Bias silicon fuzz face

[rangermaster]

Hi

I'm planning to make a silicon BC108 fuzz face this weekend.

But what about the bias voltages in a silicon npn pedal ?

Should it be the same as with a germanium: Q1-C 0.50v and Q2-C 4.5v ?

Thanks

[mozz]

Q1 will be higher, over 1v.

[Steben]

Hi

I'm planning to make a silicon BC108 fuzz face this weekend.

But what about the bias voltages in a silicon npn pedal ?

Should it be the same as with a germanium: Q1-C 0.50v and Q2-C 4.5v ?

Thanks

Like mozz said. Q1-C depends on the gain of the tranny's. Trim trimmy trim.
BC108 around 200 - 250 sounds great, they will render JHF-1 territory, the turquoise devine.

[rangermaster]

Tnx for the replies.

Ok so q2 4.5v and q1 around 1.5v should be good?

The transistors are coming in this weekend so i don't know what the Hfe is yet.

Datasheet: https://www.bitsandparts.nl/documentation/350/BC108.pdf

[Gus]

some links that might help
Don't get stuck on 4.5VDC that is a web thing try different collector voltages

https://www.diystompboxes.com/smfforum/index.php?topic=114153.msg1059002#msg1059002

https://www.diystompboxes.com/smfforum/index.php?topic=112880.msg1044061#msg1044061

https://www.diystompboxes.com/smfforum/index.php?topic=112341.msg1036524#msg1036524

[mozz]

 I usually trim Q1c and q2c will follow, much easier. I'm thinking more about 1.2-1.3v.
Trim the 33k and when you get to 4.5v on q2c just measure q1c. Then after that adjust to where you like the sound, take notes.

[percyhornickel]

BC108  BC109

Q1c: 1.3V
Q2c: 5.7V

The sweetpoint / This is what I use in my FF, just like analogman sunface.

Great sound.