Harmonic Percolator (with some mods)

[xefned]

Wow! It's everything you could want in an HP. Thanks for all the detailed notes on dialing in the lower octave. I love that you found a way to switch diodes without a massive volume jump. That mod could come in handy on so many builds.

I also like the flush-mounted outtie jack. Really impressive work!

 

[geoffrey]

I was about to post some shitty, sophomoric build report because I haven't in awhile, but after coming across this masterpiece, I deleted it posthaste. Beyond inspirational, bro. Keep'em coming!

 

[Coda]

Still hard from this one…

 

[xefned]

Is Ube the same thing as Vbe? Anyone know?

 

[giovanni]

Is Ube the same thing as Vbe? Anyone know?

View attachment 75535

Yeah it should be.

 

[xefned]

Yeah it should be.

Thanks, man. I just found a post from Señor Bones indicating so.

 

[xefned]

I was about to post some shitty, sophomoric build report because I haven't in awhile, but after coming across this masterpiece, I deleted it posthaste. Beyond inspirational, bro. Keep'em coming!

I wanna see all the builds! Anything DIY is something to be proud of.

…Octave down ... WANT!

I know man. I love the Harmonic Percolator so much. But with some down octave too? Subtle notes of another favorite pedal: the Blue Box. But the Blue Box's demonic PLL-sounding octave down is overkill sometimes.

Some octave mixed in with the Percolator sounds like sonic heaven.

 

[Fingolfen]

Holy crap... that is effing amazing!!!!

I've messed around with the percolator a bit... I need to play around with it more...

 

[Guilherme Collateral]

Whoa! That's really awesome looking inside and out. Great work!

 

[eurobailey]

Thanks so much for the effort in a) researching this build and b) taking the time to share your findings.
I am keen to build one of these after finding the layout on amplified parts. I am planning on using a turret style build and the steve albini schematic. Given this style of layout, the detail in the mods you have done may be hard to replicate in a turret v pcb build. So my plan - after breadboarding is
* use a low gain, low leakage GE transistor with a low VBE. I have a 2n404 so will look at that.
* Modify the 750k resistor (increase).
* Change the q2 collector for a pot. This seems to be a common mod - help tune the octave but also should help to bias the transistor and get some gated effects ? Did you have a preferred HFE for the silicon transistor?
* look to find low VF diode. I may go the switch route - and go GE diode, no diode and rather than silicone use a shkotty instead? I undertand i will get an out put change when flipping diodes however cannot see myself doing this mid song etc.... and the volume out put fix looks like a bit of work?
* The symmetry pot - if i just used this on the diodes - do i have to use the dual gang pot? This part i was a little confused by?

 

[PedalBuilder]

Thanks so much for the effort in a) researching this build and b) taking the time to share your findings.
I am keen to build one of these after finding the layout on amplified parts. I am planning on using a turret style build and the steve albini schematic.

You're welcome! It's a very fun build. That said, if you want to build an Albini-spec Harmonic Percolator I wouldn't use the information here as the basis for your build. Despite the similar circuit topography, the Albini-spec is a very different effect from what I built.

 

[eurobailey]

Thanks for the prompt reply. Does that mean the original Albini HP doesnt have the sub octave effect? Whilst I understand you have taken the original schematic and made some big changes to 'increase the sub octave' if i make the suggested changes as per my post would i Not get somewhere between the two?

 

[PedalBuilder]

Thanks for the prompt reply. Does that mean the original Albini HP doesnt have the sub octave effect? Whilst I understand you have taken the original schematic and made some big changes to 'increase the sub octave' if i make the suggested changes as per my post would i Not get somewhere between the two?

There are a couple different Harmonic Percolator schematics floating around out there. One is the "Albini-spec" schematic that you are interested in building, which is the schematic for a Harmonic Percolator that was owned by Steve Albini. The other is the "George Giblet" schematic, which was put together by a guy named George Giblet who circuit traced an original Harmonic Percolator. The circuit topography of both versions is essentially identical, but many components have different values, and as a result the two circuits sound very different from each other. The Harmonic Percolator is a very finicky circuit and changing the value of even a single component can make a significant difference in how it sounds. I used the George Giblet schematic as the starting point for my build, and the overall tone is much more like the George Giblet version. I don't know what would happen if you changed some of the values on an Albini-spec Harmonic Percolator to match the mods that I did here. My guess is that it would sound different, but I can't predict anything more specific than that. If you're curious how it would sound, I would encourage you to breadboard it for yourself and report back.

 

[eurobailey]

There are a couple different Harmonic Percolator schematics floating around out there. One is the "Albini-spec" schematic that you are interested in building, which is the schematic for a Harmonic Percolator that was owned by Steve Albini. The other is the "George Giblet" schematic, which was put together by a guy named George Giblet who circuit traced an original Harmonic Percolator. The circuit topography of both versions is essentially identical, but many components have different values, and as a result the two circuits sound very different from each other. The Harmonic Percolator is a very finicky circuit and changing the value of even a single component can make a significant difference in how it sounds. I used the George Giblet schematic as the starting point for my build, and the overall tone is much more like the George Giblet version. I don't know what would happen if you changed some of the values on an Albini-spec Harmonic Percolator to match the mods that I did here. My guess is that it would sound different, but I can't predict anything more specific than that. If you're curious how it would sound, I would encourage you to breadboard it for yourself and report back.

Thank you. Good advice. I will take a look at the GG version. Breadboarding sounds like a must with this one ! thanks again. Your post has led me down a rabbit hole of info haha.