I have a question for gaussmarkov re: the 8V on Q3 of my BMP. Can you explain how this biasing yields the great asymmetrical clipping you speak of?

It is a very overdriveable sounding Muff. that’s for sure. I was just playing some power chords w it, & w some added 3 way EQ on my mixer, it really can yield the hardest-hitting sounds of a huge, driven stack when set right. Even @ 9 o’clock Sustain settings.

How can I go about duplicating this setup (voltage, etc) when breadboarding a muff duplicate mod?

(wow, almost yr ago – sorry ; I haven;t visited here that much this past year)

The 10K/L dual gang pots just increase the resistors that go to either end lug of the standard 100K BMP tonestack pot. So, the 5.6Ks & each of the lug pairs (2 & 3) on the dual gang are just in series w the 5.6Ks

You’re altering the tonestack’s resistors 2 @ a time – equally, in tandem, using one control.

I’ve found a neat tonestack for my Jack Casady bass as well, using the 500 oh,. I bridge a 330 pf cap across the circuit, placing a 56K resistor coming off either end of the 330 pf cap. The , I run each side (lugs 2 & 3A & 2 & 3B) of a 100K dual gang pot, w the 2 sides of the dual gang (meaning lug 2A & 1B) connecting at a midpoint.

This middle point goes to a .15 to .18 cap, which in turn is sent to ground w a 5K/A pot. This pot acts to bring back in (or take out) mids. Rotating the 100K dual pot will give profound changes in bass tone, ranging from pure low end bass to treble laden highpass sounds & everything in between. Using the Casady Bass’ 500 ohm setting, this circuit makes for a way to imitate lots of bass types.

You might have to tweak the values to conform to altering your own type of bass’s sound.

I love the idea for your tonestack, but I’m having a hard time visualizing it. Where does the dual gang pot and the usual tone pot go in relation to the circuit?

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.