Vintage Maestro FZ-1s Fuzz Tone

[VintageGear]

As you all might know by now, I am a huge Maestro fan. After the great help I got on reviving my phaser, I am once again relying on your expertise. The sustain of my FZ-1s (3 knobs, awesome simple decal) is pathetic. The sound dies out in a sine-wave fashion. SUSSSSTAIN..tain..tain.. gone. Bit hard to describe.

Circuit: http://s1318.photobucket.com/user/jrwinder635/media/4-16-2013iphone343_zps3f18294b.jpg.html?t=1366593272
I guess Q3 and Q4 have their influence on the sustain, right? I don't understand why there would be two transistors here. Isn't one sufficient to amplify?
I don't feel like replacing transistors just because I can. Want to keep it as original as I can!! So theory time. Who helps me understand the circuit?

[PRR]

> Isn't one sufficient to amplify?

Amplify how much? What do we want? MORE!! There's real limits how much true gain can be had with one transistor.

Here Q3 is a fairly linear gain of around 50. (Include Base and load impedances.) Q4 actually sits in cut-off, no-gain, at no signal. This helps mute hiss. Of course with gain of 50 in front, a little guitar will bring Q4 into action. Its Collector will slam big waves into the diodes Q5 Q6.

Bias of both these stages is rather loosely controlled. DCV checks of good and bad units may bring some insight.

[cortezthekiller]

From the sound demos I've heard the gated sound is normal with this Maestro fuzz. Unless yours is cutting out after the first second or two?

[VintageGear]

Yeah I guess you're right. I was comparing it to other demos but they had some booster along with it. Also if I use a high output guitar my sustain is way better. Ah well, was fun digging through the schematic! Now I'll pass on to my definitively broken maestro stage phaser. No phase audible. Hopefully I'll fix it on my own this time! Cheers

[bmsiddall]

Apologies for resurrecting this thread, but I built one last year with the same fast decay. Today I took another look at it. Snipped the Q4 47k base bias resistor and replaced with a 100k trimpot. Started at 100k and tweaked it until the hiss disappeared and I had a good level of sustain and nice gating on the attack. Killer circuit btw!

Cheers,
Brett

[pacealot]

I add my own apologies for necro-bumping this myself, but I felt compelled to confirm and expand on Brett's findings — I also put a pot at the base of Q4 (to be strictly precise, added a 25K linear pot to the pre-existing 47K resistor), and it makes it possible to fine-tune the exact amount of gating, including (surprisingly, to me) none at all, if one so wishes. This transforms this circuit for me into a hugely versatile fuzz that can still do what the FZ-1S is known for with all its Velcro attack, but which can now also get into seriously Muffoid territory with the sustain wide open. I am preferring the gating that happens on the larger-resistance side of the "no-gating zone" to that on the shallow end, but with the right combination of pot and resistor values you can have your que & can eat it, as it were. (Ahem. Sorry.)

Combined with a treble bleed-type cap across the sustain pot to improve the usefulness of the lower sustain settings (I think I settled on 0.0056µF), I now have a dizzying array of options on this one circuit. I highly recommend trying and tweaking to taste — there's way more in here than the stock original pedals (and their various YouTube demos) might have one think.

Oh, and also, I realised that I could use PNP transistors for the clipping diodes just as well as NPNs, and that helped me find a home for a couple of faulty 2N5139s that were otherwise headed for, er, shall we say, irretrievable obselescence (and they even look "vintage-accurate" to boot)....

[Mark Hammer]

I had one, or at least had the board, switch and pots of one, that a friend gave me, which I rehoused.  A terrific flexible fuzz, and one of the very first to allow blending of clean and distorted signal, via the balance pot.  The two switch settings allow for very different sounds.  If you see this schematic - ostensibly a "factory schematic" note that it is incorrect, and will not work, even though much of the design is revealed in it.  For instance, R14, R9, and R5 should be connected to V+, and NOT to the wiper of the Balance pot!    That wiper should go to R7 (the one pointing down, that is!), in order to mix the distorted signal in with the clean.  You will note the two halves of the Balance double pot are wired opposite such that turning the knob in one direction turns down one of the signals and turns up the other.  The collectors of the two "Q1" transistors in the upper half are connected to V+ and are NOT connected to


Here is the corrected version.

[kaycee]

Thanks, Mark for posting the corrected schematic. I built one from the erroneous schematic a few years ago and it was awfully gated and I was disappointed. One the most handsome old fuzz boxes I think.