BC108 in a Fuzz Face ...

[Melanhead]

Just got a batch of 'em from Small Bear and noticed that some say they sound great in a fuzz face ....

My confusion lies in the hfe part ... I've read that suggested hfe for Q1 is around 70 and Q2 being around 130.

well I haven't found a BC108 lower than 200! ... is it more ratio ( Q1/Q2) based or am I going to get into some Extreme fuzz

[brian wenz]

Hello Hello--
   The lower hfe gives you a sound closer to germanium Fuzz Faces  [ Q1-70, Q2-120-or-so], but you can get great silicon fuzz  using high gain trannys as well [it'll just be "different"].  Both are great for different things!
Put sockets in a "test fuzz" and try different combos of trannys.
Brian.

[Melanhead]

thanks Brian ... was planning to socket 'en and try a bunch... I'm sure I'll discover some great and not so great tones

[brian wenz]

Hello Hello--
    Try a real high gain [500hfe  + ] for Q2 and  a lower gain  [100hfe] for Q1  and see what ya think!
Brian.

[Melanhead]

great ... I'll give it a shot ... and post the build when done ..

Thanks again ...

[petemoore]

I think good' cleanup at guitar is a little different [more 'pristine'] with gains of 90-150hfe at Q2, Q1 is 'Pickier' about the low hfe for 'good FF.
 I keep typing 'apostrophe good' 'cause higher gain Q2 makes for a more saturated sounding Fuzz with less 'input voltage'.
 BCxxx's seem to add a certain 'BC' character to the distortion.
 My FF's work with less oversaturation using the volume pregain knob or guitar volume...at some point the saturation turns muddy, takes the 'slice' out of the attack sound, different harmonic structure with sustain.

[brian wenz]

Hello Hello--
    Yeah, that's true.  Then there's the kind of sound you get by putting a high gain tranny in Q1 and a LOW gainer in Q2!
Brian.

[mojotron]

What I do, which is close to what was mentioned above, is to swap out several BC108 transistors putting lower gain one in Q1. If you're going for a Ge FF sound you might do better with some other transistors. However, if you're going for that raging Si FF sound the BC108 transistors are perfect - but there is no clear standard with high gain transistors other than putting the lower gain of the pair in Q1.

Of course, the thing everyone likes about the FF is that each one is a bit unique sounding..

[nag hammadi]

i have just finished a fuzzy build, and was trying to use two bc108's.  i loved the insane fuzz, but there was no way to tame the insane squeeling between (and sometimes during) notes.  i changed one out to an ac127 and that fixed the problem up nicely... BUT>>>

i REALLY liked the fuzz tone better with the 2 bc108's. 

anyone have a suggestion on either A) a way to tame the squeel from dual bc108's, or B) i good choice for a replacement of ac127 (maybe a little higher gain)?

thanks,
emanual

[radio]

I build the colorsound oneknob fuzz with bc107b as q1,q2 for bc108b

in my opinion this is amazing crunch.

Greetings JME

[manson]

Yeah you could perhaps use a bc108a for Q1, and bc108b for Q2 to give you a lower/higher hfe setup. BC107 and 108 are almost identical.

[Melanhead]

i have just finished a fuzzy build, and was trying to use two bc108's.  i loved the insane fuzz, but there was no way to tame the insane squeeling between (and sometimes during) notes.  i changed one out to an ac127 and that fixed the problem up nicely... BUT>>>

i REALLY liked the fuzz tone better with the 2 bc108's. 

anyone have a suggestion on either A) a way to tame the squeel from dual bc108's, or B) i good choice for a replacement of ac127 (maybe a little higher gain)?

thanks,
emanual

Hmmmm ... I use BC108's all the time now with a Fuzz Face type circuit and have no probs with squeal ... Not sure what to recommend other than maybe it's a lead dress issue.

[nag hammadi]

all of my joints and points seem good.  is there something specific in terms of "lead dress" that i need to look at?

thanks guys.

[Gus]

this circuit is designed to tame the first transistors gain

http://www.diystompboxes.com/pedals/gusFuzzFace.gif

You can drop in si transistors without major adjustment.  Adjust the bias pot by ear, plus it gets different sounds at the ends of the bias pot travel

[Sam]

I for one certainly found the use of BC108s to be a great improvement in my Si FFs. They sure gives a nice hi-gain fuzz tone with a hint of "vintage FF character".

[ErikMiller]

all of my joints and points seem good.  is there something specific in terms of "lead dress" that i need to look at?

thanks guys.

My Crucible Fuzz uses a pair of BC109C's, with no hFE lower than about 350, and it does not oscillate.

I had to tweak my layout to get it not to oscillate; you want the connections between the Q2 collector resistor, the resistor on the other end of that resistor, and the output cap to be as short and direct as possible. Put the connection to the cap between the connections to the other two, so that it's just like it is on the schematic.