Harmonic Percolator - make one!

[Paul Marossy]

How does it sound, Paul? How do you like it?

Sounds pretty good I think. Need to spend some quality time with it to really get to know it better... 

[Morocotopo]

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. 

Paul, you know we´ll bother you till you tell us what the problem was...

Confess!!!!!



I´ve done every possible thing to make my circuits NOT work, such as forgetting to put the IC´s in the board, not connecting power, parts orientation wrong, misplaced parts, etc etc. You think that after some time, you are an "experienced builder", but then the dumbest thing brings you back to earth. That´s life.
Congrats on making it work.

[Paul Marossy]

OK, I had it unboxed and had the input and output jack grounds connected together, but forgot to connect them to the circuit ground. Really really really dumb mistake. That's what happens when you get up at 4:00am, work 10 hours and then try to build a circuit at the end of the day when you are exhausted. 

[pinkjimiphoton]

paul, i got ya beat...the original video i shot?

i had the INPUT to the level control going to the footswitch, rather than the output...so it was looped around backwards.
couldn't figure out what the hell i got wrong til i looked at it hard!!

so....in bypass, it was bypassed thru the volume pot. and wired backwards.

when i figured out i had the bypass wrong, i fixed it...and nuked the pedal, cuz i didn't notice where the output was actually COMING from..now, in bypass, the pedal went dead.


figured it out eventually...forgetting a ground? dude...i do that wayyyyyyyy too often!!

[Paul Marossy]

That sort of stuff happens to all of us once in a while I guess.

[pinkjimiphoton]

seems to happen to me on a daily basis!! 

[effection]

Hey! I usually just lurk around here, but I figured I'd jump in and give my two cents on this circuit, some notes and observations, since I've worked on making variants of this for a few years now.

It originally started when a friend of mine was way into the Black Keys and wanted a crazy fuzz tone to do that style stuff. I made him a quick Percolator variant out of whatever I had on hand, and it made for a sweet pedal.

I used a 4403 for the PNP and a 3904 for the NPN. My new Percolator variants use a Russian GT308A. This won over the MP16 (which I found strange, since it's the equivalent to the original 404A, I think) and an AC188 (not surprising, I've learned to hate those things).

For diodes, I use these black OA126 germanium ones that are really awesome. These are best if you're adding a clipping switch with silicon and germanium options, as the forward voltage is about .72-74 on the ones I got, so it can be easily put on a switch with 914's and you don't get the volume drop in comparison like with 1N34a's or similar germaniums.

I took out R6 (consensus schematic). I replaced this with a low-voltage germanium diode like a 1N34a. There are other cool options here like the AMZ warp controls for different clipping effects. This is a pedal that really benefits from that.

A personal touch that really doesn't make that much of a difference is that I put the diodes in the feedback loop of Q2 instead of after. This was honestly because it fit better in my layout. I played around with it, and I couldn't really tell, so it stuck like that. I think this makes it a bit more conventional anyways, a la Big Muff.

I never tried the 1n5 cap from the collector of Q1 to ground, but that honestly makes total sense and is something I should start doing. Before that, I also took note of the Big Muff and put a 470p cap in the feedback loop of Q2 to tame out the high end. (notice how my second gain stage is looking more and more like a Big Muff gain stage?)

I also played with some values, and here is what I seem to like (from consensus schematic):

R1 - 680K                                                                              C1 - 100p
R2 - 220K                                                                              C2 - .022uF
R3 - 100K                                                                              C3 - 1uF
R4 - To taste. Honestly anywhere from 22K-130K                C4 - 22uF
R6 - 1N34a ge diode                                                             C6 - .1uF      

[effection]

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.

Why don't you try something like this? Dial in anywhere from 10 to 43

[pinkjimiphoton]

hey, that's a great idea!!

[effection]

Let me know how it goes. I'm curious if that's a good knob to have on the pedal.

[pinkjimiphoton]

i may be knocked back for a few days, depending on frankenstorm... 

[digi2t]

i may be knocked back for a few days, depending on frankenstorm... 

Batten down the hatches, and stay safe bro.

[Jazznoise]

Hurricane Sandy? I wish they'd make the names a little better. Hurricane Holocaust, or maybe Hurricane Brofist Your House.

I'm boxing my Octavia tomorow. I can't get any Ge Trannies till Monday week, so please keep the information trickling in as that means it'll probably be a month before the thing gets built! 

[effection]

1. Frankenstorm is a fantastic name for a pedal.

2. On that mod I drew up, I think maybe a 50k pot would be a good call. If it isn't enough to block the 33uF cap entirely, it may be a 13-43 range. 100k would definitely do it, but the range won't be as fine tuned, i.e not much of an impact at the beginning and then a huge jump in capacitance towards the middle.

[pinkjimiphoton]

maybe a stacked pot, with a cap on both side, and a smaller, median value in the middle?

yah...FRANKENSTORM!!!

LOL

the gov was on the idiot box, telling people to be careful. truth is, they don't know what the heck is gonna happen..
i mean, a hurricane crossed with a northeaster and some other weirdness?

won't stop my jam i host on tuesdays, unless the power goes out. that's the phattest drag, not being able to indulge my solder addiction..lol

[bluebunny]

Hey Jimi - hope you weather that storm safely, and all our other friends in those parts.  Stay safe!  And enjoy your Tuesday jam, of course. 

[Paul Marossy]

won't stop my jam i host on tuesdays, unless the power goes out. that's the phattest drag, not being able to indulge my solder addiction..lol

Hurry, build a few battery powered amps! Or get a small generator. 

[pinkjimiphoton]

i gotta ruby amp i built, a box full of 9volt batts, and 7 milkcrates full of pedals to play with, i'm cool, let the power failure commence!!

thanks guys... more worried about oldschoolanalog (dave wiener) cuz he's right where that sh*t is gonna make landfall.

and my kid, about a 10 minute walk to the beach on the coast of southern maine.

[pinkjimiphoton]

ummm, guys, check out what arph came up with on the "other forum"....

http://..........org/viewtopic.php?f=6&t=20017

hot DAMN!

[~arph]

This forum should support attachments too  

Its a harmonic energizer into a harmonic jerkulator.. forcing all the harmonics together in the Harmonic Fusion Engine  

Anyway... since it's my schematic I might as well post it here too... apologies for the size, but it's readable now..

EDIT: and the soundclip:  http://soundcloud.com/arrfx/harmonic-fusion-engine


It's on dropbox so grab it while it lasts..