A much early Christmas present for all you Tone Bender lovers... :)

[vanessa]

Thank David Main of D*A*M effects for looking under the hood of a few originals and letting us in on the good fun!

[nightingale]

Killer!

[gez]

http://www.muzique.com/schem/index.html

Scroll down for Maestro FZ

(Compare and contrast)

[alderbody]

gooooooooooooooooooood!

gooooooooooooooooooooooooooood!


thanX man! 

[Bernardduur]

What is B?? (power)

[ulysses]

thanks for that - any confirmation on the pro mkii?

i would say b is battery

cheers
ulysses

[oldrocker]

Would making it a negative ground a matter of reversing battery leads and all polarity caps?  I assume the transistors would have to be substituted also.  I suppose that kind of change would effect the sound of the circuit as well.  The PNP with positive ground is the magic behind this pedal.

[vanessa]

What is B?? (power)

I'm sorry it's 9V. I'll get to fixing that on the schematic as soon as my final exams are over. I barely could squeeze off this version but the suspense was killing me! 

[Bernardduur]

Thanks!

I wanted to see this for such a long time!

[R.G.]

Would making it a negative ground a matter of reversing battery leads and all polarity caps?  I assume the transistors would have to be substituted also.

Mother Nature says that you can reverse the power polarity of any circuit if you
(1) swap power + and -
(2) reverse every polarized part: capacitors, diodes, transistors, ICs, EVERYTHING that is polarized. Of course, with ICs there is often not an inverse polarity part to be had.

I suppose that kind of change would effect the sound of the circuit as well.  The PNP with positive ground is the magic behind this pedal.

In this case, there is a hidden dependency. Does anything strike you as odd about the biasing of Q1 and Q3? It should - there is only a resistor pulling the base in the "off" direction. There is no resistor providing bias in the forward direction.

Vacuum tubes and JFETs work this way. It's called "depletion mode" where the device is normally on and you just have to turn it off to the right amount to get things to function. Bipolar transistors don't work this way, unless they are leaky.

Germanium is about 1000 times as leaky as silicon. In this case, the germanium devices are leakage biased. The designer counted on the leakage of the devices being enough to provide bias to the devices. Q2 has some forward bias, but not much.

So how would you determine what the bias points of these transistors is? Easy - if you know the leakage. And you don't. Germanium always leaked a lot, and a highly variable amount. If you were using heavily preselected specific devices, you'd get semi-expected results. I've talked to Gary Hurst, and although we did not discuss this circuit, he's not the kind of guy to leave the bias point to chance, so the specific devices must have been tightly controlled.

What this means is that any build of this and the similar Maestro circuit will vary - a lot - depending on the exact germanium devices you put in. Just putting in OC75's won't necessarily do it either, because it was common back in the 60's to hand select or order hand selected devices. The OC75's you get today are likely the ones that were sorted OUT of the useful batch back in the 60's.

You'll have to hand select among pretested good germaniums to get the thing tuned up and sounding good. Of course, having been here, you know how.

[petemoore]

  There's no FF in that !!!
   

[vanessa]

David (D*A*M) told me that it's really a pain to bias this circuit and get it to sound right. I would guess a 10k trimpot on the collector of Q2 replacing that 2k2 would help. Bret found that transistors with some leakage contributed (for the better) to the tone of the Maestro Fuzztone, that might help some.
David also said that the fuzz knob acts more like it's tuning in fuzz like one would tune in a radio station than increasing in a linear fashion.

Oh! I forgot, he forwarded me some hfe's from a Gary Hurst reissue he had in his shop.

Q1 hfe = ?
Q2 hfe = 120
Q3 hfe = 92

I would guess based on others findings of the FZ-1 that Q1 is 50-70 hfe.

[R.G.]

David (D*A*M) told me that it's really a pain to bias this circuit and get it to sound right.

Yep. I'd have bet on that one.

Notice that the tone depend on leakage as much as on hfe. You can tune the bias point by tuning the value of those pull down resistors on Q1 and Q3 base. That has a side effect of changing the input impedance, too.

[vanessa]

David (D*A*M) told me that it's really a pain to bias this circuit and get it to sound right.

Yep. I'd have bet on that one.

I would also bet that it was the reason why the pedal was dropped from the Sola Sound line after only a year or so.

[petemoore]

  Funny how 'rare' equates sometimes to 'undesirable' or 'very sought after'.
  Neither or to me, just a circuit...like others sept. different.
  Undesirable' I would say so, if you're trying to produce 1 or mmany more than 1 unit with 'quick' results.
  Desirable if you want a circuit that does stuff other circuits which are easier to get 1 or more of functioning don't do....and you feel you have time to fuss to get Fuzz...will probably do gating tricks...because it's always next to, or 'over' one or more bias points..those kinds of 'edgey' circuits can be a fun play, but it takes a while to 'find' those bias points, so as to 'find' the intended effect, and then they might move again.
  And is a great sounding circuit [somebody thought so, long ago I surmize], it's quirkiness and dependance on a 'tweeker-ee', make it inherently 'rare'...not everybody's gonna wanna mess with it, of those, 'some' will make it work 'right', of those 'some' will actually find a place for it in the mix..

[DanielWong]

Curious...what is this pedal? Seriously...

[smnm]

http://www.stompboxes.co.uk/gpage1.html2.html

[DanielWong]

So it's just a Fuzz box?

[vanessa]

So it's just a Fuzz box?

Yes just a fuzz, but a very rare fuzz that has been a mystery for a long time now. It's one of the first commercial fuzz's, and one of the first to be heard on recording. There is some debate if it's the fuzz used (or the Maestro FZ-1) on the Rolling Stones "Satisfaction". For the fuzz geek having a copy of this schematic is like finding King Tut's tomb.

[DanielWong]

Is it better than other pedals or just rare?