Harmonic Percolator

Rare and sought-after box of confusion. Is it OD? Is it distortion? Truth is the Harmonic Percolator has a pretty unique tone of its own.

Famously used by the one and only Mr Steve Albini. Can't promise you'll nail his tone, but its a step in the right direction.

The pots are board-mounted pot for minimal wiring and simple enclosure mounting, and you can add an optional switch to take the diode clipping in and out of the circuit for two completely different sounds. Image shows the board-mounted micro-toggle switch, but you can wire a normal one offboard if you prefer.

***We've only gone and found a few 2N404 hidden away in the workshop. These really are the last. Once they're gone that's it. Please don't ask to be notified of it being back. It ain't coming. No sir. Sorry, only one 2N404 per kit.***

As 2N404 are getting harder to find we're now offering the kit with or without one, so you can still grab one when we're out of stock. You can try any PNP germanium in place of it for your own flavour percolation.

Partial kit: PCB, all board-mounted components (except 2n404 unless selected as an option), pots.

Full kit: As above, plus footswitch and appropriate daughterboard/components for your selected bypass type (see Downloads section for details of those), jack sockets, DC socket, battery snap, hook-up wire, LED.

Enclosure (pre-drilled) is only available with full kits, and will take a battery. Knobs are not included.

Builds are only available with full kits including enclosure. Please choose appropriate knobs.

Difficulty: Easy

PCB size: 50 x 22mm

Knobs required: 2

Enclosure: 1590B

Direct-Connect compatible (4-way)


Here's the older version.


Pedal Parts



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Customer Reviews

7 review(s) posted (write review)
Even order goodness 4 product stars
"Easy to build. Great sound. My only knock is mine can get a bit hissy when the "balance" is turned up past 1 o'clock." Rich - 22/03/2018
Very. Subtle. Death. / Bodies. Stink. In. Graves. / Uncovered. 5 product stars
"Niiiiiice. Very subtle. Kind of sweet sounding. With spikes. If anything, I like this best used with a fade pot, like on a mixer using the FX send, where u can fade in the amount of signal. Just tip it in the signal lightly. Synths really scream thru this. Easy build. Not at ALL what you think a FUZZ should be. Like I said... subtle. LOVE IT!!!" damnedcat777 - 20/05/2017
What. The. Actual. F##k! 5 product stars
"Get this pedal!! This has got to be the nicest sounding distortion I've ever used. I'm not messing about, it actually sounds beautiful. You're gonna think I'm a bit weird, but it's sort of, erm, friendly sounding. Told you. But it does! Honestly gorgeous sounding. I did accidentally blow my face off though, it's actually got a very high output. I had my amp volume low cos it's half nine or so and got a bit of a shock when I hit the switch. Well, Steve Albini said just have both controls at maximum. Don't do that. Not at first. Don't get evicted. Get this pedal, I shit you not, it's fantastic sounding. Thanks Lee. Wow." Mick Jones. - 17/03/2017
Great Pedal. 5 product stars
"Little did I know, when the Mrs asked me what I wanted for christmas, did i expect to actually get a HP(albeit one I would have to build). I've never built anything like this before and it was really straight forward due to the fantastic instructions and great PCB. I'm really pleased with the pedal, its way more interesting and dynamic than most normal overdrive/distortion pedals. I've just ordered a filth fack, got the bug. Great site, great products. Thanks Poodle." Charlie - 03/01/2014
Another addition to my pedalboard 5 product stars
"Fantastic sounding kit. Very, very dynamic to your pick attack but as noted in other review can sound very different depending on type of pickups used. I'm using it with the diodes removed (via the switch), this gives a load more output from the pedal and a gorgeous overdrive sound regardless of guitars used but its still a very distinctive sound. Great stuff!!" Simon - 09/05/2013
Harmonic Percolator Kit 5 product stars
"I'm a very happy customer. My kit arrived very quickly, and working at a very leisurely pace, took me around 5 hours to complete (could probably be done in an hour and a half if you were working quickly). There are two main reasons I decided to go for this kit - the fact that it includes the same rare, out of production transistors the original used (and at such a good price), and because you can select the 2n404's hFE (within small ranges). The hFE of both transistors (but particularly the 2N404)have a significant effect on the tone of this pedal, and the only other place I've found 2N404's available is ebay, all of which are both untested and expensive, which in my books is a recipe for wasting money. I opted for a 2N404 in the 181-200 hFE range and I'm very pleased with it. I'm also very impressed with the quality of the pcb, I never really understood what was so special about double-sided pcb's until I started soldering on this one - I found it much easier to consistently make lovely shiny joints. The pcb is also very compact, which is big plus. One important thing to note is that the nature of this circuit means that it is very sensitive to transistor hFE's, input impedance and output impedance. With the stock components even original HP's made in Milwaukee will sound uninspiring with some guitars, but amazing and totally unique with others. You can compensate for this by installing sockets and swapping different components in and out. I'm an insatiable tw" Taylor - 11/03/2013
Harmonic Percolator. 5 product stars
"My kit was the "old" vero board kit - the new PCB kits should be even easier to make. Great kit, with great instructions. Had to email about orientation of the transistors, and got a quick and detailed reply. Worked first time and makes my Tele sound super-mean! Superb service all round. I have just ordered the F zz F actoy kit." Mark - 20/02/2012

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Full kits DO NOT include enclosures unless you select them in the 'Kit Type' drop-down menu.

Don't forget to download the appropriate daughterboard build document for your kit:
Standard 3PDT