Author Topic: Harmonic Percolator - make one!  (Read 118514 times)

pinkjimiphoton

Re: Harmonic Percolator - make one!
« Reply #140 on: October 25, 2012, 09:33:14 PM »
no worries, dino, just wanted to make sure somebody didn't think it was right and get dissappointed.

'sides, now i got YOUR layout to go with. works for me!! ;)
listen loud. blaze one first:
https://drive.google.com/open?id=0BzMJxNNgY3_yc0JNd0VqdmNIWEk

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LP Hovercraft

Re: Harmonic Percolator - make one!
« Reply #141 on: October 25, 2012, 11:51:03 PM »
@ Mark-I will have to play with it a bit to see if I can get the Octave up sound.  It seemed to have the best sound (to my ears, anyway) with a leaky ge transistor in q1.  I remember trying a tightly spec'd 2N404 from Small Bear as q1 and it did not sound very good.  Yes, it must be bandwidth limited just at the right place in upper register somehow-one of the few 2 knobbers that truly do not need a tone control. 

DougH

Re: Harmonic Percolator - make one!
« Reply #142 on: October 26, 2012, 07:07:26 AM »
Part of the bandwidth limiting I believe is due to the low input impedance and the way it loads your guitar pickup. The Rangemaster and Fuzz Face both behave the same way. The low impedance load will roll highs off of your guitar signal. And at the same time, when you turn the guitar down it will get clear and bright. I suspect there's not much more to it than that, other than the passive electronics in your guitar which affect it as well But in the end, I believe it's due to the interaction between the guitar circuit and the input to the fuzz circuit.

"I can explain it to you, but I can't understand it for you."

Mark Hammer

Re: Harmonic Percolator - make one!
« Reply #143 on: October 26, 2012, 09:59:35 AM »
Part of the bandwidth limiting I believe is due to the low input impedance and the way it loads your guitar pickup. The Rangemaster and Fuzz Face both behave the same way. The low impedance load will roll highs off of your guitar signal. And at the same time, when you turn the guitar down it will get clear and bright. I suspect there's not much more to it than that, other than the passive electronics in your guitar which affect it as well But in the end, I believe it's due to the interaction between the guitar circuit and the input to the fuzz circuit.

Which would also imply that it would sound "best" when placed in an uninterrupted path path from the guitar, rather than preceded by anythng between guitar and Percolator that might offer a low-enough output impedance.  Does that strike you as sensible?

pinkjimiphoton

Re: Harmonic Percolator - make one!
« Reply #144 on: October 26, 2012, 10:39:49 AM »
i run it first, before my fuzzface even.
listen loud. blaze one first:
https://drive.google.com/open?id=0BzMJxNNgY3_yc0JNd0VqdmNIWEk

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tca

Re: Harmonic Percolator - make one!
« Reply #145 on: October 26, 2012, 11:11:32 AM »
So, I dind't have the parts for the Percolator, so I've breadboard Escobedo's Jerkulator with two pairs of silicon diodes at the output and with the transistors 2N4401/2N4403. I couldn’t believe my ears!! Here is the sound clip from a portable mp3 recorder with a 1W solid state amp with a 3'' speaker. Need to fix the frequency response, but it took me about 15m to breadboard it!


Cheers.
« Last Edit: October 26, 2012, 11:20:02 AM by tca »
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DougH

Re: Harmonic Percolator - make one!
« Reply #146 on: October 26, 2012, 11:49:38 AM »
Part of the bandwidth limiting I believe is due to the low input impedance and the way it loads your guitar pickup. The Rangemaster and Fuzz Face both behave the same way. The low impedance load will roll highs off of your guitar signal. And at the same time, when you turn the guitar down it will get clear and bright. I suspect there's not much more to it than that, other than the passive electronics in your guitar which affect it as well But in the end, I believe it's due to the interaction between the guitar circuit and the input to the fuzz circuit.

Which would also imply that it would sound "best" when placed in an uninterrupted path path from the guitar, rather than preceded by anythng between guitar and Percolator that might offer a low-enough output impedance.  Does that strike you as sensible?

Yes.
"I can explain it to you, but I can't understand it for you."

digi2t

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Re: Harmonic Percolator - make one!
« Reply #147 on: October 26, 2012, 12:01:15 PM »
Something struck a chord (pardon the pun) with me last night. I was reading Gus' analysis of the circuit, when this jumped out at me;

Quote
If you look close it is just two simple gain stages in series: HOWEVER the 47uf sets up how much the current drain in each stage interacts. This is most likely the cause of the musical feedback in the video. Work out your gain phase and current draw.
 
The 47uf is most likely one of the big tuning points in the circuit make it bigger and smaller and hear what happens. The emitter node voltage is also important. If it is 9V supply and 4.5V both sections get 4.5V as a supply voltage. If it is 5V the NPN gets 4VDC and the PNP 5VDC. If it is 3VDC the NPN gets 6VDC and the PNP 3VDC etc.
 

Before I go any further, I'll just mention that I added a 100K pot to the input. What DouH said about loading bothered me. So 100k pot in, and no pot on the out, direct to amp. Pot is maxed during my tests.

So, back to what Gus said. I started rummaging through my capacitors, and found two things;
1) If I lower the 47uF to 4.7uF, raise the cap between the two trannies to 0.1u, and work the trimmer on Q1C, then yes, I do get sub-octave. But, in my case, it's not stable, ugly, and I get oscillation as well. If I turn down the 100K pot, it goes away, but the circuit sounds lifeless.
2) If I go with a 6.8uF tantalum, in place of the 47uF, and return my cap between the two trannies to my original value of 0.01uF, a huge grin appears on my face. Now, the octave up bloom appears slightly more pronounced, and my root notes/chords go into feedback at a much more sane amp volume level. The octave bloom just continues to bloom into sweet feedback. OH HAPPY MAN!!
3) THE sweet spot with a 6.8uF tant is now 1.0v on Q1C. Plucking a note while working the trimmer, as soon as I get close to 1.0v, it's... it's... well, let me put it this way; it finds Jesus. :icon_lol:

At the moment my voltages are;

Q1
E - 1.146
B - 1.049
C - 1.015
Q2
E - 1.146
B - 1.675
C - 2.256

Everything else is unchanged on the board, it's as I drew the vero, except for the 6.8uF replacing the 47uF.

Freakin' crazy!! :icon_cool:
« Last Edit: October 26, 2012, 12:11:11 PM by digi2t »
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wavley

Re: Harmonic Percolator - make one!
« Reply #148 on: October 26, 2012, 12:01:49 PM »
Part of the bandwidth limiting I believe is due to the low input impedance and the way it loads your guitar pickup. The Rangemaster and Fuzz Face both behave the same way. The low impedance load will roll highs off of your guitar signal. And at the same time, when you turn the guitar down it will get clear and bright. I suspect there's not much more to it than that, other than the passive electronics in your guitar which affect it as well But in the end, I believe it's due to the interaction between the guitar circuit and the input to the fuzz circuit.

Which would also imply that it would sound "best" when placed in an uninterrupted path path from the guitar, rather than preceded by anythng between guitar and Percolator that might offer a low-enough output impedance.  Does that strike you as sensible?

Yes.

So, it might be a good idea to try an AMZ pickup sim in this thing if you don't want it first in your rig?  I put one in my fuzz face and it's certainly close enough for rock and roll.
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DougH

Re: Harmonic Percolator - make one!
« Reply #149 on: October 26, 2012, 12:57:52 PM »
Part of the bandwidth limiting I believe is due to the low input impedance and the way it loads your guitar pickup. The Rangemaster and Fuzz Face both behave the same way. The low impedance load will roll highs off of your guitar signal. And at the same time, when you turn the guitar down it will get clear and bright. I suspect there's not much more to it than that, other than the passive electronics in your guitar which affect it as well But in the end, I believe it's due to the interaction between the guitar circuit and the input to the fuzz circuit.

Which would also imply that it would sound "best" when placed in an uninterrupted path path from the guitar, rather than preceded by anythng between guitar and Percolator that might offer a low-enough output impedance.  Does that strike you as sensible?

Yes.

So, it might be a good idea to try an AMZ pickup sim in this thing if you don't want it first in your rig?  I put one in my fuzz face and it's certainly close enough for rock and roll.

Yes, you need to treat this like any vintage fuzz with a low input impedance.

And for digi2t: The 100k pot on the input won't affect the impedance much. The input impedance will basically be constrained by the input impedance of the transistor, which is pretty low, typical for a BJT like this. That's why vintage fuzz circuits using BJT transistors typically have low input impedance which loads the guitar pickup and is part of the "sound". Unless you bootstrap the first stage, a la Gus's NPN Boost, a typical BJT gain stage like this will be low Z.
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digi2t

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Re: Harmonic Percolator - make one!
« Reply #150 on: October 26, 2012, 01:29:25 PM »
Quote
And for digi2t: The 100k pot on the input won't affect the impedance much. The input impedance will basically be constrained by the input impedance of the transistor, which is pretty low, typical for a BJT like this. That's why vintage fuzz circuits using BJT transistors typically have low input impedance which loads the guitar pickup and is part of the "sound". Unless you bootstrap the first stage, a la Gus's NPN Boost, a typical BJT gain stage like this will be low Z.

Got it Doug. I just wanted to eliminate any and all possible variables here. Bit of a pain when something sounds one way on the board, and then different boxed, especially if it's due to cutting corners when I had it on the board. :icon_mrgreen:
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digi2t

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Re: Harmonic Percolator - make one!
« Reply #151 on: October 26, 2012, 03:17:53 PM »
CRAP!!!

It was too good to be true. Nix on the 6.8uF. I finally got the chance to crank it up more to, ahem, "stage" levels. Problem is the there is a short oscillation "after howl" that occurs whenever you hit chords hard. So, 6.8uF is out.

10uF tant sounds pretty good though. Better than a high-end ELNA cap that I tried. But, 10uF has a drawback; doesn't clean up as well as a 47uF when you roll of the volume. I have a 33uF Philips axial in right now, and I think it's the best compromise to date. Good harmonic content, feedback attainable (though higher volume is needed), and cleans up pretty decent.

I get the feeling this thing is telling me to stay between 22 and 47uF.

I also reduced the cap on Q1C to ground to 0.0047uF. I saw that the Collins clone uses a 0.001 here, but I couldn't hear a difference between 0.001, and nothing. 0.0047 is a good compromise between the 102, and the 103 I was using. It's just enough to kill the noise from the tranny, while being less buzzy than the 0.01.

Ah... the joys of breadboarding! The saga continues...
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pinkjimiphoton

Re: Harmonic Percolator - make one!
« Reply #152 on: October 26, 2012, 03:40:55 PM »
yah, them's the breaks bro...

when i first built this, i was amazed...thru my ruby.
when i played it thru my princeton, i realized there was a humongous difference.. a little tweaking tho, and now it sounds pretty awesome!! ;)
listen loud. blaze one first:
https://drive.google.com/open?id=0BzMJxNNgY3_yc0JNd0VqdmNIWEk

I stand for Truth, Justice, and the American Way. @#$% TRUMP! YOU ARE EITHER ANTI FASCIST, OR YOU ARE ONE. #BLM

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Gus

Re: Harmonic Percolator - make one!
« Reply #153 on: October 26, 2012, 05:36:17 PM »
I built two Si versions
One a PNP 2n2907 and NPN 2n2222
And an all NPN 2n2222
I did change the circuit a little I increased the collector currents and adjusted the feedback bias resistors.


pinkjimiphoton
yah, them's the breaks bro...

when i first built this, i was amazed...thru my ruby.
when i played it thru my princeton, i realized there was a humongous difference.. a little tweaking tho, and now it sounds pretty awesome!! ;)

If I adjusted effects for friends of mine I would ask them to bring there stage amp, guitar(s), and signal cords that they used live.  I would then ask the play at stage volume and explain what they wanted to change.  I would adjust the circuit(EQ, gain, bias etc) and then we would test again.  One thing I noticed is often you want a thin sounding effect when tested it at low volumes in a house for distortions and fuzzes at stage volume.  A few things are going on how the players share the frequency range, if the guitar has open back speakers thing can sound bad when the volume is turned up if you have to much bass, and there are other things.

digi2t
Thanks for doing the cap value and type test at the two emitters.  I never got around to testing this tuning point.
« Last Edit: October 26, 2012, 05:39:52 PM by Gus »

Paul Marossy

Re: Harmonic Percolator - make one!
« Reply #154 on: October 26, 2012, 06:18:13 PM »
Well I finally got mine to work. It wouldn't work because I did something so shockingly stupid that I can't even mention it.  :icon_redface:

Anyway, I did the Giblet version with a few tweaks:

Q1 is a 2N1108 with an Hfe of about 62
Q2 is a 2N2222 with Hfe of about 125
R2 is a 510K
C3 & C6 are 0.15uF
R4 is a 50K trimpot. Sounds best to my ears at about 6.8K
50K balance pot
100uF power supply cap added
0.001uF cap from Q1 collector to ground
0.0022uF cap from output of balance pot to ground




pinkjimiphoton

Re: Harmonic Percolator - make one!
« Reply #155 on: October 26, 2012, 06:43:14 PM »
MUST...HAVE...CLIPS!!!!!!!!!!!!!!!!!!!!!!![/color]

 :icon_eek: :icon_eek: :icon_eek: :icon_eek: :icon_eek: :icon_eek: :icon_eek:

PROPS ALL AROUND, I HOIST THIS HERE BREWSKY TO ALL YA'LL!

 i found the jerkulator i built, and listened to it a little... i think it has the flavor of the perc, but doesn't have the same sound.
pretty much the only difference i think is gonna be the diode clipper.
listen loud. blaze one first:
https://drive.google.com/open?id=0BzMJxNNgY3_yc0JNd0VqdmNIWEk

I stand for Truth, Justice, and the American Way. @#$% TRUMP! YOU ARE EITHER ANTI FASCIST, OR YOU ARE ONE. #BLM

#FuzzyGoodness

digi2t

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Re: Harmonic Percolator - make one!
« Reply #156 on: October 26, 2012, 07:17:16 PM »
Quote
Well I finally got mine to work. It wouldn't work because I did something so shockingly stupid that I can't even mention it. 

Way to keep us up at night, wondering...

 ;D
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Paul Marossy

Re: Harmonic Percolator - make one!
« Reply #157 on: October 26, 2012, 07:24:22 PM »
Quote
Well I finally got mine to work. It wouldn't work because I did something so shockingly stupid that I can't even mention it. 

Way to keep us up at night, wondering...

 ;D

Ha ha, right. I think this was the dumbest mistake I ever made. My days are just too long sometimes...  :icon_wink:

DougH

Re: Harmonic Percolator - make one!
« Reply #158 on: October 26, 2012, 09:22:13 PM »
How does it sound, Paul? How do you like it?
"I can explain it to you, but I can't understand it for you."

pinkjimiphoton

Re: Harmonic Percolator - make one!
« Reply #159 on: October 26, 2012, 10:31:05 PM »
c'mon, paul fess up...

i bet i've done  WAYYYYYYYY dumber. probably on every build!! ;)

the important thing is it's alive!!

we need clips!!!! ;)
listen loud. blaze one first:
https://drive.google.com/open?id=0BzMJxNNgY3_yc0JNd0VqdmNIWEk

I stand for Truth, Justice, and the American Way. @#$% TRUMP! YOU ARE EITHER ANTI FASCIST, OR YOU ARE ONE. #BLM

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