Chuck D. Bones
Circuit Wizard
It's worthwhile to read the backstory of this pedal on the Aclam website.
I breadboarded this baby in accordance with the Beatle Juice build docs. Ok, I made a couple of substitutions. Q1 & Q2 are 2N2222A on my breadboard and Q3 is a BC549C. I used Russian D2E diodes for D1 & D2. Based on the Vf readings on the schematic below, they should have a similar V/I curve to the OA200 diodes. I prefer A-taper for the BIAS pot. I didn't have another B10K handy, so I used B25K for the VOLUME pot. I subbed 470nF for C8 because 10uF is way overkill. I understand why Vox would have used 10uF everywhere, it's convenient from an inventory point of view.
This thing sounds great. Dirty, but not too dirty. There's a sweet spot with BIAS around noon (on an A-taper pot). It's a low-to-medium gain OD. I think it's a bit bottom-heavy with Humbuckers. To cure that, I added an A500K TIGHT pot along with a 4.7nF cap in series with the input. I also tried an MP38A Ge tranny in place of Q2. Not a huge difference, but I like it. To accommodate the Ge tranny's bias requirements, I increased R7 to 6.8K and the BIAS pot to A25K. I might try one or two other component value changes.
Knobs (L-R): VOLUME - TONE - BIAS
I breadboarded this baby in accordance with the Beatle Juice build docs. Ok, I made a couple of substitutions. Q1 & Q2 are 2N2222A on my breadboard and Q3 is a BC549C. I used Russian D2E diodes for D1 & D2. Based on the Vf readings on the schematic below, they should have a similar V/I curve to the OA200 diodes. I prefer A-taper for the BIAS pot. I didn't have another B10K handy, so I used B25K for the VOLUME pot. I subbed 470nF for C8 because 10uF is way overkill. I understand why Vox would have used 10uF everywhere, it's convenient from an inventory point of view.
This thing sounds great. Dirty, but not too dirty. There's a sweet spot with BIAS around noon (on an A-taper pot). It's a low-to-medium gain OD. I think it's a bit bottom-heavy with Humbuckers. To cure that, I added an A500K TIGHT pot along with a 4.7nF cap in series with the input. I also tried an MP38A Ge tranny in place of Q2. Not a huge difference, but I like it. To accommodate the Ge tranny's bias requirements, I increased R7 to 6.8K and the BIAS pot to A25K. I might try one or two other component value changes.
Knobs (L-R): VOLUME - TONE - BIAS
