light bass overdrive

[Tomcat706]

Hey all,
I am looking for a little grit in my signal, right now I'm using a BYOC confidence boost, but the volume is uncontrollable and hard to manage on stage. I'm looking at the RoG peppermill and doubling the input and output caps. Is this right, any other suggestions?
P.S. Merry Christmas

[jafo]

That should work just fine; in fact, something like that was my first build. Doubling the caps halves the cutoff freq, so you're on the right track there. I'd strongly suggest that you socket both of the FETS (at least the JFET) and try several. It's worth noticing that the Rs (source-ground resistor) of the J201 is 1k, which is pretty close to the average optimal value for a 201 to have a more triode-like response per the Fetzer Valve, although you'll want to either omit the cap that bypasses it or make it smaller for the full effect -- which will darken the tone appreciably (since it's a high-pass filter acting as a treble booster).

If you're up to some experimentation, you can get a more grit with clipping diodes after the JFET's drain cap; you could connect them straight to ground for a harder sound, or to the JFET's gate for a much softer sound. I suggest maybe a red LED or a silicon or both, each oriented differently (so that both halves of the wave get clipped). If you use different diodes, you'll get asymmetrical distortion, which a lot of us find more pleasant (symmetrical waveforms have no even-order harmonics). You could even try clipping just one half of the wave.

Still, the Bazz Fuss is a much easier build (since it uses a BJT instead of FETs) and also sounds great. It's a one-transistor gain stage with a single diode fed back to soft clip one half of the waveform. Use a red or orange LED for less distortion -- either it has a higher transfer voltage than a silicon or germanium, which means less clipping. Even better, you could just socket the diodes and try a few types until you find what you like best.

[Tomcat706]

Thanks man,
I apprectiate the help and the info, I am going to try breadboarding the bazz fuss today and oring the parts for the peppermill.

[matt239]

For even "lighter" clipping (as in not too fuzzy)
- You could try an LED, a germanium (like 1N34,) & a small resistor, (250 Ohm?) all in series as your clipping diode string.
- You might want to consider NOT increasing the value of the input cap; let it trim some bass, then include a complimentary bass boost AFTER your clipping section.

(Too much bass content into the clipper can result in a rough, fuzzy, grungy distortion, - a common problem in bass Overdrives..)

[ubersam]

(Too much bass content into the clipper can result in a rough, fuzzy, grungy distortion, - a common problem in bass Overdrives..)

I ran into that issue when i was experimenting with distortion/overdrive for bass. One thing that really improved things was adding a clean blend circuit, kinda like how it is done in the Sparkle Drive. That way you can mix in the clean signal with the clipped signal. You can play around with the low freq. roll-off of the clipping circuit so that it only clips frequencies above, say, 200Hz, for example.

[matt239]

adding a clean blend circuit, kinda like how it is done in the Sparkle Drive. That way you can mix in the clean signal with the clipped signal. You can play around with the low freq. roll-off of the clipping circuit so that it only clips frequencies above, say, 200Hz, for example.

+1!
Just a mix doesn't help enough though; if you blend in enough full band OD to know it's there, it's too fuzzy. The boss pedal has this problem..
Cutting bass, then boosting it, or splitting bands, & clipping the high band more, low band less, & softer..
See Jack Orman's "tone clipping" article @ AMZ..

I think it might even be good to make the shift/split freq. more like 500 or 700Hz. - 700Hz would be like tube screamer for top, & you could have higher threshold & softer for bottom; LED/1N34/250 Ohm R..
Or 1k Ohm R.. experiment. (Or LED/1N34/1N34/250 Ohm R.. etc. ..) (Or split freq 3 ways!! )

But in the short term, for the circuits you said you were going to build, just try NOT increasing the input cap, & make the post-clipping, filtering/tone control, boost bass. This should help a lot..

[jafo]

+1 on the split/blend idea  -- that'll add a great deal of tonal and textural flexibility. Maybe you could build a Peppermill will some diode fun, but also take a tap off the MOSFET as the clean signal?

Pedal projects always seem to get out of hand... it's so easy to add just one more little tweak.

[Tomcat706]

To do the split/blend, what do I do? Do I run to lines off the in, one to a low value cap to the circuit, and one to a higher value cap past the OD? If so how do I blend the signals? If not could someone enlighten me?

[jafo]

Just take a line from the cap following the MOSFET, and send it to a volume control. The MOSFET stage is basically a buffer, and leads into the JFET stage; the cap is there to remove any DC component. (You could also just take the plain signal from the input, but I think that taking it from the MOSFET buffer will mix better with the distorted signal.)

ASCII graphics, alas...

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                    JFET stage - RC network - Volume pot
                   /                                    \
In - MOSFET - cap <                                      > Out
                   \                                    /
                    -------------Volume pot-------------