For a great bass tonestack, a la BMP, (using the schematic available on this site) , change R17 & 23 to anywhere between 5.6K – 15K. Vary & tweak this # to taste, of course. I started with 5.6Ks.

Change C11 to .22uf. Then, change C10 to anywhere from .0068 – .01uf. An .0086uf cap here seems pretty good for me so far.

Raising R17 & R23 in tandem seems to yield more ‘edge’ to the bass sound – lowering down to 5.6K resistors takes off edge, & makes for a round, lowpass bass tone, interactive w the TONE pot, as you’ll notice. This change is very interactive w tone pot’s position.

I use a 10K, dual-gang pot in series w the 5.6K resistors, & this gives me a neatly variable ‘edge’ control for this tonestack as adapted to bass.

For the TONE pot, use the usual 100K/L one, but, place a 47K resistor between either end lug, & where you connect the tonepot to the normal spots on the BMP circuit.

Since I use this tonestack as an isolated bass tone control, I found that placing a very simple, 1 FET (or 1 MOSFET) low-gain, low distortion, clean boost preamp here, with a large electrolytic cap output – like, 10uf – 100uf, compensates for the signal loss the tonestack can produce. (or, just turn your bass amp up)

I’m a bassist, and I really want to do a Big Muff. But this is a guitar version. Have you any idea for changing this circuit to make a Big Muff Bass version ? I think I must change some capacitors (and maybe some resistors too), but I don’t have any idea on which I have to use.

Any idea ?

I bought them and they’re arriving but in other site I see the pot are 10k!

Taking off from the fact that the BMP tone control was bass friendly to begin with,I wnet looking for a clean bass tone control, minus the distortion. &, sure ’nuff, I ‘ve tweaked some good mods for adding a clean, tuneable, midscoop-to-pure lows bass tone control onto my bass. Doesn’t even need any compensating clean boost actually – I just turn up the amp or mixer volume.

Just tweak biases, caps, tonestack, & diode types by ear, & to individual taste. You can come up w a very individualized pedal sound w this one.

There is, (to my ear,anyway) a very distinct difference in sound between 1N914 & 1N4148 diodes as clippers. From my A/B ing, the 4148s are dirtier, & edgier, & closer to the original BMP. There seems to be more intermodulation FX & intermod-type sonic artifacts w them. Harsher.

1N914s sound cleaner, more ’rounded’. I ‘hear’ a bit more 2nd harmonic oriented, tubelike roundness w their use, a cleaner report. In just about any clipping circuit – trannie or op amp.

While 1N34a’s yield a compressed sound w higher drive & gain, they also can carry a neat, uniquely characteristic static-y ’spike’ in many builds – when you don’t drive them too hard. The Univox Superfuzz, Fender Blender, & (various) 1N34a laden Octavia-type builds sound this way.

It’s only when you really push them that you come up w those very compressed , smoothed out ,less clipped sounds.