transistor questions!

[Keysershades]

Hello, i was looking at the local electronics store the other day and found some 2n3903 and 2n3905 and remembered that the Roger Mayer Axis Fuzz uses 2n3904 and 2n3906.. Would the 03 and 05 be any good in a "axis fuzz" kind a thing ? Or is it just stupid ?

Shades

[scott_v]

Need to know the Hfe, i looked up the datasheets on these and i believe the Hfe of the 2N3903 & 2N3905 (which are similar to each other) are about half of a 2N3904, so its a low to medium gain transistor... not exactly sure what is actually recommended for transistor Hfe in that circuit, need to look it up... my guess is that you'll get less fuzz using those transistors and will need to tweak the bias abit more as opposed to using a 2N5088 or 2N3904... i believe the axis face is a close variant of the fuzz face i believe its preferable to use a low gain Q1 and a higher gain Q2, so it might be worthwhile trying to use the 2N3903/2N3905 for Q1 and the 2N3904 for Q2.

[jrod]

Yeah, like scott_v said, 3903/05 look to be lower hfe than 3904/06. But, who knows, they may work well. If they are cheap, I say buy a few and try them out. 

[GibsonGM]

Yeah, get a few...you don't always want maximum gain! 

[Keysershades]

Yeah i just became a fan of low gain transistors after i build my Sili Face with BC109C! They are nuts...
The 03 and 05 are half (or less) than the 04 and 05 (the original in the Axis Fuzz) and way easier to come by!

Thanks for the help, i think i'm gonna try it out

[zombiwoof]

Yeah i just became a fan of low gain transistors after i build my Sili Face with BC109C! They are nuts...
The 03 and 05 are half (or less) than the 04 and 05 (the original in the Axis Fuzz) and way easier to come by!

Thanks for the help, i think i'm gonna try it out

BC109B would also generally have lower gain than BC109C.  I recently got a large lot of BC337 and a sample of them measured between 275-350 hfe, a little lower than the range of BC109B's I've had, although it can vary a bit from one batch to another.

Al

[Keysershades]

But have you ever experienced some BC1xx to be more noisy than other ?

Simon

[Ronsonic]

But have you ever experienced some BC1xx to be more noisy than other ?

Simon

Yes.

Sometimes to an annoying, gotta audition the damn things before soldering in extent.

[zombiwoof]

But have you ever experienced some BC1xx to be more noisy than other ?

Simon

Generally, BC109 is listed as a "low noise" tranny, BC108 is not.  I don't know if there is an appreciable difference when used in a fuzz/wah pedal or not, but I try to use BC109 over BC108 because of that.

Al

[Keysershades]

But my Fuzz Face has this kind a loud hish and buzz, and it "disappears" when i hold my hand close to it (not touching it)...!?
Is that a ground problem ?
And how to get rid of it ?

Simon