Can you match a Ge Fuzz Face tone with Si transistors?

[Kevin Mitchell]

I don't know about you but my express goal is to avoid the temperature sensitivity of Ge transistors by using Si, but emulating their tonal characteristics.

Understandable. I tend to enjoy the unstable nature of Ge 

[Grunfeld]

I don't know about you but my express goal is to avoid the temperature sensitivity of Ge transistors by using Si, but emulating their tonal characteristics.

Understandable. I tend to enjoy the unstable nature of Ge 

Some people just want to watch the world burn lol

[antonis]

Seeing as tantalums aren't polarized.

Tantalums are innately polar devices..

[Grunfeld]

Seeing as tantalums aren't polarized.

Tantalums are innately polar devices..

Oh I guess I was misinformed then.

[mozz]

They do not like to be hooked up backwards either. The polarity markings are usually different than you would see on a electrolytic.

[duck_arse]

Seeing as tantalums aren't polarized.

Tantalums are innately polar devices..

Oh I guess I was misinformed then.

don't get the tantalums confused with the monolithic ceramics, or mlcc's. tantalums will short and burn if connected reverse to thier marked polarity, mlcc's don't care either way.

[cab42]

Also, use sockets for the transistors.  You may want to audition different ones to see what sounds best ti you.

I built the Schizoid Fuzz a while ago, and transistor swapping was definitely the fun part! Other than at a point I lost track of which combinations of transistor models and gains I had already tried. I ended up using a mpsa06 for Q1 and a BFT40 for Q2 with gains around PJP's recommendations.

When I took it off the breadboard I found out that I had used a 6.8k instead of the 8.2k at Q2. Socketed the resistor on the board, but couldn't decide, so I added a 10k pot instead. Lots of sounds available! My favourite setting is around 7.5k.

[LightSoundGeometry]

my vote is yes! SI bjts work very well sometimes.

[LightSoundGeometry]

Seeing as tantalums aren't polarized.

Tantalums are innately polar devices..

Oh I guess I was misinformed then.

according to Mr Carlson, all caps have polarity !!

[matopotato]

I would put trimpots for biasing both transistors. It gives you a chance of fine tuning bias, and it a nice learning experience as well.
I built a FF out of a 70's TV set and also added a trimpot for the volume. All three helps dialing it in. I had Ge's though.

[Big Monk]

I don't know about you but my express goal is to avoid the temperature sensitivity of Ge transistors by using Si, but emulating their tonal characteristics.

I agree with this. Leakage and it's effects on temperature driven voltage fluctuations is not a desirable characteristic unless you are trying to fit the transistors to the classic circuit values.

There is value in improving on some of the vulnerabilities of the original circuits.

If I want a circuit to gate or spit, I'll design it that way or include a bias control that allows that function to be variable.

[pinkjimiphoton]

It really depends on what you mean by "match".
Can you make a 100% accurate clone of a particular Ge fuzz with magic Si transistors?  Probably not.
Can you make something that reasonably captures many of the qualities you like about a Ge fuzz using Si transistors? Probably yes.
Pinkjimiphoton made a couple projects that aimed for this:  the Stupid Face and the Photon Face, combined into the Schizoid Face.  Search for those, or wait until I dig up a link.....

Obviously it's going to come down to something pretty subjective. I don't think I can explain it any other way than I already did. The Ge fuzz has a certain smoothness that I'd like to achieve with the Si one, but haven't been able to.

the only way to get the smoothness of a ge fuzzface outta si is to add resistors between e and ground.
you bias from the c resistance.  bias sets the range of the operation of the q.

but that has no effect on the GAIN of the q. this is the important part. you can bias damn near any q from the collector and get it to pass signal and fuzz, but too high, and the ff doesn't sound right, way too harsh and noisy. not enough, and its like a dirty broken compressor.

but... by adding resistance to the e/earth node, you can adjust the GAIN overall of the q, and get it into the ballpark for the gain that will make the circuit sound best.

you could use 1k trimmers if ya want, to find where it sounds best then measure it and replace with closest standard value fixed resistors, or try the suggested values for the schizoid face. adding them resistors makes a huge diff.

and you can always be creative with a ge diode to mimic it a little more, try it in both orientations, between the different nodes of the q. some will work, some wont but it may help you learn and figure out how to get the tone you seek.

that said, it will never be exactly the same as ge.

[pinkjimiphoton]

Also try 100pf caps across the C-B junction of both transistors.

thats pretty big. start around 22pf and work your way up. most of the time, 47-56p is enough

[pinkjimiphoton]

Seeing as tantalums aren't polarized.

Tantalums are innately polar devices..

Oh I guess I was misinformed then.

according to Mr Carlson, all caps have polarity !!

they do, the part marked with the black stripe is the outer wrap of the cap, and should go towards ground. helps act as a faraday cage and keeps hum down.