Oy.
I built the OS using 2N5458's, 4558 and a 1N4148 diode, and been playing around with it a bit for the past few days. I certainly like the way it pushes my Tracer MA-10 into better distortion (tho kinda noisy) and it has good sustain. Very nice for that simple a project.
I liked the "stock" version, so I thought I'd see what Mark Hammer's variation was like. I found it more subtle, more "even" rather, but I got a problem with the output module (everything after the 10k Level pot).
At max level, the sound is almost cut, all I get is this splatter of distortion when I pick the string very hard. I traced the circuit with a probe, and the signal gets in the second half of the 4558 ok, but it comes out the way I've described at its output (I also observed the same effect happening at the Vcc connection of the 390K and 330K resistors -- should I hear a signal from there at all?). If I back off the level to around half, the sound is clear, but it doesn't push my amp's disortion nearly as far as taking my output right out of the level pot.
I checked my ground connections, as the Dr. Quack and Pulsar I built had the same problem, which went away when I reconnected that lose wire to ground. I changed the opamp to another 4558, no difference. I read that a Si diode would eat up more signal, but mine works, tho I just clicked that that might cause my splattering? So, I'm gonna keep looking for the bug, if anyone has any input, I'd appreciate.
Ciao.
*whistles the Gilligan's Island Theme, curses and turns the tv off*
Edit: Changing the diode to a 1N60 didn't fix the problem.
Hard to wrap my head around what might cause that particular problem, but one thing it certainly isn't is the diode choice. Are you sure the electrolytic caps in the second stage are oriented correctly? I've run into a few instances where I had misoriented + and - leads and the end result was something where it was quiet until I picked hard, whereupon it went "splat".