Harmonic Percolator 2nd Build Looking for New Ideas and Mods.

[replaceablehead]

I'm thinking of building a second Harmonic Peculator.

My current unit sounds pretty amazing. I really think this circuit does something drastically different and compelling. You can really hear this unique harmonic resonance, I don't know what it reminds me of... it almost sounds like a grainy reverb.

I'm not convinced on the whole even order harmonics thing, to me it does sound a little bit like an exploding Tweed Amp, but it also sounds like the cold clanging steel of a solid state distortion. If you ask me it's just creating a lot of harmonics which a reminiscent of both valve and solid state.

I feel like the circuit has huge untapped potential, but its got problems. As good as my current HP is it's unreasonably noisy I mean, holy honking fuzz vacuums batman this thing sounds like I'm in a wind tunnel before I even roll up the volume knob. It's also microphonic, which I don't hate, but it would be accurate to say that it's microphonic to the point of being an actual microphone.

The current transistors are a very leaky MP16A 50HFE GE and I think the silicon is a 2n5088, although I should probably double check.

There's a couple of things I want to add to the build.

First of all I'd like to add a diode pot like the one on the Karma Suture. I like the pedal with both the diodes engaged and diodes lifted and I have a suspicion I would like something in between even more. Anyone go any idea what the best way of wiring the pot for this would be? Do I just wire it in series between the diodes and ground?

Also I'm thinking of bread boarding some more extreme changes. Anyone got any suggestions on how to remove some of the noise other than a low pass filter, even if it means more drastic changes?

Lastly I have a dream of creating something like this that produces the same kind of harmonics, in more of an overdrive, with more acceptable noise. I like the way the pedal sounds with the volume down, but the signal to noise ratio becomes unacceptable.

So I was hoping people might have some mods they could share.

[replaceablehead]

Oh and another question I've been dying to know the answer to, whats with C4 in the pepperspray schematic? It's marked as either a 2.2uf, or 1uf and I don't see it in many other layouts.

http://www.madbeanpedals.com/projects/_folders/1590A/pdf/PepperSpray2018.pdf

[PRR]

> whats with C4 in the pepperspray schematic? It's marked as either a 2.2uf, or 1uf and I don't see it in many other layouts. http://www.madbeanpedals.com/projects/_folders/1590A/pdf/PepperSpray2018.pdf

Did you read the note bottom-left of that plan?

You need a cap here. One or few uFd, probably not too critical.

[replaceablehead]

Is that a quote from the file?

I must be blind, but I've done control F searches for "1uf" "2.2uf" "C4" etc and I can't find that anywhere in the pepper spray doc.

Do we know what it really does though?

[PRR]

It's in the *image*.

Does that help any?

[edvard]

For a "new idea", I took the silicon version and "flipped" it, just to be different and see if the circuit still worked.  It does, and it sounds a bit different.  Tweak to your satisfaction:



You can omit D1, that was just there to test an idea, and the output buffer is there to preserve some output gain, I think.  I can't remember...

[replaceablehead]

It's in the *image*.

Does that help any?

Ah now I get what everyones on about. Yeah I saw that. I'm not talking about using 1uf vs 2.2uf. I mean what does it do? I've seen other schematics with vastly different values for this cap and I guess I'm wondering what it does. I've seen people talk about the effects of changing pretty much all the other values.

My current HP is super microphonic. I realized that when I have it on the whole guitar seems to become microphonic... it's weird if I tap any metal part of the guitar you can hear it loud as day.

[replaceablehead]

For a "new idea", I took the silicon version and "flipped" it, just to be different and see if the circuit still worked.  It does, and it sounds a bit different.  Tweak to your satisfaction:



You can omit D1, that was just there to test an idea, and the output buffer is there to preserve some output gain, I think.  I can't remember...

Sounds awesome, I'm definitely going to try out the jerkulator as well.

What does it sound like? Is it more fuzzy, more overdrivey?

[PRR]

> what does it do?

Q1 is a simple amplifier. So is Q2. C4 couples Q1 output to Q2 input.

Q1 Q2 are "stacked". C3 supposedly keeps the AC/audio signals separate. Nominally this saves on current; one of the early patents was for telephone with a high-V low-I supply. In this low-V system with just ~~2V across 91k, 20uA current, it can't be about economy. (LED is fed far more than the amplifiers.) I suspect C3 does not really isolate the two amplifiers and something wacky happens.

[edvard]

For a "new idea", I took the silicon version and "flipped" it, just to be different and see if the circuit still worked.  It does, and it sounds a bit different.  Tweak to your satisfaction:

You can omit D1, that was just there to test an idea, and the output buffer is there to preserve some output gain, I think.  I can't remember...

Sounds awesome, I'm definitely going to try out the jerkulator as well.

What does it sound like? Is it more fuzzy, more overdrivey?

The sound is a bit strange to describe, because my ears probably use different adjectives than yours, but I'll make the attempt:
 
Overall, it has that same silicon 'splat' of the Jerkulator, but a little less gain-y and the highs a bit more 'ragged' or 'edgy'.
For leads, that makes it sound less synth-y than a stock Jerkulator, but switching to the neck pickup takes care of that.
For rhythm playing I find the nicest sound with the Fuzz control at maximum, but the guitar volume at 6 or less.  Then it does that nice chewy/gritty/crumbly overdrive that's not too fizzy (to my ears anyway).  Perfect for covering "Tequila Sundae" by Urge Overkill or second guitar on "Master of the Universe" by Hawkwind. 
With the guitar volume and Fuzz both at maximum, lower-string power chords are just a splatty, buzzy mess like a stock Jerkulator.  Which may be what you're looking for, I don't judge...

Notes:
All this is true on MY unit, built with the components as shown.  If you use different transistors, or change caps, all bets are off, and it's not that different from a Jerkulator.  Build one of those first, then breadboard my circuit and see what you get out of it.
Perhaps an audio taper potentiometer on the Fuzz control would work as well as tweaking the guitar volume, not sure.  All I know is that I have to turn the Fuzz down to 2 or so before it gets to that "grungy clean" territory that 5 or 6 on the guitar volume does.
My main guitar is fitted with Firebird-style mini-humbuckers.  Your sound may vary with single coils or full-sized humbuckers.

This will NOT do metal.

[replaceablehead]

Yeah that sounds like a Harmonic Percolator.

Mine gets splatty in the higher settings and if I roll the volume off to around 4-6 on the guitar with the pedal on full I get a ragged overdrive sound. It really rips and tears. The voicing is funny it sounds kind of distant, and dark, yet metallic and bright and cuts through all at the same time... very odd... actually it's a bit like a very mild %^&*ed wah, or treble boost, so the tone is more compact, that's with or with the diodes, but with the diodes it's like the whole thing is then put through a compressor. Add in the echo-y microphonic, slightly metallic reverberation that mine seems to achieve and it just sounds like a complete garage sound in one pedal.

The one thing I can't decide is if it sounds more like a valve amp, or a solid state amp, or transistor based pedal. One minute it sounds like Neil Young and the next it's the grating harmonic solid state metallic overdrive of Andy Gill with a parametric eq in front of it of course.

It's got issues though, I mean the distortion doesn't always sound great and it's hard to tame. I feel like this circuit could be the starting point for a legion of pedals that focused on exploring each of it's qualities.

I've found adjusting either guitar volume, or input volume does more or less the same thing, although I believe getting rid of the input pot would effect the loading on the pickups.

It was quite cold here the other day, and I put the central heating on before I started playing and when I first plugged in the HP sounded amazing, like gritty and amp like, just perfect, and then as the temperature in the room went up the volume on the HP went down and it started to get a bit fizzy around the edges and it lost that amp like tone and just started sounding buzzy and fizzy. Very frustrating. It wasn't too bad, but I think I noticed it more because of the contrast.

I can't help but wonder if germanium is a bit of a poor choice long term in the HP, I mean it sounds amazing, but because the circuit reacts so much to the hfe and leakage of the germ transistor that volatility is just so much more noticeable. I think I will make a jerkulator and live with both for a while.