 30, 2009, 03:43:43 AM
This does seem to be a problematic circuit. Strange. The way I work with new designs is to breadboard until I'm ready to build, then draw up a schematic from the breadboard, and build from that schematic, so the schematic I built from is the same one you built from. If you still want to experiment with this, can I suggest that you refer back to the circuit I based (stole?) my design on (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf), build it on your breadboard, test it works, then systematically modify it to my design. Thats how I did mine, it started off as the Synbal circuit, then I modified it. I will be relieved when at least one person has built it without issues, as I'm feeling big guilt at the moment for all the wasted man hours. Boogdish at least got the filter section working, though he hooked it up to a different follower.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on March 30, 2009, 09:25:39 AM
This does seem to be a problematic circuit. Strange. The way I work with new designs is to breadboard until I'm ready to build, then draw up a schematic from the breadboard, and build from that schematic, so the schematic I built from is the same one you built from. If you still want to experiment with this, can I suggest that you refer back to the circuit I based (stole?) my design on (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf), build it on your breadboard, test it works, then systematically modify it to my design. Thats how I did mine, it started off as the Synbal circuit, then I modified it. I will be relieved when at least one person has built it without issues, as I'm feeling big guilt at the moment for all the wasted man hours. Boogdish at least got the filter section working, though he hooked it up to a different follower.

I tend to draw a circuit as I go when breadboading, as it is a real pain to unravel a birds nest afterwards!!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: liquids on March 31, 2009, 11:48:46 AM
This does seem to be a problematic circuit. Strange. The way I work with new designs is to breadboard until I'm ready to build, then draw up a schematic from the breadboard, and build from that schematic, so the schematic I built from is the same one you built from. If you still want to experiment with this, can I suggest that you refer back to the circuit I based (stole?) my design on (http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths%20Drum%20Synths%20and%20Misc%20Synth/Synbal.pdf), build it on your breadboard, test it works, then systematically modify it to my design. Thats how I did mine, it started off as the Synbal circuit, then I modified it. I will be relieved when at least one person has built it without issues, as I'm feeling big guilt at the moment for all the wasted man hours. Boogdish at least got the filter section working, though he hooked it up to a different follower.

I've refered back the original circuit as a built and actually did start from scratch after I tried it first, for neatness, to the same result. I'm frustrated that I can't seem to get the envelope section...when I have the two parts connected, there is no filtering, but disconnecting that 10K resistor, I hear the filter, with the resonance pot sounding as if to finction more like a manual filter control...when set high, it's bright, set low it's muffled. Odd.

With the original circuit, it's hard for me to break it down into it's parts, though refering back to your schematic helps as many of the values of course are the same.   I don't mind the man hours, it's worth it to me, not a waste!  I'm going to give Stephen's space filter a shot next, but I'll come back to this maybe...I do have it sitting on my breadboard still, so maybe it depends on what itch I get.   :)

I have to confess as I hinted at earlier, that I didn't have all the pots breadboarded, and had some as preset resistors.  If you could post some good 'starting' points for the pots, since there are a few 'widely' variable values there that I can't even guess at.  Twisting them didn't do muchfor me though.  I did, for example have a decay set 'halfway' as a 470k resistor to ground the whole time....maybe that was throwing it off a bit.  I also ignored the HP/HP taps for simplicity and personal preference. 

I understand filter settings theoretically, but from your experience in particular, what are good values to start at here, say? Likewise, have you noticed preference for pickups type/pickup output/running a buffer?  Also, looking at the circuit, you have the signal running to the top part, the op amps (this is the voltage control section, correct?) bled off the (potentially unbuffered) input signal splitting also into the filter section (that is, the parts that hits one op-amp stage and then the LM13700 stages)?   
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Cliff Schecht on March 31, 2009, 02:19:47 PM
Something to remember with the LM13700 is that transconductance is a function of temperature and varies all over the board from one LM13700 to the next (although the two OTA's within one IC are matched well). This essentially means that the position of a pot for Rick's build might not work so well for you, especially if it's the envelope follower input offset potentiometer. The attack and decay pots can be just resistors, but the offset pot sets the initial position of the filter (a DC level that determines what the output current and hence the filter cutoff frequency). Since each LM13700 varies so much, this pot position won't be the same from one board to the next (plus you have to factor in 5% resistor tolerances and the 20% pot tolerances).
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on March 31, 2009, 04:22:34 PM
Something to remember with the LM13700 is that transconductance is a function of temperature and varies all over the board from one LM13700 to the next (although the two OTA's within one IC are matched well). This essentially means that the position of a pot for Rick's build might not work so well for you, especially if it's the envelope follower input offset potentiometer. The attack and decay pots can be just resistors, but the offset pot sets the initial position of the filter (a DC level that determines what the output current and hence the filter cutoff frequency). Since each LM13700 varies so much, this pot position won't be the same from one board to the next (plus you have to factor in 5% resistor tolerances and the 20% pot tolerances).

They won't notice that :icon_biggrin:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on March 31, 2009, 04:30:18 PM
They won't notice that :icon_biggrin:

What do you mean by this?  Who are they?  The chips? builders won't notice this information?

I had a devil of a time with this circuit.  If you are having trouble too, read back and see what I did and make sure that isn't the issue for you too.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Slade on April 19, 2009, 02:38:15 AM
They won't notice that :icon_biggrin:

What do you mean by this?  Who are they?  The chips? builders won't notice this information?

I had a devil of a time with this circuit.  If you are having trouble too, read back and see what I did and make sure that isn't the issue for you too.
Sorry, I didn't read all the pages before this, but I wanted to ask you if you have tried with a TL072 instead of the NE5532? I had a trouble with a NE5532 in a delay that later worked fine with a TL072...
Greetings ;)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on April 19, 2009, 04:22:57 PM
They won't notice that :icon_biggrin:

What do you mean by this?  Who are they?  The chips? builders won't notice this information?


Los fuzzboxerios!!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 06, 2009, 01:26:08 AM
Hey all,

Just a couple quick Q's :

1. How would I add led's like in Freq Centrals unit> For the HP, BP and LP modes?

2. I am almost done building 2 of these and wonder where I could put the blend control? Can it be off the pcb and would it just blend the dr input and the output?

thanks! :)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 06, 2009, 03:02:01 AM
Hey all,

Just a couple quick Q's :

1. How would I add led's like in Freq Centrals unit> For the HP, BP and LP modes?

2. I am almost done building 2 of these and wonder where I could put the blend control? Can it be off the pcb and would it just blend the dr input and the output?

thanks! :)

I used a double pole 3 position (DP3T?) rotary switch to select the filter mode/LEDs. The cathodes of all three LEDs are grounded, the anodes are connected to each of the three positions of the switch, the common of the switch is connected to +ve via a 1.5K resistor.

Not sure of the best way to implement a blend pot, but would guess just feeding the clean and effected signals into lugs 1 and 3 of a 22k Lin pot would do it, maybe with a single opamp buffr after it?

I'm using mine a lot, wedged in between a Big Muff (before the MF) and a Clari(not). The Clari is set to a fast slapback, and the fuzz distorts the filter ina really wild way. I'll post up some soundclips, it does sound awesome!

Good luck with your builds, I hope they work out, I'm beginning to feel this circuit is jinxed!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: sean k on May 06, 2009, 08:29:04 PM
Thanks for the links to the original FC!, I went and got all the rest of the synth drum pdf's as well and have been especially interested in the synblo which uses an air tube onto a crystal mic element to control envelopes.

Looking for crystal mics was interesting too and eventually I found a Utube vid of this guy who built one with a home grown crystal in a toilet roll with paper cellotaped over one end and a stick, or somesuch, between the paper and the piezo to affect the surface of the piezo.

I've only googled the synblo but I found a much better scan than the electronics anonymous scans.

I also quite like the 40106 and 4070 on the synbal and what I can see is, with my entirely limited knowledge (and I can't find my electro resource book) is that the 4070 is used as a mixer of sorts that as each gate goes high, or low?, it takes that signal. Cool! could be interesting as an LFO mixer  ???

Seems the earlier post where the LFO was applied to pin 1,16 of the OTA through an 800k resistor combined with running the envelope into an LED might be the best way to meld the operating point of the two functions.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 07, 2009, 12:46:16 AM
Well I have faith that mine will work. :)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 07, 2009, 02:57:12 AM
...faith...

That's what I use, far better than solder or book learning.  :icon_lol:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 09, 2009, 10:49:37 AM
I think I might have found the bug in this design. I just breadboarded the envelope follower for another circuit I'm working on. I used a 4558 for the two opamps that make up the envelope generator - and it didn't work. As soon as I changed to an LM324 for those two opamps it worked. Is that it? I hope so. Strange, I would have thought it would work the same with 4558s.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: slacker on May 09, 2009, 11:01:26 AM
I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 09, 2009, 01:09:47 PM
I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.

Thanks Ian, so what would have to change (and how) in that envelope follower to make it work with a 4558?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 12, 2009, 06:45:26 PM
I think I might have found the bug in this design. I just breadboarded the envelope follower for another circuit I'm working on. I used a 4558 for the two opamps that make up the envelope generator - and it didn't work. As soon as I changed to an LM324 for those two opamps it worked. Is that it? I hope so. Strange, I would have thought it would work the same with 4558s.

I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.

Thanks Ian, so what would have to change (and how) in that envelope follower to make it work with a 4558?

I did get my breadboard circuit using the 4558 to work by switching the 220K and 100K resistors (after the Range control) from ground to vref. This may affect the range of the output of the unity gain buffer after the detector, so the biasing of the resistors at pin 1 and 16 of the 13700 may need tweaking.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 13, 2009, 05:39:26 PM
Mine are being built off the pcb pdf. I think I should be fine. :)

I just need to get off my butt and order the lm13700's I need about 10 anyways. :icon_redface:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on May 13, 2009, 09:24:36 PM
Do let us know if you get it working off that PCB.  Others have not had any luck.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 14, 2009, 02:58:17 AM
UH OH!!!!!! :-[

Well once i get the lm13700's ill be bale to find out.

What seems to be the biggest issue? And when you say not working off the pcb, is not working in any way shae or form or does it kinda sorta work?

Damn! :-X
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: orangetones on May 14, 2009, 02:23:52 PM
My suggestion would be to go back and read through this entire thread.  If I am correct there was much discussion about the functionality of this project.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 14, 2009, 02:44:11 PM
Oh god...the read the thread answer....

Thats never good. :P :icon_cry:
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 14, 2009, 08:11:28 PM
My suggestion would be to go back and read through this entire thread.  If I am correct there was much discussion about the functionality of this project.

$h!t, am I going to have to build myself another to salvage my tarnished reputation? It's hardly rocket science - but a more complex build than a Fuzz Face!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on May 14, 2009, 09:43:24 PM
I just need some of those ota's to give mine a run through.

I have the ca3280's and if I knew how to do it, I would make some kind of converter board and just use those.

perhpas you should build another...but really for the purpose of having another filter. you can never have too many. And us bass players need cool diy pedals..NOt another ff or tonebender, or derivative. :)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: chicago_mike on July 08, 2009, 04:04:34 AM
Well I orderd my LM13700's and I have the LM324's and the tlo72 / 062's.

I was wondering if theres any progress on this project from others. :icon_smile:  I have the schematic for another ef that uses the 13700 but I would like to get this going first.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: T1bbles on January 23, 2010, 10:31:12 AM
Has anyone anywhere got this circuit to work yet? Other than the mighty Rick of course ;) I've sat for about an hour now switching between the schem and the PCB layout and it all seems to be right, unless I've overlooked something, which isn't unlikely!

It'd be a shame to have to give up, cuz this baby looks and sounds a beast!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on January 23, 2010, 10:52:24 AM
Development thread for a future version 2 with more features and less issues here: http://circuitworkshop.com/forum/index.php?topic=235.0
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: svstee on February 19, 2010, 05:32:22 PM
Anything new with version 2? Should I wait for it or build V1?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 19, 2010, 05:33:30 PM
Anything new with version 2? Should I wait for it or build V1?

Wait.............................
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: svstee on February 19, 2010, 06:37:06 PM
Awesome! Looking forward too it.  ;D
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Altitude on February 28, 2010, 05:25:52 PM
Greetings all. I've been lurking around here looking for a worthy filter for a expanded 8 bit sampler I am working on and this thing sounds like exactly what I am looking for.. In lieu of the issues with the envelope follower could it just be dropped and the filter run wide open permanently? For my needs, that would be fine. Frequency Central, you mentioned that someone else got this working with a different env design, can you elaborate?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 28, 2010, 05:29:06 PM
Greetings all. I've been lurking around here looking for a worthy filter for a expanded 8 bit sampler I am working on and this thing sounds like exactly what I am looking for.. In lieu of the issues with the envelope follower could it just be dropped and the filter run wide open permanently? For my needs, that would be fine. Frequency Central, you mentioned that someone else got this working with a different env design, can you elaborate?

Boogdish made three posts on page 2, including a vero layout for the filter section: http://www.diystompboxes.com/smfforum/index.php?topic=73021.msg593387#msg593387
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Altitude on February 28, 2010, 05:31:45 PM
Gotcha, thanks.

So just tie pin 1 and 16 and it will be "open"?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on February 28, 2010, 05:38:54 PM
Gotcha, thanks.

So just tie pin 1 and 16 and it will be "open"?

Yeah, you can use other stuff to modulate the filter then. Don.t forget a resistor between your modulator and pins 1/16.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: fuzzo on February 17, 2011, 02:08:25 PM


Yeah, you can use other stuff to modulate the filter then. Don.t forget a resistor between your modulator and pins 1/16.

this is the only change we have to do to put another enveloppe controller ?

I bump this old thread 'cause I'm thinking about building that kind of filter but I'd like to put a enveloppe detector with an Up/down switch (I think using the one in the old yellow boss (don't remember the name))

I've a question to people who built that circuit , Does the resonance control bring a volume boost ? (this is for an old box I drilled years ago and never found a circuit to put in (tired of fuzz/Od/boost) so I'm limited on knob holes)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Stabby on March 09, 2011, 04:47:05 PM
I would love to build this filter too, but for keys instead of guitar. What should be changed to optimize this filter for line level?

I would like to work with a pedal as well, so could I just leave out the entire opamp section? (except the LM13700 of course)
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 09, 2011, 05:08:24 PM
I've used mine with my Rhodes (I know you're a Rhodes player) going directly in, the Rhodes is after all closer to guitar levels than keyboard levels. Now, Rhodes >> overdrive >> Funky MF is somethin' else ;) Just be warned, many have had issues with this circuit. I should probably revisit it and breadboard it again......maybe build another.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Stabby on March 09, 2011, 05:13:02 PM
Hey, you remember me! :)

I don't have a Rhodes myself. I wanted to build a pedal for my cousin who has one. I play on a Yamaha Motif myself though which is line level.

Here's a schematic of the Korg MS20 filter (which uses the LM13700) for line level:

http://www.synthforum.nl/forums/showthread.php?t=138512

There are some demos as well in the link. It's proven to work for everyone. It's just LP and HP though. Any idea what to change to make it a bandpass filter?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 09, 2011, 05:43:35 PM
Yeah, Rhodes players are rare around these parts!

How you go from lowpass to bandpass to highpass is all a matter of phase cancellation. Some multimode filters do it by where they put the input (ie Synthacon) others do it by where they take the output from (ie Oberheim SEM).

I'd certainly think the Escobedo LPF could be modified easily to do bandpass. Take a look at it's two seperate feedback loops - pin 4 > pin 8, pin 13 > pin 9, I'd hazard a guess that if you just had a single loop, pin 4 > pin 9 you could take a bandpass tap from pin 8.

BTW, the Funky MF filter does work well, the filter part anyway, any build issues seem to lie with the envelope section and the use of LM324. Like I said, the design is due an overhaul, I'm haunted by this thread - it reappears every so often I think to myself there's gotta be a redesign soon.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on March 11, 2011, 04:01:00 PM
I'd certainly think the Escobedo LPF could be modified easily to do bandpass. Take a look at it's two seperate feedback loops - pin 4 > pin 8, pin 13 > pin 9, I'd hazard a guess that if you just had a single loop, pin 4 > pin 9 you could take a bandpass tap from pin 8.

In fact, looking at the state variable filter on the LM13700 data sheet, disconnect the 220k resistor from pin 13 (on the Escobedo lowpass) and connect it to pin 4 instead. Pin 8 will then give you a bandpass output.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Pakaloabob on March 12, 2011, 01:09:21 AM
...Like I said, the design is due an overhaul, I'm haunted by this thread - it reappears every so often I think to myself there's gotta be a redesign soon.
Ha Ha! I have been watching this thread for quite a while, waiting for the project to move forward.  I haven't attempted it even on the breadboard yet because you yourself (Rick) said it was a "problematic circuit." That scared me  :o
And this post:
Anything new with version 2? Should I wait for it or build V1?

Wait.............................
Really got me intrigued...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: The_Armadillo on November 16, 2011, 08:15:17 PM
Does anybody have a perf layout for this? I'm not really into etching, and I've never gotten a good result out of it.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Caramthros on June 27, 2012, 05:11:06 PM
Is there a working PCB that I could buy or has someone designed a stripboard layout that I could use.

Found this today and want to make an envelope filter for my bass but on the cheap. This seems suited for my price range :D
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Masuto on May 30, 2013, 01:33:24 AM
Layout! Layout! Layout! Layout! Layout!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Ben N on June 04, 2013, 03:22:19 PM
Sentence, sentence, sentence!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Joe Viau on July 29, 2013, 11:36:32 PM
Has anyone built this?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: sshrugg on August 21, 2013, 03:29:40 AM
Is there a way this pedal could be controlled with an expression pedal like a conventional wah?  I happen to have an enclosure from a broken pedal that includes expression...

I've always wanted to build this.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: StephenGiles on August 21, 2013, 01:43:12 PM
Is there a working PCB that I could buy or has someone designed a stripboard layout that I could use.

Found this today and want to make an envelope filter for my bass but on the cheap. This seems suited for my price range :D

I have never needed a layout for any of my stripboard builds - you just practice!!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: sshrugg on September 25, 2013, 04:42:00 AM
Sorry to pester, but...bump?

Is there a way this pedal could be controlled with an expression pedal like a conventional wah?  I happen to have an enclosure from a broken pedal that includes expression...

I've always wanted to build this.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on May 04, 2016, 10:29:47 PM
Back from the dead.
This gives you an idea of just how many populated boards I have lying around that still need to be debugged and wired up.

The circuit works fine for me...sometimes...and soimetimes not.  It behaves very well and sounds terrific if I play a bunch of notes and don't give it a chance to come to rest.  But if I do, the thing produces a jarring thwap at the start of the next notes I play.  It ceases to be a filter that stands up, sits down, and stands up again.  Rather, it behaves like a guy sleeping under a pile of beer cans who suddenly jumps up.  The artifact is not dependent on Range or Resonance settings, but entirely on how long it has been since the last note plucked.

I can hear a bit of it in the ticks at the start of some notes in the soundclip Rick provides very early on in this thread, except its worse in my case.  For a moment I thought it may simply be a bad electro providing an unstable Vref, but I replaced it and that made no difference.

I'm stymied.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: avandelay on May 05, 2016, 05:16:19 PM
I built this filter last night on breadboard and it works great.  I am building a groovebox with current controller oscillator and the filter sounds amazing.  I dont really know how the envelope section works, technically speaking, but I am hoping to be able to trigger the envelope with a clock signal.  Anyone have any ideas about that?  I don't have any gate control, so I have many tied notes which of course do not trigger the envelope.  Of course I can mute a step and the following note will trigger the envelope.  I could introduce some very cool rhythmic variation if I could use a clock signal.  Any help would be much appreciated!
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on May 05, 2016, 07:21:44 PM
I agree.  It sounds very good...when it sounds good.  If you listen to Rick's soundclip - http://www.aronnelson.com/DIYFiles/up/Funky_MF_Bass.mp3 - around the 10-second mark you'll here this godawful click/pop at the start of each note.  I wish I knew how to prevent it on my build, because it spoils an otherwise excellent filter.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: avandelay on May 16, 2016, 04:11:59 PM
Mark, are you using the filter for guitar?  I am using it with a synth, and I can replicate the annoying pop within certain parameters which probably line up pretty well with the range and style of a guitar player.  I agree it is pretty bad in those spots.  Seems to have to do with the overlap of the attack and release...
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: frequencycentral on May 16, 2016, 05:19:24 PM
In hindsight, I think it may be down to the envelope sweeping the filter too widely, perhaps it needs limiting. I've built the filter part as a +/-12v module with no issues. Th  problem must be the envelope.

If I recall the envelope was a rail to rail LM324, the LM13700 certainly can't handle rail to rail signals. Perhaps swapping the LM324 for a TL084 would be a good place to start? I'll have to dig out that old pedal sometime and give it a whirl.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on May 16, 2016, 07:29:34 PM
Thanks for chiming in, Rick.  I'll unsolder the 324, socket the space, see if it behaves any better with an 084, and report back when done.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on May 16, 2016, 10:11:42 PM
Well, I tried a few different quads: a TL084, a TL054, an LM348, and a an MC3403.  The 3403 was the best-behaved of the lot.

I should add, better than the LM324.
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: avandelay on July 03, 2016, 04:34:39 PM
The "volume" opamp and pot seem to only add gain.  I would like to eliminate the gain.  Can I eliminate that whole opamp or does it serve another purpose and should I just bridge across where the pot is located?  I'd experiment but it's already soldered up.  Thanks for any advice.

Jeff
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on December 20, 2019, 03:39:39 PM
Pulled it out again today to take another stab, as I slowly work my way through the bin of things that came close to working but not close enough to box up.

Yup, bi-fet quads don't work at all.  I used my last 3403 for an OD-1 clone so I can't reproduce what it did, but a second stab at using different Bi-Fets was unsuccessful.  Put the 324 back in the socket, and it worked again but has the same issue, namely that there is a very pronounced thunk at the onset of each sweep.  Additionally, if the resonance is set higher, it will "lock up" and emit a high-pitched oscillation that won't stop until I turn the sensitivity/Range control was turn way down.  Perhaps that can provide some clues as to what is causing the misbehaviour.  Could the 220k/100k pair providing a bias/offset to the control current be a possible solution?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: rankot on December 20, 2019, 05:26:05 PM
Schematic in the first post seems to be dead. Anyone can repost?
Title: Re: "Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter
Post by: Mark Hammer on December 20, 2019, 07:17:33 PM
Here's what I'm working from.  Note that one stage shown as assigned to the TL062 is actually assigned to the LM324, and vice versa.
(https://i.imgur.com/7HCKyMw.jpg)