Tonebender MK II bias control

[Freddy205]

Hi there, I was just wondering how the bias control on the retroman lola ( A Tonebender MKII clone - http://www.retroman-music.com/prod02.htm ) is implemented. Would it just be a 50k or so pot in series with the input? Or is it something more complex? I just built one of these babies with a few component value switches and I'm very pleased with it, I'm just looking for more mods and improvements to make to an already brilliant circuit even better.

Also one other question. I run this thing (positive ground PNP) off of my regular 9V wall wart. I've just flipped the leads around on the DC adaptor jack around so that the circuit receives -9V instead of +9V. This means that I can run the circuit from the same dc block as the rest of my pedal board. I was just wondering if this is wrong/damaging towards the circuit in any way?

[petemoore]

short workable answer is:
 IF you are using PNP transistors use Pos Gnd. running a Pos Gnd circuit on neg Gnd supply is basically a no no.

[cd]

Also one other question. I run this thing (positive ground PNP) off of my regular 9V wall wart. I've just flipped the leads around on the DC adaptor jack around so that the circuit receives -9V instead of +9V. This means that I can run the circuit from the same dc block as the rest of my pedal board. I was just wondering if this is wrong/damaging towards the circuit in any way?

Yes.  Think of it this way: you flipped the jack around so that the - goes to power the effect, and the + goes to ground.  Now try to put another effect that has a negative ground (like a BOSS pedal) in parallel (run it off the same supply).  The BOSS pedal uses the + to power the effect, and runs the - to ground.  But wait: with the other pedal, the + goes to ground, so you've just grounded the power to your BOSS pedal.  And the BOSS pedal uses a - ground... so you've just grounded the power to your other pedal.

You can run ALL negative ground pedals from one flipped over adapter, then run all your positive ground pedals from another.  Mixed together, they won't work.