What to make with 30-50 hFE Germaniums

Feral Feline said:
Go the other way with a Double-AA, eh?

Some of the ol' fuzzircuities used two or even one AA — 3v or 1v5 respectively.


"Maestro Fuzz Tone started as a 3 volt (2 AA batteries) fuzz, then went to 1.5 volt, and then 9 volts (versions FZ-1, FZ-1A, and FZ-1B respectively)."

HEATHKIT TA-28 FUZZ 1v5
Fi-Sonic Fuzz Blender [Maestro FZ-1 variant from down under] 3v


A lot more obscurities are out there, hidden in old electronics magazines, musician magazines etc...


Who needs a knob for "battery-sag" or "voltage starve" when you can just run it right at 1v5 or 3v?
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Good point, I think. :) My only caveat is that they might be even harder to tune with reduced voltages.

I've spent most of the last three days or so building Zonk variants and I realise again why the world of PNP Germs is so utterly bizarre (at least to me). I found a nice Zonk II schematic at amplified parts, modded my hitherto functional breadboard version, and got fantastic results from it. Around two hours later, it stopped functioning altogether. Dead silence when engaged...

I built a cleaner version with the same components, thinking maybe the breadboard itself was funky. Same result, silence.

Voltages look plausible, transistors read ok with Peak tester. Could this behaviour somehow be temperature-related, that the Germs just close off at a given temperature? So much to learn, so little time.
 
mybud said:
Good point, I think. :) My only caveat is that they might be even harder to tune with reduced voltages.

I've spent most of the last three days or so building Zonk variants and I realise again why the world of PNP Germs is so utterly bizarre (at least to me). I found a nice Zonk II schematic at amplified parts, modded my hitherto functional breadboard version, and got fantastic results from it. Around two hours later, it stopped functioning altogether. Dead silence when engaged...

I built a cleaner version with the same components, thinking maybe the breadboard itself was funky. Same result, silence.

Voltages look plausible, transistors read ok with Peak tester. Could this behaviour somehow be temperature-related, that the Germs just close off at a given temperature? So much to learn, so little time.
Click to expand...
Needless to say, it was a wiring error on my part.

Step 1: Learn not to make cloth-brained mistakes.
Step 2: Avoid publicising one's errors to the wider world.
Step 3: Repeat step 1 ad nauseam.
 
rossbalch said:
Could be fun, any sweet example circuits?

I probably have like 100 devices in this range, so I could make quite a few things ha ha. Would really love to do a microphone preamp, and line amp too.
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A cascode is a great way to increase gain, but it has lousy PSRR and a high output impedance. Often you’ll see a cascode followed by a cathode follower. This means you get increased gain and then a driver to stop the next stage/pedal from seeing a high impedance. Furthermore, you’ll want a stopper resistor on the input as it may pickup RF due to the same increased bandwidth.
What that means is your los hfe can be used to get more gain.

I don’t have a specific circuit but a fuzz or distortion can be built using it. If there’s too much gain you could use some NFB or even abuse that for nee tones.
 
NickKUK said:
A cascode is a great way to increase gain, but it has lousy PSRR and a high output impedance. Often you’ll see a cascode followed by a cathode follower. This means you get increased gain and then a driver to stop the next stage/pedal from seeing a high impedance. Futhermor, you’ll want a stopper resistor on the input as it may pickup R lF due tothe same increased bandwidth.
What that means is your los hfe can be used to get more gain.

I don’t have a specific circuit but a fuzz or distortion can be built using it. If there’s too much gain you could use some NFB or even abuse that for nee tones.
Click to expand...

Yeah there's no reason the design needs to be all Germanium, would be fine to use a JFET input buffer for instance, and a Si BJT follower to buffer the output.
 
IMG_1864.jpeg

I breadboarded this Zonk II (following some experimentation with values, eventually settling on the Amplified Parts version: details here.)

I like it so much that I built a Vero version, as above.

This seems much more forgiving than the Zonkbox and gives a nice creamy sustain and lots of volume on tap.

Used the following configuration:

Q1 AC128 (hFE 80, leakage 0.243mA)
Q2 OC75 (hFE 97, leakage 0.294mA)

Also added a charge pump because this seems to help the circuit stabilise (more than straightforwardly reversing the voltage and electrolytics) and for compatibility with a centre negative setup as most pedals need. I prefer C1k for B1k for the fuzz control, obviously a matter of taste.

Is this entirely relevant to OP's question about low gain Germaniums?

No, but the circuit's fun anyway :cool:

Thanks for reading as ever and best of luck with your projects.
 
mybud said:
View attachment 100307

I breadboarded this Zonk II (following some experimentation with values, eventually settling on the Amplified Parts version: details here.)

I like it so much that I built a Vero version, as above.

This seems much more forgiving than the Zonkbox and gives a nice creamy sustain and lots of volume on tap.

Used the following configuration:

Q1 AC128 (hFE 80, leakage 0.243mA)
Q2 OC75 (hFE 97, leakage 0.294mA)

Also added a charge pump because this seems to help the circuit stabilise (more than straightforwardly reversing the voltage and electrolytics) and for compatibility with a centre negative setup as most pedals need. I prefer C1k for B1k for the fuzz control, obviously a matter of taste.

Is this entirely relevant to OP's question about low gain Germaniums?

No, but the circuit's fun anyway :cool:

Thanks for reading as ever and best of luck with your projects.
Click to expand...
Thanks for posting. I have this circuit in my table. You notes will help me select some good transistors. 😁
 
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