68 tele with a 1-off mystery fuzz circuit!

[ghostsauce]

Where's this thing getting it's fuzz from, anyways? Without a second transistor or diodes, shouldn't it be only a boost like aron was saying? I first thought maybe it was the bias of the 2n2925, but I'd think it would sound gated if it just wasn't getting enough voltage, and the 5088 is just purely clean.

[PRR]

> it is not a proper, text-book Baxandall

I don't see any relation to a Bax or James tone-control.

It is a Twin-Tee. You find Twin-Ts in older Gibsons, sometimes sprinkled like salt, rarely variable.

Bass passes through R1 R2.

Treble passes through C2 C3. (C1 is just a coupling cap and may have nothing to do with tone shape.)

It can be sensitive to source and load impedance.

Twin Ts usually give a mid-range dip, though many alignments are possible, and with heavy loading a small mid-boost is possible.

Mid-dip is characteristic of the classic Fender X-Face amplifiers for many settings of the B M and T knobs.

However this Twin-T is inserted in the feedback path? Then mid-dip becomes mid-cut, all is backward. If the forward amplifier had infinite gain, you could study the Twin-T abstractly. But 1-transistor is far from infinite gain, and you have to consider them (and R4 and other stuff) together.

I can well believe this wasn't "designed", but "just happened". Schemes like this are incredibly painful to design by hand. It was done for RADAR and some Bell Labs projects, but they had 'computers' (low-pay workers with adding machines and log tables).

[slashandburn]

Thanks Paul. I'm really looking forward to getting to play with this and try to get my head around how it works.

[ghostsauce]

Very neat, PRR, thanks. Any suggestions on where else to place the twin T for different effects? Adding a mid boost might be nice.. maybe even as a second tone control or something funky like that.

[Hatredman]

> it is not a proper, text-book Baxandall
I don't see any relation to a Bax or James tone-control.
It is a Twin-Tee. You find Twin-Ts in older Gibsons, sometimes sprinkled like salt, rarely variable.

Yes, you're right. I didn't know how to call it, so as it resembles a Bax a tiny bit I called it "Bax-ish". Never knew its proper name.

[ghostsauce]

So, I'm looking at R5 (470K) right now and wondering. Is this the input impedance? If so, putting it to 1M would probably be more useable and roll off less highs as you adjust the guitar volume, right?

EDIT: hmm, after doing a little more research it may not mean anything on it's own.

[PRR]

Not real sure which schematic you are looking at.

The input is not R5. That is primarily DC bias. Also R5 is levered-down by transistor voltage gain to present a lower impedance to the guitar.

It all gets even messier with the Twin-Tee wrapped around.

Leave it alone for now. The circuit apparently DID work. Pre-thinking is folly. It is not faultless, and maybe is not a sound you want all the time, but it promises to be good for something.

[ghostsauce]

Gotcha, thanks for the info.