Harmonic Percolator - make one!

[pinkjimiphoton]

i used it live last night for the first time, it sounds a lot different thru my stage amp than my ruby..
definitely sounds better thru the smaller amp, much richer.
thru the big amp, it was kinda bright and shrieky, not quite as warm.
that said...before my fuzzface or klon it was amazing....and was doing all the stuff in albini's demos.
i think it needs to feed a moderately overdriven amp to really do it's thing as in steve's video demo of it.
so today, i may try and mellow it out a little with a strategically placed small cap, or i may try and find a less noisy/lower gain q2.
it's a bit above unity at full tilt, so that's good, too.

i likes it. gotta tweek it in a bit tho i think.

[pinkjimiphoton]

guys, any suggestions on how to make it a tad less shrieky?
i love how warm it sounds with the small amp, but thru my princeton it needs to shave about an octave off the top end..

and i gotta hit the solder joints, as it's popping and cracking a little...

i didn't, but i reccomend shielded cable to/from the switch.

off to mess with it...

and then i gotta find the jerkulator, for part 2 of SPT, the shootout

[midwayfair]

guys, any suggestions on how to make it a tad less shrieky?
i love how warm it sounds with the small amp, but thru my princeton it needs to shave about an octave off the top end..

and i gotta hit the solder joints, as it's popping and cracking a little...

i didn't, but i reccomend shielded cable to/from the switch.

off to mess with it...

and then i gotta find the jerkulator, for part 2 of SPT, the shootout

220-470pF or so across the volume pot might be the ticket. Easy to remove if it isn't, too.

Be careful about killing too much treble in this circuit early on (by e.g. increasing the 100pF cap) -- you can kill a lot of what makes it special.

Stock it has plenty of treble, but I wouldn't call it shrieky ... But then again, I like treble boosters, so maybe this guy's plenty is another guy's too much. (This is mine through a clean blackface-ish amp: http://www.youtube.com/watch?v=UoW2NUZewPY)

[digi2t]

220-470pF or so across the volume pot might be the ticket. Easy to remove if it isn't, too.

Uglyface fix. 

[Pyr0]

You could also try putting in that 1nf5 cap on the collector of Q1 to ground like in the pepper spray schematic.

[pinkjimiphoton]

thanks guys,
i will try both, see what sounds best. re-tubing my little homebrew monster at the moment, gonna let it idle a while.
i love that serendipitous feeling ya get when ya can plug in brand new power tubes and the freekin' bias is already close enough for rock and roll.

love.

so...either 1.5n  like the pepperspray, or small cap across the pot..i'm assuming you mean from input of the pot to ground, right?

sometimes i like a 100p cap across the input and wiper of the output pot on fuzzes, so you can turn it down and not lose all your sparkle.
wondering if maybe the combo may be magical..as this thing sounds best full blast, imho.

that way, i could tame the high end, BUT make it stay more consistent as turned down, i'm thinking..keep the tone the same, but still have volume control.

gonna go play. stay tuned!

thanks brothers!!

[midwayfair]

thanks guys,
i will try both, see what sounds best. re-tubing my little homebrew monster at the moment, gonna let it idle a while.
i love that serendipitous feeling ya get when ya can plug in brand new power tubes and the freekin' bias is already close enough for rock and roll.

love.

so...either 1.5n  like the pepperspray, or small cap across the pot..i'm assuming you mean from input of the pot to ground, right?

sometimes i like a 100p cap across the input and wiper of the output pot on fuzzes, so you can turn it down and not lose all your sparkle.
wondering if maybe the combo may be magical..as this thing sounds best full blast, imho.

that way, i could tame the high end, BUT make it stay more consistent as turned down, i'm thinking..keep the tone the same, but still have volume control.

gonna go play. stay tuned!

thanks brothers!!

Actually, I didn't realize you weren't using the 1.5nF cap. Do that first, as that's actually a HUGE amount of treble cut.

I meant putting the cap on lugs 1 and 3 of the output volume (that is, to ground). I don't think the other method of creating a treble bleed is appropriate here, especially because you've stated you prefer yours full blast.

Good luck ... hope you find a nice balance so it sounds good on both the Ruby and your stage amp.

[pinkjimiphoton]

i put a 22n across the volume wiper to ground.
huge difference...still a little hiss, but nothing like it was. gonna try a smaller cap, get a little more "sizzle" back.

it cleans up beautifully right now, but...i want a little bit more high end.. thinking, to my ear, 2.2n should be about perfect..

still messing with it.

part of the problem was i wired the dang switch backwards on the output.

and took the output from the INPUT of the volume pot to the switch, instead of the output. 

oops...figured that out when i tried putting it in the amp and noticed the volume worked in bypass. 

so i swapped it around, and discovered i'd totally f'd it up. lol...note to self: use more than two colours of hook up wire!!

stay tuned.. i have a feeling around 220p is gonna be the magic number, should give me about 2 octaves more high end, harmonic wise.

[pinkjimiphoton]

You could also try putting in that 1nf5 cap on the collector of Q1 to ground like in the pepper spray schematic.

ok, i just tried that. i didn't disconnect the cap across the volume pot, but imho, BINGO.

no more earwigs, and when ya turn the guitar down you still get the same tone. right on, pyro, good call!!

so... 1.5 (i used 1n)n cap (i used a green chicklet) between c and ground nukes the earwigs, and a 22n cap from wiper to ground on the level pot (i used, again, a chicklet) tames the rest. you lose a rch of ultra high end sparkle maybe (not enough to matter imho) but you nuke the noise down to like, boss pedal level. gonna try and videe it right quick..brb

[pinkjimiphoton]

[pinkjimiphoton]

revised vero

[digi2t]

DAMN YOU BROTHER!!!!....... DAMN.... YOU!!!!!!

All parts ordered.

Including some exotic ones.

Yes.... glass resistors.

Guilty as charged. 

[pinkjimiphoton]

lol

paybacks...   

[Mark Hammer]

Nice, ain't it? 

[digi2t]

I`m soooo glad you guys are on my side.

I think.....

[Pyr0]

That sounds good Jimi

[Morocotopo]

I hate you guys.

I HAD to make this, so Mark, if I take longer to make the Polyphase schematic, you know whose fault it is! Well, we can include Jimi there with his videos too!



Used the George Giblet schem. R1 is 2M8. Q1 is a 2SB175A, Hfe:60, leakage 147 uA. Q2 is a 2N3904, Hfe:167. Added a tone control, an A250K pot in parallell with the vol control, with a 6n8 cap from it to ground.  1N60 diodes (germanium). Tried a higher Hfe tranny for Q2, a 2N2222 close to 200, but it was howl city! Actually, with my guitar, the problem was that the bridge pickup fed back like crazy, seems to be the mounting springs are too loose, I could feel it shaking in my hand like mad. Neck one not so much.

Ok, I made a little sound file, just grabbed the guitar and made it, didn´t even tune it.
335 with humbuckers, direct into soundcard. Amp sim soft, set to a Twin, bright switch on, controls more or less at mid point. A bit of verb and ambience. The thing is on the breadboard, so noisy. Since it´s not a real amp, no acoustic feedback, and doesn´t have the live amp´s low end oomph and high freq hiss and stuff. with the amp the tone control is much more dramatic in it´s sweep, helps get rid of the brittle-y highs, depending how you set the amp´s controls. I really like the sort of "spongy" attack on the notes. In the sound file I play the same thing with the tone closed and then with the tone open, and later some noodling and guitar vol control fiddling. Doesn´t clean up as much as I want, that could be taken care of with a lower Hfe Q2 I believe, but I quite like the "all controls on full" sound, so...
Quite feedbacky with the 335 and a Hot rod Deluxe amp, in a nice way.
The file:

http://soundcloud.com/truemostro/harm-perc-with-tone-control

[Mark Hammer]

Well if that's how you're wasting your time, then I take full credit.

That's how mine sounds.  And yeah, the all-knobs-to-10 is fun because the sound is quite responsive to how hard and where you pick.  A hard pick-strum of a chord above a Tele bridge pickup gets this lovely "struzz" sound that's like bacon crackling (I'm not eating it, rabbi, I'm just listening to it!  ).  Switch to neck pickup and its a different sound, back off on the volume and again its a different sound.  So it's not like you even need to turn the harmonics control down all that much to get different tones, although I need to turn down to around 3:00 on the one I made the other day to nail what you got.

Clearly, from the long and informative 2008 thread, we are not alone in our admiration for this simple and pretty forgiving circuit.  But I'm happy to have provoked a little interest in it again, such that others could have some of the same pleasure.

[Morocotopo]

Credited.

Haven´t yet listened carefully to picking sensitivity, will do. And maybe try some lower Hfe Q2´s, to see if I can reach a satisfying balance between gain and cleanup ability. But it´s hard getting low Hfe silicons...

Yet another thing to box. I might try to fit this into the super duper mini boxes, but how will I fit two 16 mm. pots in there?

No, I can´t get 9 mm. ones here in Argentina, so don´t say it.

[Paul Marossy]

I hate this stupid circuit. I've rebuilt it and I can still only get it to squeal at various frequencies depending on how the knobs are set. No matter what transistors I use it just oscillates at a higher or lower frequency depending on what PNP transistor I use. When I play my guitar thru it, it sounds good if you ignore the constant oscillation.

I don't get it. I guess I'm just stupid for even trying.