Talk to me about the harmonic percolator

Harry Klippton

Harry Klippton

Well-known member
Talk to me about the harmonic percolator. I've got a board for one (MAE One Knob Clang) that I'll put together soon, but I'm not very familiar with this one other than:

Things I know:
  • Associated with Steve Albini
  • Someone holds the rights to the name harmonic percolator and they're tight with it
  • There are two versions out there, effectively like an "original spec" one and an "Albini spec" one
  • My limited experience with playing one, it sounded absolutely awful. Clangy and metallic in a way that it was hard to see how that's what someone would want

what else is there to know on this one? I'm really just gonna build it cuz it's there and has a low parts count so why not?

what's your favorite example of one in use? Any tips for stuff relating to the circuit? Do you love this circuit?
 
I picked up a board but haven't built it yet. I bought it entirely because I had already built the topographer and read somewhere that albini likes to combine those circuits. It feels like I can't form a complete opinion on the topographer without using it "the right way."
 
Interesting to hear that you found it metallic and clangy. It’s been a bit since I’ve played one, but I don’t remember having that takeaway. Of the ‘Albini’ and ‘stock’ specs, I believe the ‘Albini’ is a bit more controlled, but the ‘stock’ specs weren’t unusably outrageous. A diode switch is a nice touch, as the ge clippers suck a lot of volume.

I’ll revisit a build and provide some better feedback hopefully soon.
 
The Antithesis (Karma Suture) is another variant. It's been on my radar because it looks like a more tweakable version and the demos seem pretty good.

As for Albini, I am a casual fan of his band Shellac, and appreciate what they do, but that guitar tone is not the tone I seek.
 
The 'Albini' spec is indeed a smoother and more controlled version of this circuit. By itself through a clean amp, I can't say that the Percolator is a great fuzz. To me, this one works best when pushing an amp that is either right at breakup or already broken. What it does best is give off a more harmonic rich tone for an amp to work with...that and a bit of fuzz to boot depending on how high you set Harmonics.

As Albini found, add this in front of an IVP preamp and you get a rather harmonic rich tone. Can do the same with other preamps, amps, overdrives, etc. Just have to experiment with it a bit.
 
I just made the PedalPCB board for it. I used matched transistors from SB.

I love it. To me, it is like a “hairier” tonebender. The range of fuzz is greater and it can get thicker than the Tonebender. It has not forced me to remove my Tonebender, because I think there is enough difference to keep them both.

This may be controversial, but if a Big Muff and a Tonebender had a baby, it would be a Harmonic Perculator….
 
I recently bought a Drunk Beaver Secret Sauce pedal and, after trying it, it made me revisit this circuit. I built two different Percolator clones, the AionFX Particle and Calliope, and found that they're both quite different than the Secret Sauce pedal. By comparison, the Secret Sauce is a more gnarly fuzz with more gating when Harmonics and Compression are reduced. Whereas the two AionFX pedals I built are smoother and more controlled. Really has me wondering what the main difference is.

I built the Particle first and really liked it. It appears to stick to the original circuit but adds a switch for a few different clipping options. The default specs are for the Albini version but the documentation does list the components for a stock Percolator. I then built the Calliope, which is Catalinbread's take on the circuit. It appears to be somewhere between a stock Percolator and the Albini version. It's a bit more flexible. Tonally similar to the Particle though.

So with the gated nature of the Secret Sauce pedal, I'm gonna breadboard a PedalPCB Percolation Station and look at the differences between these pedals. I'll start with the same transistors I'm using in the Particle and go from there. I'm curious if the reason mine aren't gated is due to the low gain transistors I'm using. That and likely the differences between the stock and Albini. All of this has me wondering about this circuit.
 
I'm just finishing up watching the videos linked in the pepperspray doc and I gotta say I do think this sounds pretty good. Perhaps the one I played was not a very good example.
 
I built one. Ended up taking out the diodes. It can be a very open sounding pedal. Great for chords if you don't crank the gain. Cheap easy build even if you don't have a premade board. It's a very unique sounding pedal and loud as hell. I ended up taking out my diode and transistor switches and put in a mosrite fuzzrite of a switch. Forgive my terrible paint job. This was pretty early on in my building days. IMG20230306110251.jpg
 
I had built the Particle, (Albini mod), and it didn’t make it through the honeymoon. But then this week, tried it with my one humbucker guitar, and I got it—really can be a subtle (or not!) enricher. Pretty addictive. So, total thumbs up with humbuckers. (This is a lower wind, neck only Eastman thinline jazz box; I imagine the more closed in (or dead sounding, in my opinion) higher powered humbuckers would greatly benefit from this, or a similar exciter.)
 
I like the HP. Weird and unruly. Some pretty horrific sounds have come out of the HP clone I got, but then some pretty fantastic distortion toan has snuck out when using it on a less compressed setting to push my amp.
 
Chuck D. Bones said:
It's tricky to get the biasing right on the HP. Not sure I've managed to get it quite right.
Click to expand...
What would that even sound like? I'm not sure it's possible to get the biasing right. Well - maybe not true, I've found that the resistor going to the silicon (Q2) collector really can only be 91K in order for the circuit to act predictably in any way.
 
I've made a number of HPs with this schematic using pairs of R591/2N4401 and MP41/KT315. On both, the 680K feedback resistor on Q2 is less usable (to my ears). The "Fuzz" control is pretty neat, it acts both as a gain knob and in certain sweet spots can bring out subharmonics.

335 MK. I.jpg
 
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