Another Fuzz Face clone voltage thread

[MojoHand]

Hey all,

I have been searching for the info I need for a couple hours and am not finding it.  Please forgive if my patience has run thin and started a thread that has been covered elsewhere.

I have just completed my first DIY project, am a total noob, and would really appreciate some insight.  My FF clone was built using the General Guitar Gadgets FF5 Germanium http://www.generalguitargadgets.com/projects/73-fuzz-tones/101-fuzz-faces schematic and PNP germanium transistors matched by Small Bear.  The only mod I made was to change the value of the 1k resistor at R% to10k to get Q2 collector voltage to 4.53.

The pedal works and actually sounds pretty darn good except that there is much less sustain than I expected, and it actually seems to gate at the end of a note.  I figure this is a bias issue but I'm not sure what to try to remedy.  My voltage readings are (with the voltages from the FF5 instructions in parentheses):

Q1
c:  0.58  (1.4)
b:  0.11  (0.6)
e:  0.0  (0.0)

Q2
c:  4.53  (4.5)
b:  0.58  (1.4)
e:  0.5  (0.

Thanks for all your help.  I've been pouring over this forum for weeks before actually beginning and it's helped immensely. 

Kindest regards, and thanks again.
--Greg

[Earthscum]

My guess is you have the transistors backwards... meaning not that they are upside down, but rather your high gain tranny is where the low gain should be, and vice versa. I got the same kind of effect, but not as pronounced, by using same gain transistors. If you read through R.G.'s Technology of the Fuzz Face he talks about matching the transistors (I'm willing to bet you've waded through that one). Also http://www.diyguitarist.com/DIYStompboxes/FF-Notes.htm was helpful when I was trying to tune FF's to my liking.

[MojoHand]

Thanks for the reply, Earthscum.

I switched the transistors and got the following voltages:

Q1
c:  0.5
b:  0.10
e:  0.0

Q2
c:  5.26
b:  0.5
e:  0.4

It seemed to have a bit more sustain, but not what I was expecting still I guess.  When I adjusted the trimpot so that Q2's collector was 4.53 it seemed to weaken considerably, also.  Would you expect that the collector voltage would increase or decrease when I changed them around?

Maybe my expectation needs adjustment, but I'm looking for that creamy-Hendrix-y sustain forever sound.  Perhaps that's a product of amp volume more than the fuzz.  I've read the RG's paper, and I'll check out that other article you suggest.  

Thanks for the help.  I appreciate it deeply.

--Greg

[petemoore]

  You can make the 8k2 adjustable between 4k7 and 14k7 using a 4k7 stop resistor/ 10k pot as Q2Cresistor.
  This is a common point of bias adjustment to accomodate various transistors, especially useful when working with Ge transistors, they can vary a lot.
  Maybe they're ok voltages [they don't look far off] for sure can't say without the supply voltage.

[MojoHand]

Ah, forgot to post the supply voltage.  I even read that...

Battery reads 8.69v.

I do have the 10k trimpot in place of the 8k2, actually.  I was surprised by the difference in the Q1b and Q1c being so far from the manual's values.  Maybe that's not a big deal?

Thanks!
--Greg

[Earthscum]

I'll have to double check my newest one when I get it finished... I think I was getting the best sounds when I was biasing the thing so my Q1 base at around .5V  and my Q2 collector at (with a power supply... drops about .2V with the battery).

I'm also doing something probably bad and using NTE158's. I think they sound great, and the gains have (so far) been pretty consistent, as well as leakage. They actually have around 140 gain after leakage, so I have to lower the collector resistors a bit to get it to bias right and cut out some high end. My buddies all love them... they all own at least one Si FF (red must've been the popular time to buy FF's). My friend I named the pedal after actually has the JH FF that he's gonna bring by for me to mod, but it doesn't hold a candle to the original Ge circuit.

[petemoore]

  You know the bias knob is sufficient range when it causes misbias at both ends of the pot R range.