Wednesday, July 22, 2015
Ibanez Dirt Box
Here's a rare one from the 70s by Ibanez. It was originally marketed as the OD-850 Overdrive II (not to be confused with the OD-855). But since the nature of this pedal is more distortion/fuzz territory, it wasn't a great name and it was changed to the Dirt Box. Whatever you want to call it, the circuit is essentially a Distortion +/DOD 250/Ross Distortion with a dual op-amp and a Tube Screamer-like tone control. The 220n capacitor coming off lug 2 of the Tone pot was originally a tantalum cap, but like the Tube Screamer, using a film cap should give better response. The sound is apparently similar to the op-amp version of the old EHX Muff Fuzz (the one that plugged directly into your guitar, not the BMP).
The bottom right 10k resistor's right leg (row N, column P) should connect to the left leg of the 10k above it (row M, column M), not the right leg (row M, column P). Otherwise, they don't form a voltage divider.
ReplyDeleteWith that change, the circuit works.
Not very responsive to playing dynamics or the guitar's volume knob, but it does sound good. I think I prefer the Ge diodes to the Si ones.