2 Fuzz Faces tonepad germanium totally different sounds - why?

[billkahler]

I recently built a second tonepad Fuzz Face with germanium transistors from Small Bear. I followed Steve's instructions for resistor values and all the other values are correct. My first one had a very round warm tone (wooly?) but this one sounds a bit more like a distortion box (edgier) and to my ears not nearly as cool as the first with its creamy warm sort of tone. In the second one I did use some different components even though the values were correct. Some how I ordered carbon comp resistors from Mouser instead of carbon film so I put those in. Also one of my caps is a "greenie" and Steve says the orange ones sound better. I also used a reverse log taper pot for the fuzz control as suggested on some of the boards. My question is would the cap and resistors make such a huge difference or is that mojo and is it possible that the germaniums sound different from pair to pair? Is it possible to change a couple resistor values to overdrive the transistors a bit more? Another weird thing is the tone seems to change a bit when it's warmed up! I know . . . that's really weird. Thanks in advance for the help.

[petemoore]

and is it possible that the germaniums sound different from pair to pair?
  Oh yes, see GEO Technology of the Fuzz Face for more info
  Another weird thing is the tone seems to change a bit when it's warmed up! I know . . . that's really weird
  Not too wierd, bias drift.
  Try heating one up with your finger and watch the bias point @Q2c move.

[Nashtir]

I saw a '69 Fuzz from Fulltone..the sound can extremely change according to the gain of the transistors.. he uses trannies with values of: q1:88 q2:105 meaning that the sound of his pedal comes and varies so much changing transistors..You could use selected trannies from banzai!

[GibsonGM]

I find that with any Ge fuzz, I have to use bias pots on the Q's to dial in the correct 'sound', and they will drift after being used for a little while and require tweaking.   I brought a pot right out to the top of my enclosure for the bias on q1, and just give it a nudge after it's warmed up.  Makes a world of difference!  If I hadn't found that out, I'd have thrown the ckt away...

[brett]

Hi

I recently built a second tonepad Fuzz Face with germanium transistors from Small Bear.

this one sounds a bit more like a distortion box (edgier) and to my ears not nearly as cool as the first with its creamy warm sort of tone

My experience exactly.  My pair from Small Bear had high hFE and sounded harsh with the recommended resistors.  Reducing the collector resistor on Q1 helped (mine is hFE = 140, R is now 22k).  Sombody (maybe Gus ?) also suggests increasing the feedback (resistor from 100k to 47k).  Both these things might throw the bias of Q2 out, meaning that you'll also need to adjust the resistance on the collector so that its voltage is 3.5 to 5.5V.  (There are many old threads on biasing the fuzzface).
cheers.

[RaceDriver205]

Try heating one up with your finger and watch the bias point @Q2c move.

Serious! Has anyone tried rapping a heater-wire around a Ge transistor for tone alteration?

And can anyone here tell me if there is actually anything special about Ge Fuzz? Especially considering the price and hastle of the parts. Is it just a nostagia thing?
Enlighten us, RD205

[KerryF]

The HFE values on the gemanium transistors in each are probably different.

[Seljer]

Serious! Has anyone tried rapping a heater-wire around a Ge transistor for tone alteration?

the heater thing would just shift the gain to somewhere else and probably misbias it badly, and add a lot of power consumption to a circuit that uses barely anything on it own. Use an external pot for the bias resistor and you can mess around with misbiased sounds whenever you feel like it.

[Primus]

I would avoid adding any additional heat to a Ge transistor. They are very very sensitive to heat and you could damage it very easily. If you want to get a more consistent bias, you can use a pair of 1n34a Ge diodes reverse biased from the base to the emitter of Q1 and Q2. This will prevent thermal runaway. Please see the outstanding article on this at Plate to Plate: http://www.geocities.com/sunsetstrip/studio/2987/britface.html

[billkahler]

Thanks for all the help - I'll continue working on this and see what I can do.

[petemoore]

I'll continue working on this and see what I can do.
  Barring luck, that's what it takes...

[Quackzed]

the input cap had a big effect on the wooly vs. edgy type sound i bet you've got a smaller input cap on the edgy one right? betcha!

[Dai H.]

I have a bunch of mostly Japanese Ge transistors plus some American ones bought from Antique elec.supply ages ago, and plugging them into a FF cct. w/variable 33k(50k pot copied from the RM Classic Fuzz)I did find that sort of thing also (some "round" some sharp and edgy-sounding), some saturated, some having more definition (some having no output at all...lol). IIRC Analogman has some sound samples of real NKT275s and something quite close, and they are a hair different on the sound samples (bit more edge on the near-NKT275s, and it seemed that way with some of mine also (2versions of 2SB167?). I don't know which specs were responsible for the differences (gain, HF response, etc.)but the sound character did seem different (also the same with various Si transistors). 

[brett]

Hi

tell me if there is actually anything special about Ge Fuzz?

Good question.
Although I'm a fan of the axis fuzz at fuzzcentral, there is at least one reason why germanium gives a superior sound.  Germanium transistors have a base-emitter voltage difference of about 0.3V, while it is 0.7V for silicon transistors.  A germanium Q1 clips smaller signals and clips them more more asymetrically than a silicon Q1.  It seems to make a reasonable improvement in tone.
Other differences relate to junction capacitances (as reflected in the low Ft of many germanium devices, including the more "creamy" ones maybe), but it is difficult to tell how much difference these things make.
cheers   

[RaceDriver205]

Yeah Ok, i listened to a sample or two of Ge fuzzes, and they do seem to have a distinctive tone to them. May as well just make one whether I decide I like the tone or not. At least I can say my multifx box has "old school Ge Fuzz" too.
I recon ill make the tonepad TBMkII, and buy the Ge's from smallbear.

[Somicide]

Try heating one up with your finger and watch the bias point @Q2c move.

Serious! Has anyone tried rapping a heater-wire around a Ge transistor for tone alteration?

And can anyone here tell me if there is actually anything special about Ge Fuzz? Especially considering the price and hastle of the parts. Is it just a nostagia thing?
Enlighten us, RD205

a while back, there was a huge discussion on piggybacking Si trannies to get a more germanium tone, IIRC.  Would make making a FF much easier, since you could control the gain a little easier with the circuit.

http://www.diystompboxes.com/smfforum/index.php?topic=17513.0  there it is, or portions of it.