BYOC 2-knob Bender kit

[Mark Hammer]

A buddy brought over a few pedals for me to take a look at yesterday.  One was a BYOC  ESV Mk II 2-Knob Tone Bender.

The unit uses a trio of OC75 transistors.  I measured them and all three had hfe readings in the 140+ range, including the one used as essentially an input buffer.  The wiring job was kind of sloppy.  From what he knew the pedal was originally assembled by some inmate program.  So, everything was in the right place, but the solder joints were somewhat sloppy.  Guess you have to start somewhere, if you're trying to learn a job skill for the outside world.

The pedal was a little on the hummy side.  Just for the heck of it, I pulled the input transistor  (all 3 are socketed)  and subbed it with a much lower (43) gain OC70 that someone had graciously sent me some years back.  I figured gain would be largely moot for an input buffer.  The change in transistor provided no audible change in the sound, but was MUCH less hummy.  The pedal is now fairly quiet when one is not playing.

So I guess the moral of the story is: save those germanium transistors that seem too low gain for Fuzz Faces, and use them for input buffers.

[antonis]

save those germanium transistors that seem too low gain for Fuzz Faces, and use them for input buffers.

Quite heretical aspect, Mark..

[Electric Warrior]

Simply biasing the first stage correctly with a 10k on the base probably would have helped, too. The 100k works well for a low leakage transistors. A leaky type like an OC75 sounds much too compressed with a 100k.