Harmonic Perculator

[km-r]

what does this effect do anyway?

[tcobretti]

FUZZ!

[theblackman]

NONONO!

it "percolates" harmonics. 

anyway watch the video clip that was in an earlier post. 

[mattpocket]

Distortion/Fuzz.

Lots of highs!

[George Giblet]

>Hi I am about to attempt this build, when biasing the transistors, should i just be aiming for 4.5v at the collector of the NPN? (Also at the emitter of the PNP)?

I'd say no, this circuit is different to "normal" circuits.  Two main reasons:  the emitter voltage for the top transistor isn't zero volts so an equivalent to mid supply/4.5V would be (emitter voltage + 9V)/2, and, even that won't work because the transistors are deliberately biased with low emitter to collector voltages.

[mac]

The sound is unique, it filters harmonics according to the original ad.

Something I'm going to do when I have some free time is to invert the circuit. That is, the input to a Si npn low gain, around 50-70 like a 2n2369, and then a higher gain Ge pnp, gain near 150-200. The output from the pnp collector. Positive ground, or if there is no oscillations negative ground.
Just for fun.

mac

[theblackman]

i built this yesterday, it has a really awesome grinding sound. I can't say it's really unique sounding though. I was unable to get the whistling sounds that albini gets in that video from earlier, but i get some oscillation when the harmonics are turns fully clockwise (this unit tends to be fuzzier turning harmonics counter clock wise right?).

i think i'm having problem finding that sweet spot, but i have noticed there are a range of  useful sounds when biasing with pots, and the harmonics really do pop out on this thing! i wish i had some kind of recording device so that i could post some of the mayhem i have been creating with this thing!

Anyway, I haven't put any diodes in it yet, i am thinking of making a toggle switch to choose between two sets of diodes, any suggestions?

[mac]

I think that a rotary switch could do it.
Some ideas:
ge+1k, ge (the standard)
si+ge, si (more volume)
ge+schottky 1n5819 ,ge
none

mac

[foxfire]

i built tim's harmonic jerkutator a month or so ago. i didn't add the diodes because of the volume drop. i think it was only the second pedal i had made so i wasn't all that sure of what i was doing not that i am now. anyway i really like it because it is so different than my other fuzzes. i like the turn the fuzz up and the volume to around 10o'clock and use it on top of another fuzz or the amps distortion. it gives my "that guitar sounds like a bass" a nice nasally type of sound for when i want to stand out a bit.

i have only been sneeking peeks at this thread so i guess i should go back and get caught up but, is this going to end with the ultimate hamonic perulator layout/schematic?

[mac]

I'm sure that there are some layouts and schems in the gallery. Most of what was discussed here is the effect of diodes and transistors bias for the Hermida and Barge versions. My contribution was the all Ge Hermida version, which IMHO sounds a lot better than the Ge-Si one.
Since we talked about breadboarding first using trimpots for the 4 bias resistors to find the sweet spots, all layouts in the gallery can be used. Just replace the trimpots values with the nearest resitors.
Adding a switch to change diodes is easy.

mac

[foxfire]

i'm gonna jump into this when i get back from my little "camping" trip. the super hp...

[mattpocket]

I still havent finished mine! haha

Did anyone find the Si-Ge hermida version to be very harsh and trebley? Mine is. I placed a cap across the diodes to smooth that out, and added a tone control, but it cuts a lot of volume when you use it. Is there a way to boost the volume before the tonestack? Some arrangement with diodes maybe?

Matt

[theblackman]

what diodes did you use? I haven't put any in mine yet and all i get is a really thick loud bombastic fuzz! anyway to boost the volume
use an si+ge, ge combination as in mac's earlier post.

[mattpocket]

You mean add a Si to make assymetric clipping?

I brought a load of different diodes, and just tried them out. The Ge's I used fattened up the sound bass wise, but they farted a littlen and seemed to gate the sound slightly. I tried a fair few different Si's, and I finally settled on 1n914 I think, but dont quote me on that. They were a pretty similar sound to 1n4148, but ever so slighty smoother, without farting out. You can also try putting a cap in parallel with the diodes to smooth it out, it made mine a lot more useable, with a more fuzzy type of response, but still retaining that harmonic grit sound.

Hope it helps!

Matt

[theblackman]

yeah an si and ge in series assymetric with a si. if you use more diodes this allows for more output this is explained on the general mods page i think?

[mac]

Maybe lowering the PNP collector resistor like the barge version may help to boost volume, somewhere between 100k and 22k.

mac

[theblackman]

i put the germanium diodes on last night and i think it really does sound like the harmonic percolator in the albini clip. sounds a whole lot more trashy than without the diodes and does seem to accentuate the harmonics further. I think I'm going to leave it just like this!