After building about ten circuits with mostly scavenged parts, I decided it was time to treat myself. I ordered the best quality stuff I could from SmallBear - 1% metal resistors, 10% vishay electrolytics, Mallory 150 cap, Carling switch, NOS BC-108 transistors. Even with going all out, total cost for this build was only $25. The only scavenged parts were the jacks and the enclosure, which was my loved-to-death DOD Overdrive Preamp. The schematic was the 1970 Silicon FF version from General Guitar Gadgets; the layout was modified from a FF clone called the Silli-Face (runoffgroove.com).
Starting to get assembled. There are a few modifications. First, a 10k trim pot instead of the 8k2 resistor. This allows the bias of Q2 to be dialed in exactly and altered to taste. Second, a Neg. Log taper pot for the fuzz control, which helps smooth out the pot's rotation. Third, a 100ohm resistor between the emitter of Q1 and ground. This helps control the gain of Q1 and helps mellow the fuzz a bit. Finally, a 10pf cap from collector to base on Q2 softens the treble and filters out radio interference. The perf board happened to fit almost perfectly in the enclosure. After sanding a bit off the sides, I could simply wedge it into place instead of worrying about mounting it.
Finished! I set the voltage on Q2 to 4.5v and tweaked from there (about 5v sounded good to me, though I got some nice Maestro FZ sounds at around 6.5). I ordered 4 transistors so I could match them (both are ~350hfe). The fuzz control is still useless as it gets too muddy when turned down, but it's easy to alter the fuzz level with guitar volume. It would be much better to have access to the bias trimpot to alter gain, and I may try this on a future project. Overall, I'm very pleased with the sound. The bass can be overpowering, but I can always tweak the cap values later. There's also plenty of output available, with unity at around 12:00.
For the clip, I'm using a '67 Duo-sonic with my Vox AD15 set to a Twin sound. You can hear the extreme bass near the beginning - this only happens with the guitar volume on max and turning it down even 5% evens out the response. All the variations in gain were done with the volume knob.
[stream]http://bestnetworx.com/uploader/files/6 ... emoMP3.mp3[/stream]
