I was busy trying to finish a 4049-based pedal I'd like to try and give to David Lindley this weekend when he comes to town (assuming I can bump into him at the festival). I've liked him for over 30 years and wanted to say thank you. In any event, I wanted to insert a simple variable lowpass filter treble-cut control and was just about to wire up a toggle with two different passive 2-pole filter settings when something ridiculously simple occurred to me. Simple enough that I'm sure it must be used somewhere (though I can't remember where).
Here's the deal. I had wanted to use a two-stage RC lowpass filter just ahead of the output volume control. Simple enough: two series resistors just ahead of the volume pot, and a small-value cap to ground after each series resistor. Of course, if you ignore the caps for the moment, the series resistors make the volume pot behave as if it is a higher value pot "turned down", so I was going to need to figure out how to compensate for the volume drop/difference in setting A vs B.
Then it hit me. I took a 10k linear pot and soldered a .018uf cap from the wiper to ground. The "output" of this pot went to the input of the 50k volume pot. The cap and whatever pot resistance there was between the wiper and the "input" leg of the pot formed a variable lowpass filter. because the 10k remained a constant series resistance, regardless of where the filter was set, the interaction between volume and tone pot was made negligible. To make sure there was an identified maximum treble point, I stuck a 1k fixed resistor in series with the input lug of the tone pot. Fired it up and it works like a charm. In my instance, the corner frequency ranges from about 8.8khz down to about 800hz, giving a pleasing range of "roundness" to the tone.
Those familiar with the Proco RAT "filter" control will recognize that it is a similar type of single-pole variable lowpass filter where the resistance of an RC pair is varied. The thing is, the filter control and output level pot are isolated from each other by a FET buffer in the Rat. IF you want to keep things simple, and IF the circuit has sufficient output that you can afford to "shave off" a couple of db by inserting an extra resistance in series with the volume pot, this does what the Rat filter does and works great.
I'm at language school right now so I can't post a drawing, but I'll try and do it later tonight. In the meantime, I'm pleased with myself.
Mark,
"Making the gift of a pedal to an apreciated guitarist"
I also had that tought. Last year coming back from a show here
in québec (mont-tremblant blues festival).
That was the band INDIGENOUS. It's a 3 member
blues guitar oriented band. So i went there, enjoyed the
show, had myself photographed with MAto (the guitarist leader).
I even asked the roadie,after the show, to take my camera and shoot the
floor right where the pedals where laying. Back home i could study
his pedals arragements.
On the way home, remenbering the show i just
experienced, i told my wife that i wished i had one of my pedals
in hand for that show. I would have gave it to Mato with my email,
phone number and ask him some comments on it.
What a great reward it would be to hear from a guitarist you like,
good comments on a design. ANd ultimatly see that he use live.
cbriere
That's a good idea, Mark. I used the rat tone control in an old shaka derivative but it affected the overall volume. (I didn't use the buffer to isolate it from the volume control.) If I understand correctly, you are attaching one end lug as an input and the other as output, keeping the max pot resistance in series. Then the wiper goes through the cap to ground. That should work really well- and it's simple. I like it! :D
Doug
That's great Mark, very simple and it works !! :D
Marty.
I think I follow that, but a picture would sure help. :oops:
Quote from: Doug_HThat's a good idea, Mark. I used the rat tone control in an old shaka derivative but it affected the overall volume. (I didn't use the buffer to isolate it from the volume control.) If I understand correctly, you are attaching one end lug as an input and the other as output, keeping the max pot resistance in series. Then the wiper goes through the cap to ground. That should work really well- and it's simple. I like it! :D
Doug
Thanks for the flattery, Doug, and yeah that's exactly how it works AND why I like it too.
But for one little bug that I hope to work out before the weekend, I like the way it sounds a lot. I used my version of the Anderton Tube Sound Fuzz (i.e., op-amp gain stage w/gain of 50, and attenuator before CMOS invertor stages), but stuck Anderton's midrange frequency booster ( http://www.muzique.com/schem/ca-eq.gif ) between the input gain stage and the 4049 invertor stages to get some nice "gronk" out of it. It is about as quick and dirty a version of a pedal with pre and post EQ as you can get but sounds nice and thick.
The nice thing about Anderton's frequency booster is that it can be made simple (on-off) or complex (multiple resonant frequencies, variable boost), and is defeatable with an SPST switch. That means you can implement a second stompswitch in a 1590BB chassis (which I did) to kick in the pre-boost for a different tone and get two different sounds from the same distortion. Simple and convenient and if you have an extra op-amp kicking around (e.g., you used 3 op-amps from a quad) well worth the few extra parts. BTW, the unit is usable with a +9v/4.5Vref supply. Those of you who have a taste for sticking fixed-position wahs ahead of an overdrive should take a peek at it. It won't do cut, only resonant boost (i.e., flat above and below boost zone), and while the resonant boost is not huge, it is quite noticeable, and just enough to push a distortion stage into frequency-specific rudeness. I used a 3-way toggle to select between .1uf and .027uf caps in series (boost around 940hz), .027uf only (boost around 740hz), and .1uf only (boost around 200hz). It might be more to my liking with the same arrangement but .033uf and .068uf caps instead. This would give boosts at around 900hz, 600hz, and just under 300hz, which makes for a better spread. That being said, it yields three easily distinguishable characters, plus a fourth if you cancel the boost. Big time ROI in my view.
Quote from: Paul MarossyI think I follow that, but a picture would sure help. :oops:
I second that emotion.
I *will* make a drawing later tonight, but for the moment imagine one capitol T standing up and another on its side just to the right slid right up against the first one. The one on the right is the output volume pot. The stem of the T standing up is a cap to ground.
what`s the little "bug" you mentioned?
QuoteI had wanted to use a two-stage RC lowpass filter just ahead of the output volume control
I thought you wanted 2 of them?
Did you use a dual ganged pot with each element in series for a total of 20K or????
Makes sense and it is simple.
Quote from: aronQuoteI had wanted to use a two-stage RC lowpass filter just ahead of the output volume control
I thought you wanted 2 of them?
Did you use a dual ganged pot with each element in series for a total of 20K or????
Makes sense and it is simple.
Yeah, if you wanted a 2 pole filter you would need 2 and a dual gang pot should work real well for that.
FWIW I just ran a sim of this and there's an obvious advantage to this over the rat style control where the pot is wired as a variable resistor. Esp with lower value volume pots, the db level with this control stays consistent whereas with the rat it varies all over the place. Of course it makes sense when you think about it but it's nice to see it printed on a graph. :D
If you can afford to eat a few db (and with most of these fuzzblasto circuits you easily can...) this is an elegant way of implementing a variable LPF tone control that maintains a consistent volume level.
Doug
Okay, I just posted it at http://hammer.ampage.org And just because it comes up now and then, a simple left click is confirmed to work fine.
Thanks for the diligent corroboration Doug. I'm pleased with my homebrew Rat clone, so the FET buffer obviously works well, but if you want to keep the parts count low, this works like a charm. I can easily see inserting it into a DOD250/YJM308/Dist+ clone, especially if one uses a 50k-100k volume pot.
Aron,
In a previous version of the same basic pedal (the green CMOS drive in the "family shot" at my site), I used a switchable 2-pole passive filter, and was going to do so here as well. It sounds great but when I realized I could easily implement a tunable filter without having to fart around with level balancing, I went with that. I still advocate use of 2-pole filters as a terrific sounding alternative, but went simple this time. And yes, you could use a dual ganged pot the same way, though the trick is to have the tone pot's value be relatively small in comparison to the volume pot's value.
Ton,
The "bug" was unrelated to the tone control. I realized on the way home tonight that I had foolishly stuck a DC-blocking cap between the input gain stage and the frequency booster stage, without having provided any means to rebias the frequency booster stage. As you can imagine, it tended to perform intermittently.
Oh, now I see. I totally misinterpreted that one. :shock: :oops:
Thanks for sharing that Mark. 8)
cc.: "bug": I had suspected s.th. similar... :)
I built the Tube Sound Fuzz years ago when it appeared in Guitar Player magazine. I never really appreciated it until giving it another listen recently. One problem I have is that it has so much gain that the volume pot can only be open a tad or the output is just way too much. Any thought on taming it a bit? This is the early schematic BTW. Maybe a prime candidate for your Tone Control, Mark.
thanks
log pot ("audio-taper")... ?
Quote from: RCZ53I built the Tube Sound Fuzz years ago when it appeared in Guitar Player magazine. I never really appreciated it until giving it another listen recently. One problem I have is that it has so much gain that the volume pot can only be open a tad or the output is just way too much. Any thought on taming it a bit? This is the early schematic BTW. Maybe a prime candidate for your Tone Control, Mark.
thanks
I tinkered with it and settled on something very close to this: http://www.geofex.com/FX_images/mhtsf.gif I like it a whole lot more than the original, though I wasn't aiming for any sort of serious fuzz.
Remove the 2-pole active lowpass on the right (from the 100k pot half all the way up to, but not including, the 10uf cap), and insert the SWTC between the 10uf cap and the output pot and you'll be home free. Personally I like to keep the potential volume so that I can set the drive low for just a little grit and still have enough output to overdrive an amp.
it's great Mark
i believe all the "tone miracles" are probably created by something like a crazy :idea: or accident and that's the cool little thing about it.
QuoteOne problem I have is that it has so much gain that the volume pot can only be open a tad or the output is just way too much.
Simple mods page:
http://www.diystompboxes.com/cnews/mods.html
That's slick as heck, Mark.
-Eric
You know you've done it when you leave everybody scratching their heads saying, "It's so simple, why didn't I think of this years ago?"
Thanks for enlightening us all. That's a beautiful work of genius and it may end up as a high end roll-off for a high gain LM386-based distortion I brewed up recently
Quote from: TransmogrifoxYou know you've done it when you leave everybody scratching their heads saying, "It's so simple, why didn't I think of this years ago?"
Yeah, I know... :D I keep thinking I
must have seen this somewhere before... Maybe it's in an amp or hifi circuit somewhere. :?: But it doesn't matter- even if it does exist in some form or fashion, it was a nice "voila" moment that Mark had on his own. And I'm glad he shared it with us. :D
Doug
Mark, that tone control is elegant! Here it is for anyone who cares to see it in schematic form.
100k 10k(tone)
___ ___
-----|___|-----|___|-----.
A |
| |
| .-.
--- | |<-----
0.018uF --- | | 50k(vol)
| '-'
| |
| |
=== ===
GND GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
EDIT: I see mark has a write up on it at his page. http://hammer.ampage.org/
Quote from: Jason StoutMark, that tone control is elegant! Here it is for anyone who cares to see it in schematic form.
100k 10k(tone)
___ ___
-----|___|-----|___|-----.
A |
| |
| .-.
--- | |<-----
0.018uF --- | | 50k(vol)
| '-'
| |
| |
=== ===
GND GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
This was my interpretation of Mark's original post, but the drawing Mark linked later on in the day looks different than this...
That's cool as heck, Mark. I may have to try this in my Sixteen Overdrive circuit. It doesn't have a tone control now and I didn't want a full 3 knob tone stack. This looks perfect.
now how about a switchable nF or half across the outer tonepot lugs?
(variable notch bridged-T).
Quote from: puretubenow how about a switchable nF or half across the outer tonepot lugs?
(variable notch bridged-T).
Well there you go! Proof positive that:
a) international cooperation is a good thing, and
b) two heads ARE better than one! :)
Okay, let's take it a step further. Let's leave one end of the bridging cap tied to the junction of the two pots, and send the other "free" end to the common of a 3-way SPDT toggle. The toggle now reroutes the free end to ground, to nowhere, OR to the other end of the tone pot.
This yields the original configuration of a variable lowpass, the tweakable bridged-T you wisely noted, plus a bizarre sort of 2-pole lowpass with a quirky sort of response. Note that when the tone pot is set at max resistance in this latter setting, the two caps now become parallel caps, increasing the combined capacitance and lowering the rolloff frequency.
Man, that's a whole lotta tonal possibility for a pot, two caps, and a toggle!
If a person wanted to get truly freaky, use the 3-way toggle as described, but have one of the side positions bridge the input and wiper of the volume pot for a treble bypass, and the other side position birdge the T as described. This could provide crude types of bandpass, notch and lowpass response. I like it!
where are the "simulator-guys" ?
Terrific stuff Mark, now I'm thinking of 2 optos to replace the tone pot, each driven by a LFO in opposite directions................
Stephen
http://diystompboxes.com/sboxforum/viewtopic.php?t=35068...
:wink:
Nice simple circuit! Will have to try it someday.
Hi Mark,
Quote from: Mark Hammer
I tinkered with it and settled on something very close to this: http://www.geofex.com/FX_images/mhtsf.gif I like it a whole lot more than the original, though I wasn't aiming for any sort of serious fuzz.
Remove the 2-pole active lowpass on the right (from the 100k pot half all the way up to, but not including, the 10uf cap), and insert the SWTC between the 10uf cap and the output pot and you'll be home free. Personally I like to keep the potential volume so that I can set the drive low for just a little grit and still have enough output to overdrive an amp.
I built a few CMOS circuits: Insanity, 3 legged dog, Frank Clark's Hot Harmonics and Double D. I really liked the Jiggle section of the Double D. It sounded quite Fender-ish.
Just wondering if you or others have tried integrating the CMOS section of your Tube Sound Fuzz into an amplifier emulation like Runoffgroove’s Professor Tweed? http://runoffgroove.com/professor.html
Basically replacing the op-amp in your TSF circuit with the 1st stage, volume control and tone circuit of the Professor Tweed circuit. Then use the CMOS section of your TSF circuit starting from 100K to the output of the 2nd CMOS section. Build an buffer like an emitter follower. Then take the output coupling cap 22n and the dual low pass filters of the Professor Tweed circuit. You could even replace the 1st low pass filter with your simply wonderful tone control.
I’m imagining it might sound pretty good. I would love to get the tone of a Fender Deluxe Reverb clean through cranked. I’m itching to try this but we are currently selling our house so I can’t mess it up with the circuits right now. My wife would kill me.
Regards,
Quote from: Mark Hammer
Thanks for the diligent corroboration Doug.
Not a problem, Mark. I've got something on the breadboard with a variable LPF. I'm going to try this approach and see how it compares.
Doug
QuoteI keep thinking I must have seen this somewhere before... Maybe it's in an amp or hifi circuit somewhere.
There is a Pultec passive EQ that uses this T-type configuration :D
regards, Jack
A-HA! I figured it was too damn simple to have never been thought of. Should I assume that said EQ has an LC combo going to ground instead of just a cap?
http://v3.espacenet.com/origdoc?CY=gb&LG=en&F=4&IDX=US3514723&DB=EPODOC&QPN=US3514723
?
I was just exchanging notes with Doug Hammond about this, and the idea occurred to me.
Imagine the following. Two inverting op-amps, both with diode pairs in the feedback loop, Ã la TS-9. Lets give the first one a gain of 40 or so, and the second a gain of maybe 20. That's 800 when multiplied, but the diode pair in the first stage will keep the signal amplitude form the first stage "under control". It will also fuzz up the signal and add treble content, which the 2nd clipping stage will now exaggerate even more. A gain of 20 in stage 2 isn't all that much but when you start out with a hefty signal, you reach clipping threshold more often.
Okay, bear in mind that the gain of an inverting op-amp is derived from the ratio of the feedback to input resistor. Now, let's make that input resistor the pot of our SWTC. So, a 10k pot in series with a 1k-1k8 fixed resistor goes to the "-" pin of the op-amp and we use a 220k feedback resistor. The wiper of the pot connects to ground through a cap. What we have is a between-stages tone control that varies the treble content of what gets transferred between clipping stages.
So far so good? Great, because here comes the spiffy part. We make that 10k pot one half of a dual-ganged pot, and stick the other half of the pot AFTER the second clipping stage. What we have here is a very simple pre-clip-post-clip EQ control in one knob that not only feeds the 2nd clipping stage more treble but also "shaves off" less of the treble post-clip, all the while having little impact on signal level because all that changes is essentially the "location" of the treble bleed cap along the pot's resistive strip, NOT the pot's resistance. Hot damn, I'm tickled with myself this morning! :lol:
Note that there is no reason why the treble-bleed caps have to be identical value, or why the adjustment range for each pot half HAS to be identical. On paper, anyways, this should provide a single tone control that can change the character of the distortion generated, not just the degree to which the treble is "tamed" post-clip.
Cool idea. I had thought about doing that with 2 BMP tone controls and a dual gang pot. Haven't gotten around to it so far. 8)
archive
David Lindley told GP long ago that he thought Simply Wonderful was a great stage name. His music is beautiful.
Quote from: Mark Hammer on July 13, 2005, 12:36:23 PM
Quote from: puretubenow how about a switchable nF or half across the outer tonepot lugs?
(variable notch bridged-T).
Well there you go! Proof positive that:
a) international cooperation is a good thing, and
b) two heads ARE better than one! :)
Okay, let's take it a step further. Let's leave one end of the bridging cap tied to the junction of the two pots, and send the other "free" end to the common of a 3-way SPDT toggle. The toggle now reroutes the free end to ground, to nowhere, OR to the other end of the tone pot.
This yields the original configuration of a variable lowpass, the tweakable bridged-T you wisely noted, plus a bizarre sort of 2-pole lowpass with a quirky sort of response. Note that when the tone pot is set at max resistance in this latter setting, the two caps now become parallel caps, increasing the combined capacitance and lowering the rolloff frequency.
Man, that's a whole lotta tonal possibility for a pot, two caps, and a toggle!
If a person wanted to get truly freaky, use the 3-way toggle as described, but have one of the side positions bridge the input and wiper of the volume pot for a treble bypass, and the other side position birdge the T as described. This could provide crude types of bandpass, notch and lowpass response. I like it!
Mark
Is this what you were getting at with this one?
Did you end up trying it (I know...it was a while back...)
(http://www.mrdwab.com/john/SWTC-diagram.jpg)
Thanks
John
After rereading the post of mine that prompted your drawing, yes that is exactly what I was suggesting. Have I ever tried it? No, but once you draw it out, it looks tempting.....
Ok, thanks for the confirmation Mark .
I was doing some archive digging and came across some other notch filter notes for the shin-Ei and Superfuzz with similar theories on this theme. I'll have to test these out.
Thanks!!
John
Saw this at the other forum from 1966 look at the tone control
https://www.freestompboxes.org/viewtopic.php?p=289322#p289322 (https://www.freestompboxes.org/viewtopic.php?p=289322#p289322)
Yup, not my idea at all. I just gave it a catchy name. I forget where I first saw it, but it made me think "Hey, I could do that too! That could be really useful."
Quote from: Gus on February 06, 2022, 08:57:19 AM
Saw this at the other forum from 1966 look at the tone control
https://www.....org/viewtopic.php?p=289322#p289322 (//https:///viewtopic.php?p=289322#p289322)
Posted 12 years ago: http://www.muzique.com/news/cheap-fuzz-again/
:icon_mrgreen: :icon_mrgreen:
Best regards, Jack
Excellent! Good catch, Jack! :icon_biggrin: :icon_biggrin:
Here is what LTSPICE said re the SWTC values chosen in the Wampler Ecstasy:
(https://i.postimg.cc/zqzdVrVW/Warped-Delight-Tone-Control.jpg) (https://i.postimg.cc/zqzdVrVW/Warped-Delight-Tone-Control.jpg)
quite a while ago i worked on a filter that switches from being a lowpass to a notch using a toggle, and a single pot determined the depth of both filters (depth, not frequency) the SWTC circuit reminds me of it. kind of the fuzz 1/2 switch on a super fuzz, but with variable depth. the scoop was at 500-ish Hz and the low pass was at 1500Hz, and they were tuned to deliver similar level drops so that switching over didn't change output volume.
it really needed to be driven by a low impedance source to keep the response the way i wanted it, but worked fantastically. ill look in to my note book if i can find its schematic, maybe even with values of the filters.
cheers
I'd like to see that, Iain...maybe something a little more fun than just 'the usual hi cut'! Maybe if used in conjunction with something else...bass cut etc.
Quote from: GibsonGM on February 08, 2022, 05:47:49 PM
I'd like to see that, Iain...maybe something a little more fun than just 'the usual hi cut'! Maybe if used in conjunction with something else...bass cut etc.
I originally planned to put a bass cut before the distortion circuit, and that switchblade tone stack behind it.
Right now im looking my notebook in my moving boxes, I think ill be back in like 15 minutes with pictures
Cheers
Quote from: iainpunk on February 09, 2022, 09:35:03 AM
Right now im looking my notebook in my moving boxes, I think ill be back in like 15 minutes with pictures
Cheers
So.... In the meantime, i accidentally burned dinner, had to get new meat and got distracted by starting over.
(https://i.postimg.cc/xcSZf5yz/IMG-20220209-233336-716.jpg) (https://postimg.cc/xcSZf5yz)
Here's two versions of the stack, i think i ended up using the top one, as its a bit more elegant.
Cheers