Germanium Fuzz and Heat

[idy]

I didn't find a good thread dealing with this topic. What are your experiences with Ge fuzzes and temperature affecting performance? Care to characterize the changes? Are different models better or worse that way? Does the Bias control fix *all* or *most* of that?
Since the Buzzaround uses a Bias control in place of a volume (true or false?) does that help it "balance?"

[antonis]

https://www.diystompboxes.com/smfforum/index.php?topic=96102.0
https://www.researchgate.net/figure/C-V-D-V-for-germanium-and-for-silicon-as-a-function-of-the-normal-11-15-ized_fig1_230577950

[idy]

That paper would seem very helpful if I were interested in manufacturing semiconductors from Ge. Only discussion of temperature had to do with melt temperature and fabrication or am I missing something? maybe you are kidding me....

[idy]

And the forum thread hashes out the work bench measurement of temperature as if affects both leakage and gain. A hotter transistor is noisier and higher gain, no? I've heard of thermal runaway killing transistors...

I was fishing for observations of how that changes the sound or feel of a fuzz box. Does a (ff, tb, bb) sound noisier and gainier when hot? And is the bias control (usually I see on Q2) enough to balance the change?

[antonis]

maybe you are kidding me....

Not at all, but I might reconsider it..

So, instead of asking "nuisances", grasp a hair-dryer (for plastic enclosures) or a blowtorch (for metallic enclosures) and procced to your own deductions..

P.S.
If you hane the kindness, keep them for yourself..!!
(I don't think anybody would be interested for your particular conclusions concerning a very particular circuit under most very particular conditions ..)

[Electric Warrior]

And the forum thread hashes out the work bench measurement of temperature as if affects both leakage and gain. A hotter transistor is noisier and higher gain, no? I've heard of thermal runaway killing transistors...

I was fishing for observations of how that changes the sound or feel of a fuzz box. Does a (ff, tb, bb) sound noisier and gainier when hot? And is the bias control (usually I see on Q2) enough to balance the change?

No, a MK1.5/Fuzz Face will start gating when it gets hot. And not in a pleasant way. It sounds farty very quickly. When it's only slightly gating, a fresh battery will help with the tone. But the range in which it will gate and still sound good is very narrow.

The MKII improves on this by adding a buffer to the input - to keep the signal over the threshold of cutting out I guess. This makes the gating sound pretty good. My vintage unit only starts sounding unpleasant at well over 30°C.

Noise is not an issue at all, as it's gated out.
In my experience, temperature doesn't have much influence on hfe, but the leakage increases a lot. In a MK1.5, this brings down the voltage on Q1C, which in turn increases the voltage on Q2C. By tweaking Q1's collector resistor you can make up for this.

With modern FF clones it's probably not that much of an issue, as people tend to bias them very cold. MK1.5s had Q2 biased around 8V at room temperature. Fuzz Faces were biased a little colder. They vary quite a bit, but are usually well under 8V, but there is some overlap between the two.

[antonis]

Excuse me but I suffer from lack of terminilogy..

What is "cold" (or "warm ", or "hot") bias..??

[idy]

Two ideas there: that those 3 transistor models with a "buffer" might do better...
and that FF "tend" to bias their Q2 lower than tonebender mk1.5... also mitigating....? And a lot of those 3 transistor models have a diode that also *helps*?



Sorry; I know about nuisance threads where the asker slowly dances around the realization that his question reveals he doesn't know what any of the words he's using mean, or how to ask a meaningful question, or how to evaluate a source of misinformation... and/or asks a question that has been hashed out in a years-long thread from every angle...

I only have a couple of Ge fuzzes in the house now, a Buzzaround, a TB mk3, and a Buzz-alike. I am looking at my box of Russian Ge and wondering about what to try.

I tried the Buzzaround. I didn't have a hair dryer so I used a heat gun low setting, and after a few seconds...no fuzz, nada, I killed it!  After a few minutes it faded back, a little less splatty and gatey as time passed.  A few seconds with an ice cube and everything was OK again. I repeated with less heat.
My cheap multimeter is not doing temperature so I can't really quantify what is happening...

but maybe shoot for something that functions between say, 55 and 112F...? Here on the mountain or down in Palm Springs...
The TB, a pal took it the studio and loved it, then tried to show me at home his new sound... and couldn't find it. It is a three transistor model with diode. Maybe add a bias control to it and listen....

[antonis]

Didn't realize you're so pricly / excitable idy, hence I honestly apologize  and recall anything might seem dismissive..

[idy]

I am sorry Antonis I didn't mean to be prickly or seem offended, I appreciate your putting something in and recognize you as one of the knowledgeable people here. Excitable me...maybe.

The paper was kind of a deep dive (for me anyway) and seemed to be about fabrication of devices... "properties...relevant for device processing." Maybe there are answers in there...

And I wouldn't hold it against anybody to toss in a paper that was higher level work about fundamental materials science for a vague newbie question.  I thought you were kidding. No harm done. There is so much to learn, so many ways to go astray..

[idy]

And "Brother Silicon, Sister Germanium" is pretty poetic title. Could be a great name for a fuzz box. An an off-Broadway musical.

[Electric Warrior]

Excuse me but I suffer from lack of terminilogy..

What is "cold" (or "warm ", or "hot") bias..??

whichever way the temperature takes the voltages
In a Fuzz Face, cold would mean higher Q1C and lower Q2C voltage.