Bsiab tweaks

[rockford]

I'm doing some tone tweaks to bsiab2, and had a few questions. Is C8 the actual cap for the tone control ? I put in a 1uf in place of .1 uf, and wondered if
going higher would yield a beefier tone, say 2.0 uf. Any ideas ?

[snoof]

C8 is just one part of the tone crkt.  if you want more low end, try .1 for C2.  Also C4 and C12 could be upped to .047 as well.

[rockford]

I'll try it. Right now, I have 1.0uf in C12, and wonder if it might be too much. What do you have in C14 ?

[StickMan]

I always wondered what would happen if you modified or removed that bleed cap on the pot between the two stages.

[rockford]

If you mean the 150pf, it has less high end at low drive, as driveis increased, more high is heard. This is AFTER the bleed cap is removed.

[StickMan]

So you've tried it then?

[rockford]

That's right, its smoother at low drive settings.

[StickMan]

Well that makes sense, the bleed cap comes into play when the resistance through the pot is highest.  I wasn't sure how it would actually sound in real life, though.

My big complaint about the BSIAB2 is that I'm almost always playing it with the drive turned way down, and it sounds a little choked off at that level.  It would be cool to figure out a way to reduce the gain of the first stage, maybe with a trimpot on the emitter - ground connection of the bottom transistor in the first stage - a la the "fuzz" control on the FF.  The you could leave that drive control a little more open and get better rounded sound.

[m-theory]

It would be cool to figure out a way to reduce the gain of the first stage,

Replace the J201 JFETS with 2N5457.  Works magic to drop gain and make the pedal more articulate. 

[snoof]

I'll try it. Right now, I have 1.0uf in C12, and wonder if it might be too much. What do you have in C14 ?

1uf seems a bit high to me.  I would think that .047 or .1 would be the highest that you would need, but YMMV.  I leave  C14 out of the crkt altogether.  I usually stick a .1 in C2 and that does the trick for me.  My thought is the you need to raise both C4 and C12 to get more low end through.  If you raise C4 and not C12, you might be choking off that additional low that you just let through??

mpf102 is another low gain tranny to try.  they seem to be a bit brighter as well.  You could also raise R3 and/or R10.  I have a pot on R10 in mine.

[rockford]

OOOPS... I meant that I put   0.1 in C12, NOT 1.0.

[StickMan]

I thought the MPF102's were higher gain than J201.

[snoof]

I could be wrong, but I've always been told that they were lower gain than 201.