Harmonic Percolator - make one!

[pinkjimiphoton]

i messed around with mine some, too.
i got it sounding great, but it wasn't quite unity gain.
i was like...wtf!!
so i said screw it, and went with all silicon... and found the sound i heard in the albini demo.
tho, to be fair, the sound he gets in that is NOT just the perc, it's got a fuzz in front of it.
i can tell, cuz i got the sounds pretty much identical by putting the escobedo jerkulator in front of it..
very cool... almost an octave, sometimes with octave down, too (in some ranges) and almost a 5th harmonic, too.
pretty savage.

my advice? socket... and just stuff in transistors until it make ya feel a little wiggle "down there".

[effection]

I don't know about when he's recording, but when I saw Shellac, the only thing he had was the Percolator and an MXR Noise Gate. He's more likely using it in front of the IVP's distortion circuit instead of a fuzz in front of the Percolator.

[midwayfair]

i got it sounding great, but it wasn't quite unity gain.

Huh.

Really?

Mine is insanely loud, and the transistors I used are not particularly high gain. It's at unity with the controls both at noon on the 1N695 side. On the OA126 side, unity is more like 10:00. Of course, mine is less fuzzy than others', so maybe it was just the different resistor values I used. :/

[pinkjimiphoton]

i tried all kinds of transistors, and in the end, went 100% silicon.
mine was just barely unity gain pegged, now it's at unity around 12:00.

[garcho]

I used all the components and values as the G Giblet schemo (used a film instead of a ceramic though, and electro instead of tant), with transistors from Small Bear. Definitely full on distortion, sounds great, and loud. Anyone hear the new versions? 300 bucks on Amazon, a little steep. I wonder how they sound? How accurate can the Albini video be if it's on youtube, on video, on your computer, etc.? Adds to the legend, I guess. Albini must be shocked that after spending a decade making underground, loud, noisy, harsh rock and roll that was never radio friendly, now (as in last 20 years) armies of dudes want the very same gear. Is it because of Big Black or Electrical Audio, or just because he produced Nirvana and the Pixies? All part of a grand Interfax marketing conspiracy

[hellwood]

for those of you less than impressed with this circuit, dig through your junk drawers for your leakiest dud transistors before you give up. Germanium for Q2 makes all the difference too...I was seriously about to scrap this thing after what I thought was an entire day wasted experimenting. Now I cant stop playing with it.

Q1 2n404 (610 hFE/6.1 leakage)
c 1.60
b 1.68
e 1.8

Q2 2n1302 (125 hFE/1.25 leakage)
c 1.88
b 1.86
e 1.81

EDIT:
I dont know how I blew it so bad and posted the wrong voltages, but these are the correct ones:

Q1 2n404 (610 hFE/6.1 leakage)
c 1.62
b 1.73
e 1.86

Q2 2n1302 (125 hFE/1.25 leakage)
c 1.93
b 1.62
e 1.85

also, this thing is LOUD with no lack of fuzz even with the leakiest Germanium transistors I could find in my reject stash. I also tried the 1n34A's and they were lifeless compared to the germanium transistors that I substituted for diodes. weird, but the clippers are obviously night and day critical for the warm and fat fuzz ...still waiting for some 1n695's. I would be interested to hear what others think of  experimenting with their leaky junk

[pinkjimiphoton]

i revisited this circuit again today too, figured i'd try some of the low gain ge russkies i just got in the mail..
tried a bunch of pos mp25b tophats, i bought 95 of 'em on the bay... 45 have arrived so far, and out of them, 20 read around 40-52 hfe. one read 80. i tried that in the perc.

didn't do it. tried ac128's...same deal. often, they sounded better turned around 180 degrees (the real leaky ones work better backwards, i think!!)

the mp25's didn't do it.

a 3906 in q1 and a mpsa13 in q2 was pretty good... all si, 300/950 hfe.

then i tried some nos JAN 2n2273/cgg7423p wb's i found recently at a surplus electronics place for a fair price... like a quarter a piece.
bingo...no, BINGO!!!

popped the first one i pulled out of the bag, and wango, that was it. about 45hfe with about 10ma leakage. perfect. could dial in some great tone from my guitar, from sparkly clean to full on fuzz with an almost octavia like bloom in the harmonics. at some settings of the guitar knobs, an octave down appears at some ranges.. it's faint, but it's there.

completely different animal.

300 bux on ebay?

i can beat that price... lol...

so i concur... them leaky rotten low gain ge's seem to do the trick.

i tried it all ge, but i preferred the silicon in q2. it's loud its rude, but man, what a cool tone.. some transitors sound ok, but kinda sputtery.
but the right ones man, it's the most fun you can have with your pants on!

i played this thing for 3 hours today. drove my family nuts. they won't talk to me, lol... but that's ok, cuz now i can build something new undisturbed.

[garcho]

i played this thing for 3 hours today. drove my family nuts. they won't talk to me, lol... but that's ok, cuz now i can build something new undisturbed.

like a true addict

[andrewgf]

I built one of these on breadboard and it's awesome.  I also built the harmonic fusion part on to it and found it sounded like a wah used as a filter.  It was interesting hearing the different harmonics that it brought out, but when I finally box it up, I think I'm just gonna build the percolator with only a volume knob.  Mine sounds best at full gain, using the volume knob on the guitar to clean it up if needed.  Put it into another low to med gain distortion it gets HEAVY.  I'm still fairly new to all this, though, and was wondering where I might be able to find alternate transistors to try out.  I just used a 2N404A and a 2N3565 from Small Bear.  

[garcho]

Check out Harmonic Jerkulator, by DIY titan Tim Escobedo. I never could get it to sound that good, probably user error. 

[pinkjimiphoton]

the jerkulator is pretty close! add a diode clipper to it...i did with mine. i like a jerk driving my perc!!

[andrewgf]

I'm going to build the jerkulator tonight and see how different it sounds.  I started with the "Albini" schematic from Madbean, but have subbed so many different parts I don't even remember what I've got in there now.  For the clipping diodes, I currently have a 4.7k resistor and a 1N34A on one side and a 1N34A and 1N914 on the other.

[pinkjimiphoton]

why the resistor with the 1n34?

the jerk is pretty close, once ya add the clipper. mostly it all comes down to the transistors imho.

[garcho]

why the resistor with the 1n34?

It alters the clipping on half the waveform, thereby altering the harmonics. Some other diode-clipping pedals do that.

[effection]

I'm going to build the jerkulator tonight and see how different it sounds.  I started with the "Albini" schematic from Madbean, but have subbed so many different parts I don't even remember what I've got in there now.  For the clipping diodes, I currently have a 4.7k resistor and a 1N34A on one side and a 1N34A and 1N914 on the other.

Wow, that's a huge difference in the clipping sides. How is that working out?

[andrewgf]

It has an interesting sort of compression to it.  It sounds pretty good.  I recorded samples of both the percolator and jerkulator with different clipping diode combos, and plan to go through and listen to them and pick my favorite two settings and put them on an on-off-on switch.  Looking at the waveform in my DAW, the series resistor with one diode clips the positive side quite a bit, leaving more dynamic range on the negative side.

[garcho]

Looking at the waveform in my DAW, the series resistor with one diode clips the positive side quite a bit, leaving more dynamic range on the negative side.

Yeah, positive or negative depends on the polarity and orientation of the diodes. But that's just how we conceptualize it, negative and positive sounds the same so it shouldn't matter which diode is in series with the resistor.

[pinkjimiphoton]

i was curious about diode clippers and did a little research...
you can tell which side of the wave is clipped by the orientation of the cathode of the diodes.
if the cathode (bar) faces down, it clips the top of the wave, if it faces up, it clips the bottom.
so you can use asymetrical techniques to clip the treble and bass completely differently..
say, led for more buzz in the lows, ge for sweeter highs.

god, i hope i didn't get that backwards!!

[effection]

It doesn't work like that. Top and bottom of a sound wave isn't treble and bass.

[pinkjimiphoton]

ummm... you sure?
if you look at how they work, on the waveform of an oscope, it indeed will work on the top or bottom...or both... of a sine wave.
if you clip the top of the wave, you clip the highs of the wave. if you clip the bottom, you clip the bass content. if you clip both, the highs AND lows will be distorted. that's why some dirt pedals sound better with just one diode clipping instead of the two you usually see (orange boss distortion comes to mind)
i may indeed be wrong, but after doing audio stuff for a couple decades, and looking at too many waveforms in my daw,
i'm pretty sure it indeed DOES work that way.
you can look at it, and see the way it sounds, if that makes any sense.