Perc / Jerc

[PMowdes]

Hi all

I've got a few issues with the perc / jerc build  

http://guitar-fx-layouts.42897.x6.nabble.com/Harmonic-Perk-amp-Jerk-SMD-TH-hybrid-td31209.html

Both effects kinda work but.

The perc side is very quiet.  It sounds right, harsh, glassy but the volume just isn't there.  I used an AC128 (I can't remember the hfe or leakage)  

Am I right in thinking that in this case the higher the hfe of the pnp trannie the lower the output volume??

Second issue is the jerc.  

This side is loud.  But it only works with one set of diodes (the Ge ones I think) or if you thrash the guitar really hard, but the signal breaks up and then cuts off long before it should.  What could be causing this??  mis-biased trannies??  And if so how to you bias this thing, it aint very straight forward.

Any help greatly received

Cheers

Phil

[induction]

PMowdes wrote

The perc side is very quiet.  It sounds right, harsh, glassy but the volume just isn't there.  I used an AC128 (I can't remember the hfe or leakage)  

Am I right in thinking that in this case the higher the hfe of the pnp trannie the lower the output volume??

Legend has it that the PNP should be pretty low hfe (somewhere between 40 and 60 is pretty common), and your AC128 is probably in the 200 range. I suspect the difference would be in the tone more than the volume, though. It should be loud as hell without the diodes, so if that's not the case then I suspect a build problem here.

Second issue is the jerc.  

This side is loud.  But it only works with one set of diodes (the Ge ones I think) or if you thrash the guitar really hard, but the signal breaks up and then cuts off long before it should.  What could be causing this??  mis-biased trannies??  And if so how to you bias this thing, it aint very straight forward.

This circuit should not need to be manually biased. In any case, the diodes come after the output cap, so the signal seen by the diodes should be zero-biased, regardless of the biasing in the gain section. If it works with one set of diodes, but not another, then the chances are really high that you have another build problem. How does it perform with no diodes?

If you post photos, I'll take a look when I get a chance.

[PMowdes]

Hey Induction

Again thanks for the reply, as I mentioned in the thread in the contributions section I made a pcb of this, my fat fingers just don't get on with the smd's I'm afraid.

I don't have the pedal or the pcb to hand but here's what I do have (I don't have a pic of the reverse with me





I basically borrowed the pepperspray schematic and doubled it up with a dpdt switching the input & output.  I subbed in the various values from your smd build

I wonder if I have the switching wired in wrong or something off board.