Whisker Biscuit Mods, Anyone?

[Freekmagnet]

I just built up an ROG Whisker Biscuit in a box with an extra switch hole and room for a SPDT switch. Anyone have any mod suggestions? I tried adding one of the optional 47pf that would supposedly change the sound, but I didn't hear any noticeable difference.

[JustinFun]

The obvious thing would be to implement any one of the many BMP tone control mods.

The 'body' control found about halfway down the page here: http://www.beavisaudio.com/techpages/BigMuffToneControl/ would be a good choice, or you could just add a switch to bypass the tonestack altogether.

[jmasciswannabe]

You could tack a starve knob on there. Might get you a cool gate going on, but not sure. The biscuit is noisy so this would actually be useful! Just run a 10k potentiometer between the ac in and 9v in on board.

[midwayfair]

Schem (always post the schematic so people know what you're looking at): http://home-wrecker.com/whisker.html

You can add a gain control between stages 1 and 2.

I have a switch on mine that swaps out the 4.7n in the tone stack with a huge 220nF cap. There's not much difference at lower settings, but the clockwise settings have far more bass. This lets you get a treblier sound without as much bass loss and reduces the scoop as you go up on the tone. Output is also increased ... a lot.

[Freekmagnet]

Cool. Thanks guys - these are all great ideas! The tonestack bypass sounds easiest to impliment, however changing the cap sounds really cool. I think I might have a few .1u caps laying around, so maybe I'll try wiring switch to add one in parallel with the 4.7nf cap.

[thehallofshields]

I second  the gain pot idea. I figured RoG chose not to add one because of the Bazz Fuzz's tendency to gate. In my builds I've added a 1M resistor in parallel with the diode to help. A 1k resistor between Q2's emitter and ground helped noise in my build as well.

[Mark Hammer]

T'wer I, I'd implement a "shift" switch for the tonestack. 

Stock, the circuit provides a pretty substantial mid-scoop.  The 33k/4n7 pair roll off below 1026hz (albeit at 6db/octave), and the 33k/33n pair roll off above 146hz (same slope).  The degree of midscoop, and hi-lo balance can be modified by tweaking any of those component values.

My inclination would be to vary the values of the two caps, using either a DPDT or a 3-position DPDT toggle.  Here's an example.

Our 3-position toggle is set up like this:

---1n2 cap----A---1M---B---------C
                        D---------E---1M---F---15n---
                        |_______________|

Replace the existing 33nf cap on the bass side with 18nf.  Straddle two lugs on each set of contacts on the toggle with a 1M resistor (to bleed off the cap when not in use, so as to prevent popping).

From the outside lugs on each side where the 1M resistor is, run a cap to one side of the existing 4n7 and (new) 18n caps.
Run a lead from the other end of the caps on the circuit board to terminals B and E.
Run a wire from lug D to F.

In the middle switch position, your tone circuit will be essentially using an 18n cap for the bass side (rolloff above 268hz), and the stock 4n7 for the treble side.
Connecting B-C and E-F (bridging the 1M resistor) adds in 15n and restores the 33n stock value on the bass side, while doing nothing on the treble side.
Connecting A-B and D-E adds 1n2 to the existing 4n7 cap, dropping the treble rolloff point down to 817hz (you could also use 1n5 instead of 1n2, which would drop it down to 778hz).  The wire link between D and F also brings in the added 15n cap on the bass side.

What you end up with is
1) Stock on one side position
2) Same treble but more lower mids in the middle position
3)Stock bottom but more upper mids in other side position

The existing tone pot still allows for adjusting the balance between top and bottom to taste/needs.  That's a bigger palette than you might think.

[thehallofshields]

Wow Mark. Always such practical advise. How do you come up with this nifty stuff?

[Mark Hammer]

40 years of practice, 39 of them mistakes.