Hi All,
I'd like to show you what I've been messing about with the last week or so. It's a vactrol-controlled state variable filter inspired by the Mutron, but actually owning more to the SVF design on the ESP pages than the original Mutron circuit. The control signals for the vactrols come from one of my PIC-based LFOs, so I've got tap tempo and eight waveforms to choose from. The waveforms are:
(https://electricdruid.net/wp-content/uploads/2018/03/STOMPLFOWaveforms.png)
The prototype is not the most beautiful thing you've ever seen, but it's functional enough:
(https://electricdruid.net/wp-content/uploads/2018/03/DSCN6014.jpg)
The dangly red wire on the RHS is the highpass/bandpass/lowpass selector. I hadn't got a suitable switch handy (I was asking about this in another thread). The vactrols are VTL5C3's. There are Xvive clones of these that aren't too expensive and are pretty widely available. Or roll your own, obviously.
The schematics are here:
https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg1.jpg (https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg1.jpg)
https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg2.jpg (https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg2.jpg)
Finally, here's some sound samples.First, a basic funky riff with some lowpass autowah:
https://electricdruid.net/sounds/filterfx/Funky1.mp3 (https://electricdruid.net/sounds/filterfx/Funky1.mp3)
Next, something similar, but with highpass filtering taking all the fundamental out (mostly with the Ramp Up waveform):
https://electricdruid.net/sounds/filterfx/Funky3HP.mp3 (https://electricdruid.net/sounds/filterfx/Funky3HP.mp3)
A lead solo with lowpass filtering using the Random Slopes waveform for a less repetitive wahwah effect:
https://electricdruid.net/sounds/filterfx/LeadLPSH.mp3 (https://electricdruid.net/sounds/filterfx/LeadLPSH.mp3)
Some rhythm guitar with lowpass and then highpass filtering using the Random Levels "sample and hold" waveform. This can get pretty abstract:
https://electricdruid.net/sounds/filterfx/RhythmLPHP.mp3 (https://electricdruid.net/sounds/filterfx/RhythmLPHP.mp3)
Finally, some strumming and playing about with the different waveforms available and fiddling with the Rate and Depth knobs a bit. This is wild filter mayhem:
https://electricdruid.net/sounds/filterfx/StrummingWaves.mp3 (https://electricdruid.net/sounds/filterfx/StrummingWaves.mp3)
I've got a few tweaks to do to it perhaps. For example, I can't decide whether to add a trimmer to the first op-amp to provide some gain if necessary. The trouble with that is then you'd probably need another trimmer on the output to compensate. Also the current 5 knobs+ one switch is too many knobs, and I'm thinking that swapping the Resonance knob for another three-position switch (high/mid/low res) would be better, since I pretty much only ever use the maximum position anyway.
All thoughts, comments, and improvements welcomed!
Tom
Sweet Tom.
Is that with the new 8pin dip lfo chip?
I need to try those.
Rich
Quote from: Kipper4 on March 19, 2018, 04:21:34 PM
Is that with the new 8pin dip lfo chip?
It is indeed - the "StompLFO". Some years ago there was a discussion on here about an 8-pin PIC LFO, and a couple of other people did one, but I never got around to it until this winter. It's looking like it might be a handy little chip. I'd like to do a simple tap tempo tremolo with it too. The original TapLFO is great n'all, but pedals based on it tend to finish up with about two dozen knobs for all the options. So a slightly simpler and less tweaky version for people who actually want to play the guitar instead of twiddling. And I'd love to try it for a chorus - especially with the two random waveforms.
Quote
I need to try those.
What can I say? *Everyone* needs to try those! ;) lol
Tom
Thought for a sec that the second knob was labeled "Druid Rate", which had me stumped. Shows that I need to read all of the labeling before trying to figure out what each knob does. :icon_lol:
Sounds nice. What would put it over the top would be expression-pedal control, and/or envelope control.
This is exactly what I've been looking for. Exactly, right down to the random LFO.
Untiiilllll... I saw the lightwah, with that optical control. I for one do not want a separate expression pedal. I guess I have two piorities - filter w random LFO, and I'm never going to have a wah pedal on my board. Just the real estate. Obviously this isnt everyone's cup o'tea. Is an open LDR light-controlled wah even remotely consistent? The Lightwah is a late entry into my list of considerations. I'm sure I could build it into this. (If I did, I wonder how this would compare to the light wah?)
Sync input-nice! External LFO? External trigger might be interesting too.
I don't know about front end gain control, but don't you think output volume will be necessary? I'm sure some sounds can jump out and bite you.
Here's an idea - should a pedal such as this, which may enjoy being placed before a fuzz face like few others, have a cheap little transformer based pickup simulator - inside the box? Switchable?
Can I say this? I've asked smallbear to get the LFO chips. Very excited about them. Heck, I was very excited about building the LFO from scratch, but this is wonderful.
One more edit - how does the speed control affect the "random" waveforms? Hopefully it does.
Quote from: Mark Hammer on March 19, 2018, 06:42:15 PM
Sounds nice. What would put it over the top would be expression-pedal control, and/or envelope control.
Thanks Mark.
Expression pedal is easy, envelope control is a whole other thing.
For the expression pedal, you can wire the Freq/Offset pot via a stereo jack so that inserting an expression pedal takes over from the existing pot. Since the PIC isn't fussy about the pot value it should work with pretty much anything. Also the jack provides the +5 and ground connection, so you don't need a CV pedal, although you could wire it for one of those too if you wanted.
Of course, you could add an envelope follower too, but I was desperately trying to keep it simple!
Tom
Quote from: blackieNYC on March 19, 2018, 07:04:39 PM
Sync input-nice! External LFO? External trigger might be interesting too.
Yeah, one thing I haven't tried yet is syncing it up to a synth sequence, but I shall give it a whirl. The LFO will sync to incoming pulses.
Quote
I don't know about front end gain control, but don't you think output volume will be necessary? I'm sure some sounds can jump out and bite you.
Maybe you're right. Pity, I'm trying to keep the knob-count under control, not add more. Oh well! ;)
Quote
Here's an idea - should a pedal such as this, which may enjoy being placed before a fuzz face like few others, have a cheap little transformer based pickup simulator - inside the box? Switchable?
Easily added if that's your objective, for sure.
Quote
Can I say this? I've asked smallbear to get the LFO chips. Very excited about them. Heck, I was very excited about building the LFO from scratch, but this is wonderful.
Cool, thanks. I'll make sure we get some winging their way!
Quote
One more edit - how does the speed control affect the "random" waveforms? Hopefully it does.
Yes, it does. The LFO rate is used as an underlying clock in both cases, and every time the clock "ticks", a new random value is chosen. For the random level, that value becomes the output until the next tick. For the random slope, the chip does a linear interpolation between the last value and the new one until the next tick.
So in both cases, you have some control over how rapid/frantic the sound is, but no control over the detail.
Tom
Quote from: ElectricDruid on March 19, 2018, 08:53:25 PM
Quote from: Mark Hammer on March 19, 2018, 06:42:15 PM
Sounds nice. What would put it over the top would be expression-pedal control, and/or envelope control.
Thanks Mark.
Expression pedal is easy, envelope control is a whole other thing.
For the expression pedal, you can wire the Freq/Offset pot via a stereo jack so that inserting an expression pedal takes over from the existing pot. Since the PIC isn't fussy about the pot value it should work with pretty much anything. Also the jack provides the +5 and ground connection, so you don't need a CV pedal, although you could wire it for one of those too if you wanted.
Of course, you could add an envelope follower too, but I was desperately trying to keep it simple!
Tom
Well, anything that would provide some real-time control is fine by me. So what you describe nails that.
As well, looking at then datasheet, I see that the 4 different parameters are voltage-controlled. Sounds to me like a job for my Source Audio Hot Hand 3! Those units output 0-3.3V control voltages.
Ever tinkered with using discrepant fixed-resistor values for the two vactrol stages in the filter, like Lovetone did with the Meatball? They used a higher-value resistor in parallel with the vactrol/LDR for the first one, and lower value for the 2nd. I can't say that I've ever heard equal-value resistors (the traditional arrangement, which you use) directly compared against discrepant-values.
Sounds excellent! This would give me a great excuse to get one of your flanger boards ( and/or delay boards )
with the filterfx pcb ( when it's ready, of course ).
Do we have an emoji for "gets wallet out"?
Hang on, you've had this going since March 4? And I'm just hearing about it now?!?!?!
Sounds killer, I'm definitely in 8)
Quote from: bluebunny on March 20, 2018, 03:49:53 AM
Do we have an emoji for "gets wallet out"?
Quote from: vigilante397 on March 20, 2018, 10:32:47 AM
Hang on, you've had this going since March 4? And I'm just hearing about it now?!?!?!
Sounds killer, I'm definitely in 8)
:icon_mrgreen:
Yeah Man, I'd be into this project as well. It's pretty Juicy. Effects loop?
Ok, I've got a question for you all: How to do the panel layout?
Currently it has four knobs (Frequency, LFO rate, LFO depth, LFO waveform) and two switches (LP/BP/HP and Hi/Mid/Lo Resonance).
Does it need a volume/output level control too? How would you arrange 5 pots and two switches on a 1590BB enclosure? Do people expect enough room for their fingers around the knobs?
Personally I tend to favour big knobs and widely spaced and I try to keep things simple to accommodate this (not always successfully), but I see some fiddly designs out there where people have stuffed as many Davis 1900 clone knobs (about the narrowest that's available?) onto the panel as they can. And I'm not talking about the 1590A pictures thread either...;)
Your thoughts are welcomed!
Thanks,
Tom
Quote from: bluebunny on March 20, 2018, 03:49:53 AM
Do we have an emoji for "gets wallet out"?
Sticker enough? get this money :icon_mrgreen:
(https://sdl-stickershop.line.naver.jp/products/0/0/1/1373568/android/stickers/14666240.png)
Quote from: ElectricDruid on March 20, 2018, 11:09:54 AM
Ok, I've got a question for you all: How to do the panel layout?
Currently it has four knobs (Frequency, LFO rate, LFO depth, LFO waveform) and two switches (LP/BP/HP and Hi/Mid/Lo Resonance).
Does it need a volume/output level control too? How would you arrange 5 pots and two switches on a 1590BB enclosure? Do people expect enough room for their fingers around the knobs?
Personally I tend to favour big knobs and widely spaced and I try to keep things simple to accommodate this (not always successfully), but I see some fiddly designs out there where people have stuffed as many Davis 1900 clone knobs (about the narrowest that's available?) onto the panel as they can. And I'm not talking about the 1590A pictures thread either...;)
Your thoughts are welcomed!
Thanks,
Tom
1590BB?
5 pots inline. and the 2 switch is below the 2 & 4 pots. Symmetry?
(https://1.bp.blogspot.com/-hWWWSg6NIbE/WrEpfT1LElI/AAAAAAAAAt4/KMudsywFv_MM6p32yK657uc0qCLuNg9IACLcBGAs/s1600/1590bb.png)
Leave off the volume, keep it at 4 pots/2 switches and I want it in a 1590B :icon_mrgreen:
Quote from: 287m on March 20, 2018, 11:33:31 AM
1590BB?
5 pots inline. and the 2 switch is below the 2 & 4 pots. Symmetry?
(https://1.bp.blogspot.com/-hWWWSg6NIbE/WrEpfT1LElI/AAAAAAAAAt4/KMudsywFv_MM6p32yK657uc0qCLuNg9IACLcBGAs/s1600/1590bb.png)
Nice, that could work. What's the spacing on those pots? They look pretty tight to me. Oh, and I forgot to mention it has a tap tempo foot switch as well as the 3PDT...still, we've got lots of room at the bottom, so no problem there.
T.
Quote from: vigilante397 on March 20, 2018, 11:39:17 AM
Leave off the volume, keep it at 4 pots/2 switches and I want it in a 1590B :icon_mrgreen:
Yeah, that'd be nice. Don't know what you'd do about the tap tempo foot switch though. Can you put two foot switches on a 1590B? I suppose horizontally it would work...hummm...
T.
Quote from: ElectricDruid on March 20, 2018, 11:48:27 AM
Can you put two foot switches on a 1590B?
I have before, but only once. I smash my footswitches as far as I can to the bottom of the box, then I just had one in each corner. Maybe not the best option. 1590BB is fine then I suppose :P
Very nice.
If you want to be able to tweak the input gain, you could always do this with a switch that also pads down the volume so you add a switch instead of a pot. Not sure that helps much.
Which PIC did you settle on?
If there are to be two stompswitches, then the toggles need to go between (in the space just below), controls 2&3, and 3&4, such that there is maximum distance between the user's steel-toe work-booted size 13 foot and the toggles.
The proposed volume pot should probably be able to dial in a level somewhat below bypass, and somewhat above, such that the user can engage the pedal for rhythm OR solos. Keep in mind that upping the resonance also increases the output level. So if a user wants to bring in sweeps for rhythm work, they want to be able to avoid surprising shrieks.
Not to beat the horse mercilessly, but my own experience and view is that downward sweeps often have to start a bit lower, and not simply replicate the min/max sweep points of an upward sweep. That obviously bears no relevance for some of the modulation patterns the chip is providing. But it likely does have some relevance to the sawtooth waveform which, even though repetitive, IS fundamentally a downward sweep.
(https://s14.postimg.org/57jso89wt/fry.gif) (https://postimg.org/image/57jso89wt/)
8)
Quote from: Mark Hammer on March 20, 2018, 12:12:40 PM
If there are to be two stompswitches, then the toggles need to go between (in the space just below), controls 2&3, and 3&4, such that there is maximum distance between the user's steel-toe work-booted size 13 foot and the toggles.
The proposed volume pot should probably be able to dial in a level somewhat below bypass, and somewhat above, such that the user can engage the pedal for rhythm OR solos. Keep in mind that upping the resonance also increases the output level. So if a user wants to bring in sweeps for rhythm work, they want to be able to avoid surprising shrieks.
Not to beat the horse mercilessly, but my own experience and view is that downward sweeps often have to start a bit lower, and not simply replicate the min/max sweep points of an upward sweep. That obviously bears no relevance for some of the modulation patterns the chip is providing. But it likely does have some relevance to the sawtooth waveform which, even though repetitive, IS fundamentally a downward sweep.
All good points, Mark.
I agree about the different sweep ranges. You finish up adjusting both the base Frequency and the LFO Depth when you change the waveform. Different shapes need different settings.
Tom
I can look at doing a tremolo with the chip Tom.
I'll start a new thread when I've had a play with it on the breadboard.
I have a thing on the breadboard with Tom's LFO 8pin chip and let me say it's a breeze to implement and the only LFO i've made that compares was a complicated mess that took up so much real estate i scrapped it. Highly recommended!
Quote from: garcho on March 20, 2018, 01:30:37 PM
I have a thing on the breadboard with Tom's LFO 8pin chip and let me say it's a breeze to implement
Jelous here.
Quote from: samhay on March 20, 2018, 12:02:34 PM
Which PIC did you settle on?
It's a 16F18313 in the end, one of the recent enhanced midrange chips.
Code and details are online here if you're curious:
https://electricdruid.net/electric-druid-chips-the-next-generation/ (https://electricdruid.net/electric-druid-chips-the-next-generation/)
Thanks for the link (and for sharing the code, even if it is in assembly).
That looks like a very useful little chip. Will have to add some of these to the next Farnel order.
PDM is a nice feature - I guess it would be much easier to get this to drive something other than an LED (like a JFET).
Quote from: EBK on March 19, 2018, 06:37:14 PM
Thought for a sec that the second knob was labeled "Druid Rate", which had me stumped. Shows that I need to read all of the labeling before trying to figure out what each knob does. :icon_lol:
Makes sense to me: "Druid Rate", "Filter Depth", "FX Wave".
.sig goes here.
In suggesting a output volume pot, I mean - does it sound like it needs one, when listening to the amp (as opposed to phone)?
Quote from: blackieNYC on March 21, 2018, 12:37:18 AM
In suggesting a output volume pot, I mean - does it sound like it needs one, when listening to the amp (as opposed to phone)?
I dunno to be honest. The prototype has no bypass switch, so it's hard to tell. More experiments needed before a final decision can be made there, I think.
T.
Quote from: blackieNYC on March 21, 2018, 12:37:18 AM
In suggesting a output volume pot, I mean - does it sound like it needs one, when listening to the amp (as opposed to phone)?
Much like tremolo, when you take away portions of the signal, via filtering, or by arriving at a lower average overall level, it's helpful to be able to balance bypass-vs-effect level.
^ but unlike tremelo, filters have resonance. i would throw a super simple compressor in there (opto, NE57x etc), no need for compressor controls, just auto-squish the pointy peaks. of course, that means a bigger PCB...
omfg - almost forgot about those beauties! Ordered a couple :)
Ok, I've got a Rev.1 (definitely "prototype") PCB layout done for this:
(https://electricdruid.net/wp-content/uploads/2018/03/BoardRev1LoResTop.jpg)
(https://electricdruid.net/wp-content/uploads/2018/03/BoardRev1LoResBottom.jpg)
As it says, I need to check the switch footprint before I pull the lever on this, but once the switches arrive, I'll get a few prototype boards made up and see how it looks and make any tweaks necessary. Usually there's a couple of small things, but I'm not envisaging anything major.
This Rev.1 includes components for the optional sync input for the LFO and also a location to add an expression pedal input (that's what the cut-out on the right is - gives room for the extra jack).
More soon..ish,
Tom
I see that Godlyke/TWA has adapted your TAPLFO chip for an expression-pedal input source.
http://www.effectsdatabase.com/model/twa/sidestep
(http://files.effectsdatabase.com/gear/thumbs/twa_sidestep_001.jpg)
ED - I have one on the breadboard. What is the "onset - base frequency before modulation"?
My HP and BP outputs are working, but the LP isn't doing anything that I can hear. Passes audio.
On the breadboard, there is a lot of LFO noise in the audio output - did anyone experience this on the breadboard? I ave filter caps in place.
Quote from: blackieNYC on May 02, 2018, 08:14:56 PM
ED - I have one on the breadboard. What is the "onset - base frequency before modulation"?
It sets the "bias level" if you like. Imagine you turn the depth down to zero - what level do you get? That controls sets that level. As you turn the depth up and up, it becomes a moot point since at max depth the output is 0-5V whatever you do.
On the FilterFX specifically, if you turn the depth down, you can use the offset control to manually sweep the filter over the full range - add an expression pedal for wahwah. Or you can have a limited depth and just filter the treble or just the bass or whatever.
Quote
My HP and BP outputs are working, but the LP isn't doing anything that I can hear. Passes audio.
That's pretty weird for a SVF, since all the outputs interact, pretty much. I'd check you've got the feedback paths correct - those are easy to get wrong; R6 and R7. Note they *don't* go back to the same place. IC1.2 is a differential mixer not a simple mixer.
Beyond that..dunno - a problem with the integrator caps C2 and C3 maybe? They're pretty critical too.
Quote
On the breadboard, there is a lot of LFO noise in the audio output - did anyone experience this on the breadboard? I ave filter caps in place.
What does the LFO noise sound like? Actual LFO feedthrough would be ultrasonic, so you won't hear that, but you might get some ticks or bumps or something. But I'd get the filter working first and then see what the situation is. I have a feeling this might fix itself.
HTH,
Tom
It cleared up somehow. I must have had a short on the breadboard in that last op amp stage.
The Depth and the Offset both seem to have all the action at one end of the pot. Particularly the Offset. I'll try a log pot, or maybe a series resistor.
The Sweep LFO setting - I can't tell - what is that supposed to do?
Quote from: blackieNYC on May 07, 2018, 10:15:46 PM
It cleared up somehow. I must have had a short on the breadboard in that last op amp stage.
Remember to give thanks to the Gods of the Breadboard for your blessings, or your circuits will remain ever faulty. ;)
Quote
The Depth and the Offset both seem to have all the action at one end of the pot. Particularly the Offset. I'll try a log pot, or maybe a series resistor.
Could it be that the optos aren't acting very linear? The controls for Depth and Offset are supposed to be linear pots, and they have a linear action. The pulse-density drive of the LED should give a pretty linear conversion to LED brightness too.
Quote
The Sweep LFO setting - I can't tell - what is that supposed to do?
It's a "hypertriangular sweep" - in this case approximated with the bottom of a sine wave (which is actually how it's done in some of the analog implementations I've seen). There's a picture in the datasheet:
https://electricdruid.net/datasheets/STOMPLFODatasheet.pdf (https://electricdruid.net/datasheets/STOMPLFODatasheet.pdf)
Depth pot is fine, but I really think all the action of the Offset pot is within the first 1 volt of the 5.
But it is really great! I must box this.
If you're offset is not effective (working) you can always tie pin2 to +5 or Gnd with a series 10k.
I'd check it with the scope.
Are you getting good voltages on the offset pot ?
Yes, I'm getting voltages but all the action seems to be under one volt. It continues up to 5v but it seems to be all highs from one volt up. Just seems like an A-Log pot covers the range a little better. Not a big deal.
Have you worked out how the Offset and Depth interact?
If you've got the depth turned up (say to 75%) then the offset will only have 25% of the range to work with, so it might look like only part of the range does anything.
If you turn the Depth down to 0%, you should be able to see the full range of the Offset. With Depth at 0%, the Offset CV allows you to sweep the output voltage over the whole range of the LFO, 0-5V.
I get the interaction now. I guess it's only with the depth set very shallow that the offset is more useful with a fraction of a volt on pin 2. Like in the setting you mentioned - with the depth pot at 0%, the guts of the manual sweep are in a small area of the offset pot. I might want to go with a log pot, but either way, it's good.
Hi guys,
i'm having trouble with my FilterFX,
i'm having loud clicks when switching 3PDT and the resonance & filter switches
Do you have same clicks on yours, or is it quiet?
Quote from: blackieNYC on May 09, 2018, 10:09:41 PM
I get the interaction now. I guess it's only with the depth set very shallow that the offset is more useful with a fraction of a volt on pin 2. Like in the setting you mentioned - with the depth pot at 0%, the guts of the manual sweep are in a small area of the offset pot. I might want to go with a log pot, but either way, it's good.
That's pretty much how the "Manual" and "Depth" controls work on a number of Boss pedals. The Depth pot essentially pans between the LFO and a DC voltage. More of one equals less of the other. It's done like that precisely to avoid one or the other exceeding a controlling DC beyond the capability of whatever it's modulating.
Quotei'm having loud clicks when switching 3PDT and the resonance & filter switches
Most probably 2 different issues. Without providing us with any other information, it will be difficult to figure out.
3PDT true-bypass with LED indicator is a never-ending source of troubleshooting around here. There are tomes written about it online, have you looked those over? First things first: do you have pull down resistors for your input/output caps? They're listed as R2 and R13 on Tom's schematic. Are you following the schematic exactly? Are you using one of Tom's boards?
Look over the "troubleshooting sticky" here (https://www.diystompboxes.com/smfforum/index.php?topic=29816.0) if you want anyone to really be able to help you.
thank you for your answer.
i checked the pulldown resistors R2 and R13 (2M2 and 100K), it's fine.
I'm building with Tom's board.
Loud Clicks (boosted by the resonance circuit) are happening when using the 3PDT, but happens too when the pedal is already on, using the switchs (resonance and filter type LP/BP/HP) or hitting (gently) the case with a piece of metal. Otherwise, the effect works fine.
I made no mod on the circuit, using the documentation.
(https://i.postimg.cc/jLfZnT1G/Filter-FXSchematic-Pg1.jpg) (https://postimg.cc/jLfZnT1G)
(https://i.postimg.cc/BLwMHn4G/Filter-FXSchematic-Pg2.jpg) (https://postimg.cc/BLwMHn4G)
Voltages :
STOMP LFO IC :
1 - 5.05
2- 2.43
3- 2.40 ( oscillating)
4- 4.93
5- 0
6- 3.80
7- 1.90
8- 2.90
IC1
1- 3.79
2- 3.79
3- 3.70
4- 0
5- 1.37 (??)
6- 3.79
7- 3.79
8- 7.50/7.60 (oscillating)
IC2
1- 3.79
2- 3.79
3- 3.79
4- 0
5- 3.79
6- 3.79
7- 3.79
8- 7.50/7.59 (oscillating)
TR1
C 2.3/2.5 (oscillating)
B 2.2/2.6 (oscillating)
E 5v
REG
C 5
B 0
E 7.5/7.7 (oscillating)
(https://i.postimg.cc/hJp3SqyN/IMG-20200605-185146.jpg) (https://postimg.cc/hJp3SqyN)
(https://i.postimg.cc/2by9yXgy/IMG-20200605-190844.jpg) (https://postimg.cc/2by9yXgy)
i've tried to resolder the switchs pins and checked the solder joints, without any success, i know it looks like a solder joint problem but i can't find it.
Do you think it can be a switch default, caused by an overheating?
Quote5- 1.37 (??)
As you noted, that looks incorrect. It's also the op amp pin directly connected to the input coupling cap, which might have something to do with the pop.
Quotehappens too when ... hitting (gently) the case with a piece of metal.
Check all your grounds, and anything touching your enclosure. Definitely a clue lurking there.
QuoteDo you think it can be a switch default, caused by an overheating?
I'm not sure exactly what your mean, but basically the only component that has a chance of over-heating in this circuit is the linear voltage regulator, and that will either smoke or shut itself down before smoking and the LFO would stop working at that point. Does the LFO work?
I'm guessing there is a grounding issue.
Thanks for the analysis!
Quote from: garcho on August 18, 2020, 08:19:43 PM
Quote5- 1.37 (??)
As you noted, that looks incorrect. It's also the op amp pin directly connected to the input coupling cap, which might have something to do with the pop.
yep, something might be wrong on this part, i have no clue how to know what, but i'll try to inspect the coupling cap and the virtual ground sectors
Quotehappens too when ... hitting (gently) the case with a piece of metal.
Quote
Check all your grounds, and anything touching your enclosure. Definitely a clue lurking there.
how do i check the grounds? you mean solders and contacts or do i compare ground voltage with another power supply ground?
QuoteDo you think it can be a switch default, caused by an overheating?
Quote
I'm not sure exactly what your mean, but basically the only component that has a chance of over-heating in this circuit is the linear voltage regulator, and that will either smoke or shut itself down before smoking and the LFO would stop working at that point. Does the LFO work?
I'm guessing there is a grounding issue.
i was thinking about melting plastic parts in the switchs, but i might be wrong.
The LFO works perfectly, and if the effect does too, as long as i dont touch switches and having pops.
i'm sorry for my lack of knowledge and experience, i'm learning, thank you for your patience! :icon_redface:
Quote from: garcho on August 18, 2020, 08:19:43 PM
Quote5- 1.37 (??)
As you noted, that looks incorrect. It's also the op amp pin directly connected to the input coupling cap, which might have something to do with the pop.
Quotehappens too when ... hitting (gently) the case with a piece of metal.
Check all your grounds, and anything touching your enclosure. Definitely a clue lurking there.
I agree with both of these points. That pin 5 shouldn't be at that voltage, so that needs to be fixed, and the fact that you can hear something when you tap the case is definitely a clue to something - that's not right.
thanks guyz, i'll find the source and let you know
for those interested, tom shared this interesting link about "pedal popping"
http://www.muzique.com/lab/pop.htm
Quote from: jackwithoneye on August 19, 2020, 02:50:45 PM
thanks guyz, i'll find the source and let you know
for those interested, tom shared this interesting link about "pedal popping"
http://www.muzique.com/lab/pop.htm
When you contacted me, I hadn't seen this thread and I thought that was all that was going on, but the rest of the symptoms you've described above make me pretty sure that's not it - this is not a basic case of pedal popping. Something else is happening, and if you find it, you'll probably find all the noise goes away.
> pin 5 shouldn't be at that voltage
Meter loading? There's no reason pin 7 would lay at 3.79V by accident. It could be following pin 5. But pin 5 is biased with a 2.2Meg resistor. If we have a 1Meg meter, pin 5 falls to a third(*) of its actual rest voltage while the meter is poking it.
(https://i.postimg.cc/642y4hh9/22-Meg1-Meg-42.gif) (https://postimg.cc/642y4hh9)
(*) Like 1/3.2. I can't make the numbers "come out right"; however I don't know the meter (datasheet or reality); and why half-supply seems to be 3.79V instead of 4.3V or so (weak battery?).
Quote from: PRR on August 19, 2020, 06:04:52 PM
> pin 5 shouldn't be at that voltage
Meter loading? There's no reason pin 7 would lay at 3.79V by accident. It could be following pin 5. But pin 5 is biased with a 2.2Meg resistor. If we have a 1Meg meter, pin 5 falls to a third(*) of its actual rest voltage while the meter is poking it.
(https://i.postimg.cc/642y4hh9/22-Meg1-Meg-42.gif) (https://postimg.cc/642y4hh9)
(*) Like 1/3.2. I can't make the numbers "come out right"; however I don't know the meter (datasheet or reality); and why half-supply seems to be 3.79V instead of 4.3V or so (weak battery?).
English is not my native language, i may have misunderstand some parts of your post , sorry for this
my Vbios voltage is 3.86v (measured between R20 and R21) not 4.5v. (device powered by a Ciocks dc7 power supply, it was 3.79v with a random testing power supply). The ciocks delivers 9.26v(600mA), the random one gives 9v
pin5 is about 1.20v ( i may have been wrong with the 1.37v, or it changed...)
VDD about 7.6v (REG1 in)
The R23 (47R) might overdrained voltage because it is a 47.9ohms, i can change it to 47-ish, but it still doesnt explain the difference, right?
As my meter doesn't go further 2M ohms, i dont get any conductivity and measure, but the R3 value is 2.2M ohms (red-red-green-yellow-brown).
i'll get a high end meter, i promise.
What is your source of power? Why is it 7.5 volts? It doesn't explain the issue you have, but it could be another clue. Battery? AC to DC wall adapter?
> What is your source of power? Why is it 7.5 volts?
He says "Vbios voltage is 3.86v (measured between R20 and R21) not 4.5v. ...Ciocks dc7 power supply,.... 9.26v(600mA), the random one gives 9v..."
Half of 9V should be more than 3.86V. Is one of the "4.7k" resistors not 4.7k? Or is something loading the Vref point?
Quote from: PRR on August 19, 2020, 09:27:27 PM
> What is your source of power? Why is it 7.5 volts?
He says "Vbios voltage is 3.86v (measured between R20 and R21) not 4.5v. ...Ciocks dc7 power supply,.... 9.26v(600mA), the random one gives 9v..."
Half of 9V should be more than 3.86V. Is one of the "4.7k" resistors not 4.7k? Or is something loading the Vref point?
R20 and R21 are both 4.7K, 4.64K to be precise.
the Vref point is loaded with R23, a 47R right?
on R23 : 1.29v
on D1 :0.28V
make sense?
(https://i.postimg.cc/mPwW1JxC/2020-08-20-03h58-46.jpg) (https://postimg.cc/mPwW1JxC)
(https://i.postimg.cc/xNHPJwZ2/2020-08-20-03h58-55.jpg) (https://postimg.cc/xNHPJwZ2)
(https://i.postimg.cc/w3hJNQvg/2020-08-20-04h02-58.jpg) (https://postimg.cc/w3hJNQvg)
Taking a few voltages from the working unit on my workbench, the 7.6V seems to be about right. Running my pedal at 9.2V, I get a 1.2V drop across R23 (I used a 68R because I didn't have any 47Rs, so my situation is a bit worse). The pedal draws a fair bit of current (~25mA or so). This is perhaps not surprising with two optocouplers and two LEDs.
Consequently, with Vdd at about 7.8V, Vbias comes in around 3.8V. What's not right is that pin 5 voltage, which should be a lot closer to Vbias than 1.2V. Check the soldering on R3 and pin 5.
Incidentally, I now think I was being a bit exaggerated with the 2M2 values for R2 and R3. Other pedals I've done use 1M in those positions. I'm not entirely sure why I decided this needed a higher value. I was trying it out, I suppose. Anyway, it should work either way - 1M or 2M2.
Quote from: ElectricDruid on August 20, 2020, 09:02:59 AM
Taking a few voltages from the working unit on my workbench, the 7.6V seems to be about right. Running my pedal at 9.2V, I get a 1.2V drop across R23 (I used a 68R because I didn't have any 47Rs, so my situation is a bit worse). The pedal draws a fair bit of current (~25mA or so). This is perhaps not surprising with two optocouplers and two LEDs.
Consequently, with Vdd at about 7.8V, Vbias comes in around 3.8V. What's not right is that pin 5 voltage, which should be a lot closer to Vbias than 1.2V. Check the soldering on R3 and pin 5.
Incidentally, I now think I was being a bit exaggerated with the 2M2 values for R2 and R3. Other pedals I've done use 1M in those positions. I'm not entirely sure why I decided this needed a higher value. I was trying it out, I suppose. Anyway, it should work either way - 1M or 2M2.
i switched R2 and R3 to 1M resistors an checked pin 5 soldering, it gives me 1.9V on pin5.
Quote from: jackwithoneye on August 20, 2020, 11:05:39 AM
i switched R2 and R3 to 1M resistors an checked pin 5 soldering, it gives me 1.9V on pin5.
That's still odd. You've still got 3.8V or so for the Vbias, right? So at one end of that R3 resistor we've got the voltage we expect, and at the other end, we've got a voltage which is significantly wrong.
Could C1 be shorted/a bad cap? That mean R2/R3 connect the Vbias to ground, effectively connected in parallel with R21/4K7. Since their values are so large in comparison with R21, you wouldn't see much effect on the Vbias itself. But the other effect would be that pin 5 would be connected to the middle of a R2/R3 voltage divider, so it would see half the usual Vbias level - probably about 1.9V for a 3.8V Vbias. That fits with what we're seeing.
A shorted cap would also explain why you get hideous pops and thumps when you switch the pedal. There'd be no DC blocking, so the input has a hefty DC voltage on it.
Try replacing C1/100n with a new cap, unless there's a bit of solder or something shorting its connections that you can fix.
Quote from: ElectricDruid on August 20, 2020, 12:36:13 PM
Quote from: jackwithoneye on August 20, 2020, 11:05:39 AM
i switched R2 and R3 to 1M resistors an checked pin 5 soldering, it gives me 1.9V on pin5.
That's still odd. You've still got 3.8V or so for the Vbias, right? So at one end of that R3 resistor we've got the voltage we expect, and at the other end, we've got a voltage which is significantly wrong.
Could C1 be shorted/a bad cap? That mean R2/R3 connect the Vbias to ground, effectively connected in parallel with R21/4K7. Since their values are so large in comparison with R21, you wouldn't see much effect on the Vbias itself. But the other effect would be that pin 5 would be connected to the middle of a R2/R3 voltage divider, so it would see half the usual Vbias level - probably about 1.9V for a 3.8V Vbias. That fits with what we're seeing.
A shorted cap would also explain why you get hideous pops and thumps when you switch the pedal. There'd be no DC blocking, so the input has a hefty DC voltage on it.
Try replacing C1/100n with a new cap, unless there's a bit of solder or something shorting its connections that you can fix.
i switch the C1 with a new cap. Same results.
Dumb question time : , what is the role of R3 (was 2.2M, and now 1M)? If shorten it, won't i have the good voltage on IC1 pin5?
Quote from: jackwithoneye on August 20, 2020, 03:40:20 PM
i switch the C1 with a new cap. Same results.
Ah, dammit. I thought we were getting close!
Quote
Dumb question time : what is the role of R3 (was 2.2M, and now 1M)? If shorten it, won't i have the good voltage on IC1 pin5?
It provides the DC operating point for the op-amp - the "bias level". If you look at the schematic, no other pins have a defined DC level. The other input and the output are just connected together, without it being at all clear what DC level they are at. It could be anything, depending what the op-amp does. The +ve input is therefore crucial. It has its input held at the Vbias level by R3, and then the incoming signal is superimposed on that through C1.
Reducing the value of R3 further just reduces the input impedance. It shouldn't really do anything to the voltage.
Of course, that's a "it shouldn't - according to theory", so if you want to try it go ahead (stick a 100K in there instead) and see what happens, you never know, we might learn something interesting. I think it's a long shot though, to be honest.
thank you for the explaination, it's overpass my competences, but that's interestinng to understand.
i put a 100K in parallel of the 1M R3 (which gives 90K approx)
result : pin5 at 3.5V
Ok, I'll have to think about what that means!
Does it help with the thumping when you switch it? After all, that's what we're really trying to fix.
Quote from: ElectricDruid on August 20, 2020, 07:26:36 PM
Ok, I'll have to think about what that means!
Does it help with the thumping when you switch it? After all, that's what we're really trying to fix.
no, it doesn't unfortunately.
And having more voltage on IC1 pin5 doesn't really affect the effect. It's still good, not better, not worse.
If you weren't slamming it with an amped up signal, maybe you were never hitting the power supply limits and distorting the audio, so it sounds the same now. It's still a good thing you got that voltage level where it should be, closer to V/2.
Are you certain that all grounds are connected, especially your input and output jacks? Are you certain there aren't intermittent shorts near any pots or switches? Try wiggling all the panel mount stuff, knobs, switches, led bezel, DC jack, see if that makes any crackling. Do you get any crackling when adjusting the pots? Move all the knobs from one end to the other and listen for any crackling or static sound. Just fishing for clues.
What's your signal chain when testing this? Guitar => pedal => amp? Anything else in there?
The voltage at pin 5 going up when you reduce the size of that resistor still only makes sense to me if it's part of a voltage divider. Can you do a continuity test across C1 please? I know you've replaced it, so it's probably not the cap, but maybe there's a PCB fault or something.
wiggling parts doesn't generate pops (only when switching, especially when resonance is on, but it does it the filter selector swotch too) and i checked grounds.
signal path :
guitar->FilterFX->HXStomp->powered Monitoring speakers
and
guitar->FilterFX->'67 Deluxe Reverb Amp
i sometime use a looper instead of guitar to ease testing
continuity across C1 : around 1.1M
thanks again for the brainstorming guys :)
Question:
So, I'm subbing the Resonance Switch for a pot wired as a variable resistor, connected between the 10K minimum resonance to the stage 3 output. I now have a minimum resistance, 10K, but I'm confused... The problem is the 1M pot I'm using cuts off at the extremes. The 10k takes care of the min resistance. Now, for the max resistance... how do I hook this up? Since I'm using only lug 3 and the wiper o the pot, essentially.
I thought about connecting lug 1 to the 680k resonance resistor (and making it a smaller value, 330k or so) and the lug 3 to that 10k and then the wiper to the stage 3 output... that would just blend between the two, no?
Like I said, I'm confused :icon_mrgreen:
My layout:
(https://i.postimg.cc/Hj33pk6w/Layout-Electric-Druid-Filter-FX.png) (https://postimg.cc/Hj33pk6w)
Quote from: jackwithoneye on August 21, 2020, 08:37:33 AM
continuity across C1 : around 1.1M
thanks again for the brainstorming guys :)
does it make sense to you tom?
Quote from: strungout on August 24, 2020, 03:38:34 PM... :icon_mrgreen:
(https://i.postimg.cc/JGYKpm3K/strungout-680k-42.gif) (https://postimg.cc/JGYKpm3K)
Thanks, Paul! I didn't think of putting a resistor in parallel with the outer lugs. Basically, I was looking for a setting that will allow some distortion cause by the 'resonance', on top of having a clean sound. I'll play around with that 2M value :)
Quote from: jackwithoneye on August 24, 2020, 05:37:30 PM
Quote from: jackwithoneye on August 21, 2020, 08:37:33 AM
continuity across C1 : around 1.1M
thanks again for the brainstorming guys :)
does it make sense to you tom?
No, not much, if I'm honest. 1.1M is too big to be a short, but not really big enough to be just board resistance. I'm stumped. There shouldn't be *any* continuity across C1 - hence my request for the test.
Quote from: ElectricDruid on August 25, 2020, 06:07:54 AM
No, not much, if I'm honest. 1.1M is too big to be a short, but not really big enough to be just board resistance. I'm stumped. There shouldn't be *any* continuity across C1 - hence my request for the test.
excuse my french, i still haven't finsihed my "electonic for dummies" book but basically, measure conductivity over C1 gives the conductivity over the virtual ground (R2+R3+R21 through ground and vBios)? Am i wrong?
(https://i.postimg.cc/RNm7Zq1X/2020-08-25-23h39-05.jpg) (https://postimg.cc/RNm7Zq1X)
Quote from: jackwithoneye on August 25, 2020, 05:39:45 PM
excuse my french, i still haven't finsihed my "electonic for dummies" book but basically, measure conductivity over C1 gives the conductivity over the virtual ground (R2+R3+R21 through ground and vBios)? Am i wrong?
(https://i.postimg.cc/RNm7Zq1X/2020-08-25-23h39-05.jpg) (https://postimg.cc/RNm7Zq1X)
No, you're not. Well spotted. So "around 1.1M" is *exactly* what you'd expect to see.
That's a good thing, at least!
Just bumping this thread to say that this is a very cool pedal! I ordered a board last year and finally got around to building and boxing it this week. Worked great on first go, lovely build instructions and documentation. Only spent a few minutes with it sweeping the pots but it did everything one would expect.
Just curious - what are the hi/med/lo resonance settings fixed at?
(https://i.imgur.com/dsVnbB7.jpg)
Quote from: mdcmdcmdc on December 09, 2021, 10:35:35 PM
Just bumping this thread to say that this is a very cool pedal! I ordered a board last year and finally got around to building and boxing it this week. Worked great on first go, lovely build instructions and documentation. Only spent a few minutes with it sweeping the pots but it did everything one would expect.
Just curious - what are the hi/med/lo resonance settings fixed at?
(https://i.imgur.com/dsVnbB7.jpg)
Errrm...they're fixed at high, medium, and low resonance?!? Lol!
I have no idea what actual Q settings they give, I'm afraid. They just go from "less" to "more". More helpfully, the resonance switch picks one of three resistors for the resonance feedback. The schematic sets those as 10K, 100K and 680K:
https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg1.jpg (https://electricdruid.net/wp-content/uploads/2018/03/FilterFXSchematicPg1.jpg)
When I was experimenting with the prototype, I found that exponential changes gave a better jump in resonance. Also note that *bigger* values give *more* resonance. This happens because the resistor actually sets the damping in the circuit. It's set up so that it should oscillate (or close to it) with no resistor in place. Adding more damping (=lower value) reduces that resonance.
My first try was 10K, 100K, 1M, but I found the "high res" 1M setting was too thin and whistley and not that great, so I backed it off a bit to 680K. Of course, your taste may differ, and I always intended that people should experiment with these three resistor values which is why I laid them out in a row on the PCB with a little box around them so people could see what to play with. I recommend wiring a 1M log pot in one of the positions and trying out different settings. You can then choose three settings that suit your style and put those in as fixed resistors. Or if you can find space, wire the pot and leave the switch out.
Honestly though, I agree with Mark Hammer that actually for some settings, two, three, or maybe four (tops!) options is enough, which is why I went with a switch for this option. I don't really believe that Resonance is important enough to need endless tweaking. It's better to have three useful settings than an infinite number of ones that don't differ much. But I *do* totally accept that not everyone's three options need to be the same, so I would want people to tweak that to get the kind of range they're likely to use.
PS: Nice build, btw. I like the minimal panel. Glad to hear you're enjoying the pedal.
Hi guys!
Sorry for warming up this thread!
I just had a serious glance on the FilterFX project since it comes very close to my "ideal filter pedal" on the board of my dreams. Since it's Sync-Jack, the pedal could easily be tapped globaly by my Disaster Area Micro Clock. This is very nice!
One problem remaining:
Would it be possible for Electric Druid or any other human being to "update" the FilterFX PCB for usage with the TapLFO3 instead of the StompLFO?
Keeping all functions of the original FilterFX and adding the Tap Division (and the other waveforms) of the TapLFO3 would be a real dream in terms of a peal build for me.
Could anyone do this?
I personally haven't got the electronic knowledge to plan this, since I'm used to rebuild projects with at least documentation and pcbs. So sorry for that question coming from a noobie.
Cheers!
Albo
It's certainly possible. The TAPLFO would easily drop in to the circuit and could drive the filter in exactly the same way. The biggest problem would be panel space for all the potential options/pots.
Later note: I've changed my mind. I remembered that one of the significant differences between the two chips is that the TAPLFO doesn't have the Offset CV control (which is used to set the base filter frequency in the FilterFX pedal). That's a pretty big limitation. In some ways the StompLFO is the ideal chip for the job. The TAPLFO does have the BIPOLAR pin which selects between a 0V offset and a 2.5V offset, but you only get those two options, not a full pot to sweep from 0-5V like on the StompLFO.
So it's possible, but you'd have to find another way to control the basic frequency.
I don't think I've got time currently though, so sorry. If anyone else would like to have a go...?