Big Muff Black Russian - No "clipping" when tone pot is at 0

[arma61]

Hi guys


so I've put together a BM as per subject for a bassist, it seems this version is loved by bassist, isn't it?
It looks like it's working fine except for the totally absence of clipping when tone pot is at 0, so turned to the bass side. I've taken some pictures of the waveform

Schematic from GGG
http://www.generalguitargadgets.com/pdf/ggg_bmp_rusb_sc.pdf


Pot at 100%


Pot at 50%


Pot at 0%


As you can see at 100% signal looks like the tipical BM distorted waveform, at 50% volume decrease a lot, still there is some distortion, but at 0 what I get is a good increase in volume and distortion/clipping is gone, almost sinewave, is this common/right? or some troubleshooting is needed here

Thanks
Armando

[Seljer]

Yes. thats normal.

When you turn the tone fully to the bass side it's almost completely filtering out all the harmonics, leaving you only with the fundamental so it looks relatively sine wave-ish. Depends on the frequency,  some notes higher up it almost looks like a perfect triangle wave.

[arma61]

Thanks Simon for reply, I can now go on and finish it  !!

Thanks again!
Armando

[PRR]

> ...absence of clipping when tone pot is at 0

What frequency are you putting in?

I wonder if you used 1KHz.

Tone at minimum treble is a 800Hz low-pass. A 1KHz input's clipping throws harmonics at 2KHz and 3KHz (and up). And of course a 800Hz low-pass will cut those harmonics way down.

> loved by bassist, isn't it?

Bass runs 41Hz up to several hundred Hz. Usually the fundamentals are below 160hz-200Hz to avoid conflict with the guitar (82hz up, but a guitarist working with a bass usually works in the higher octaves).

So try 50hz or 100Hz input. 100Hz symmetrically clipped will throw 200Hz, 300Hz, 400Hz, 500Hz...... several harmonics which will pass through a 800Hz low-pass. If clip is symmetric, you get 300Hz 500Hz 700Hz and a little 900Hz--- a nice "phatt buzz" on a bass note.

[arma61]

thanks Paul,

close to 1k, about 740.00 Hz using R.G. Keen Fake guitar oscillator!

[PRR]

> about 740.00 Hz

That's upper-Soprano, and pretty good for lead guitar solos.

Bass tunes 41hz to 98Hz (more or less).

You can work an octave or so up the frets, say 200-300Hz.

740Hz is well beyond bass fundamentals, and perhaps not appropriate for bass fuzz tests.

> R.G. Keen Fake guitar oscillator!

Per R.G.'s notes, the pitch can be shifted by changing C1 C2 C3 all the same ratio. 10:1 bigger is 10 times lower or 74Hz, about the open D2 string. 5:1 (actually 4.7:1, it makes the cap numbers easy) gives 157Hz, about 8 frets up the high G2 string, where a bassist might solo.



You can just tack these big values across the existing C1 C2 C3. Pitch will be a few semitones lower, still well inside bass range.