INTERFAX: Harmonic Percolator (modded)

This is a slightly modded Interfax Harmonic Percolator that I made today.  It's an odd little circuit - it can run from clean, a bit overdriven, then into distortion, and finally to overly compressed fuzz madness.  The range of sounds are so broad, it's almost worth setting it up as a dual pedal (which I might do). 

In terms of mods, it's kind of a mix of a couple of schematics, the Land Devices HP-2 and a bit of my own thing.   It's still very much a Harmonic Percolator, that much is sure.  If you want to use the layout for a stock Harmonic Percolator (whatever that may be), there's fairly extensive discussions on the usual forums, including schematics and of course many and varying opinions as to what it should be.

INTERFAX HARMONIC PERCOLATOR - MODDED VERO LAYOUT

When it was on the breadboard I tried a few different transistors.  The differences were noticeable, and I'd recommend testing before soldering, to make sure that you have a combination that you're happy with.  

If you have a breadboard, it's worth getting it on there to play with - there are so many variations on this circuit, and they do make a difference.

The silicon transistor had a hFE of around 240 and the germanium was about 70 with almost no leakage (like many soviet transistors).  The type of germanium and silicon diode is not important.   

ON THE SCOPE

With the input trimmer down, it's a pretty clean signal (called Harmonics on the pedal).  I run a 200mv 440hz sine wave into my scope.

This is with harmonics on full, it's a fairly over the top and very compressed fuzz sound.  Germanium diodes are on.

This is Harmonics on full, diode clipping bypassed - there's a huge jump in level and it's a lot more dynamic.  

INTERFAX: Harmonic Percolator, Albini Values, 0.15" Vero Layouts

Since I've been on a bit of a Harmonic Percolator thing lately, I thought I might do some 0.15" mojo layouts using Albini / Mad Bean Pepper Spray values.

Here's one built by Sean of Spiller Instruments.  Looks great, as do his other builds. 

INTERFAX HARMONIC PERCOLATOR, ALBINI VALUES - VERO LAYOUTS

CATALINBREAD: Karma Suture, Silicon Version

Silicon version this time, as it was pretty similar to the hybrid silicon / germanium version.

Link to schematic

Link to tracing journal on Aion FX

CATALINBREAD KARMA SUTURE, SILICON VERSION - VERO LAYOUT

VIDEO DEMO

CATALINBREAD: Karma Suture, Germanium Version

 A nice Harmonic Percolator variation from Catalinbread.  They've kept the bones of the original, and have added an input capacitor blend, as well as a pot to dial in the diodes on the output.

Link to schematic

Link to tracing journal on Aion FX - and think about buying one from Aion 

CATALINBREAD KARMA SUTURE, GERMANIUM VERSION - VERO LAYOUT

GERMANIUM VERSION - VIDEO DEMO

Haven't done a tag board build for a while - so here's a classic.  

INTERFAX HARMONIC PERCOLATOR HP-1 - TAGBOARD LAYOUT

Being tag board, I've used 1/2w resistors and axial caps.  You could use something more practical (smaller), but if that's what you want to do, I would recommend using a different layout, as this is not the best use of space for regular-size parts.  

I would recommend breadboarding this prior to committing to solder.  The Interfax Harmonic Percolator is very tweakable, and sometimes takes some adjusting to get it right.  

There's pages on the Harmonic Percolator on DIY Stompboxes.

INTERFAX HARMONIC PERCOLATOR - POINT TO POINT LAYOUT