Projectile Overdrive

[ianmarks]

A fairly easy build. Biased the jfets around 4.65 with the trims. The high control gets nasty when cranked along with the gain. Like that harsh octave clang kind of texture. I thought it might be a mishap on my part but I verified the same behavior through a bedroom videos youtube vid. Kind of a dirty OD as compared to smooth and worth a build if that is your thing (definitely mine, ha!) Per usual homage to the original graphic design. I see where there is a MK2 that adds some versatility with an extra preset ability. I'd be more interested in what the extra gain stage might do. I am surprised that was included as it has a good amount of gain to begin with.

 

[schnerf]

I bought the MK2 -- it's not a preset but just has two, duplicate circuits and a toggle. I like it so much that I'm building this one. Question: how did you set your internal trim pots? If there's not a known value for each, can you give a hint as to what each one does?

 

[ianmarks]

Pretty sure the trims bias the individual jfets and rule of thumb is to bias them at half supply. Start there and if you really want to get into fine tuning, audio probe after the selected jfet and adjust to taste. In my experience I have seen folks bias them a little hotter than half. Enjoy the build!