Rocktron Black Cat Moan wah - mods for you

[grolschie]

Hi guys,

I've been tweaking my Rocktron Black Cat Moan wah today, so I thought I'd share some info for those perhaps using this site's search engine later on. 

Basically, the Black Cat is very similar to the Vox 847 and Dunlop Crybaby GCB-95 circuits but with a few extra goodies (buffers, asymmetic "moan" boost, switchable sweep caps, etc), so the existing mods work this one too! With the Moan boost, the pedal can sound ok, but still not so good in normal mode. I wanted a better basic wah sound before using the boost.

Less vocal:
The 33k resistor parallel to the inductor in the other two wahs is R5 [68k] in the BC. A typical mod to give it a more vocal sound. Too much for me, so I tried a 33k resistor which was more my thing. Settled on a 39k in the end though.

Less mud in heel position:
The stock pedal is too muddy when in the heel position, so I changed R9 [390 ohm] at the emitter of Q1 to be more like the Vox (510 ohm) but only had a 560 ohm which was close enough. I might try the 510 ohm later though.

Shift the wah range:
The crappy pot really needs to be replaced. At full adjustment it doesn't quite have enough treble and doesn't quite get to 100k. Some people mod their pedals for more bass, but the BC has a a knob to switch between 3 sweep caps. I had plenty of bass options, so I swapped C5 [0.01uf] to a 0.0082uf. I could probably go a little smaller though.

Smooth out the sweep:
I replaced the stock R1 [1.5K] resistor between the base of Q1 and the inductor to a 2.0K resistor. This also helps to smooth out the response between the bass and treble.

Increase output level:
After these mods, I noticed that the volume when switched on (not using the boost) was lower than bypass mode, so I swapped R15 [68k] to 39k. On more simple circuits, this is the input resistor, but on the BC there is a buffer before this.


I hope that this helps somebody. 

Many thanks go out to those who posted Vox or CryBaby mods on their websites (e.g. diyguitarist, Erik Hansen, S. Castledine, Andreas Möller, etc) and to Bajaman.