Stupidly Wonderful Tone Control quick question

[solarplexus]

Does this tone control suck alot of volume in the pedal compared to the BMP tone stack??

Reason I ask :

I have built a peppermill with two diodes for clipping right before the volume (which works perfectly) BUT it does suck some of the volume available, and I would like to add a simple tone control but don't want to compromise the output...

so... what's the verdict? ??


Thanks for your help!

Matt

[foxfire]

i just spent about 30min. looking in to the swtc and the bmp tone stack. from what i could tell from all the posts about it, it doesn't suck much if any volume. i was gonna use the bmp tone stack for my muff fuzz, but i think i'm gonna go with the swtc.

[Mark Hammer]

ANY circuit modification that bleeds signal to ground will reduce signal level.  The question is "Enough to make a big difference, or small enough that I won't notice?".  I labelled this thing "wonderful" because it was as invisible a passive tone control (in terms of signal loss) as I've ever found.

[solarplexus]

Well that's exactly what I need then.  There is plenty of volume still available in the peppermill with the diodes, but I wanted the volume drop as minimal as possible. 

Would using 4 diodes instead of 2 drop the volume by half again or it goes like 1/2, 1/4th, 1/8th, 1/16th?

Thanks Mark!

[Mark Hammer]

Used in that manner, the diodes will set a ceiling on the signal level possible.  A pair of equal-value back-to-back diodes will set a clipping threshold of whatever their forward voltage is in each direction.  So, if you measure their forward voltage and it's, say, 280mv (Ge type), then if the negative or positive peaks exceed that voltage, the diodes will start to conduct to ground, such that the signal can't get any "bigger" than that voltage.  Sticking diodes in series means that their respective forward voltages will be added up.  Stick another pair of diodes with a 280mv forward voltage in series, and conduction will not take place until you reach 560mv.  So, highest potential output level will occur with more diodes in series and with diodes having higher forward voltages.  All conduction-speed differences aside, a red LED will have approximately the same clipping threshold as 6-7 germanium diodes in series, and about the same threshold as 3 silicon diodes in series.

Given what you are trying to do, here is the Peppermill I would suggest:
1) Stick 2 1N914 or 1N4148 diodes in series.  Do it again.  Stick those two pairs (back to back) between the output side of the .047uf cap and ground.  That won't get you tons of clipping but will get some bite when you dig in.
2) Replace the 8k2 fixed resistor with a 1k fixed resistor and 10k linear pot in series.  The 1k goes from the .047 cap to one outside lug of the 10k pot.  The other outside lug of the 10k pot goes to your 100k volume pot.
3) Run a .015-.022uf cap from the wiper of that pot to ground.

As the wiper is moved towards the diode side, you will get closer to full bandwidth.  As the wiper gets moved to the volume pot side, the high end rolloff will move down to 964hz (with .015uf) or 658hz (with .022uf).  The 1k resistor sets an upper limit on how high up the rolloff can go.  That setup won't get you the EQ of your dreams, but it will "soften" the edge of whatever clipping you get, all without changing your output level much.

Let us know how well it works, and we'll take it from there.

[solarplexus]

Thanks Mark!  I'll do that tonight and report the results!