Switching Transistors in the BSIAB II

[robotboy]

I built the BSIAB II a little while ago and contrary to other's experiences mine was TOO mid-heavy or maybe upper-bass heavy. Anyway, on my rig (a rivera knucklehead and les paul jr. w/ P90's) I had to turn the bass way down to keep it from sounding too thick (it's a pretty bass and mid-heavy setup to begin with). I just spent about an hour screwing around with a variey of transistor combos ranging from all J201 (really compressed) to all 2N5457 (really really full sounding). I even accidentally swapped in a BS170, which made it splatter out and sound like complete sh*t  :wink: . I finally found my magic combo by subbing a 2N5457 with a J201, leaving me a total of 2 2N5457 and 3 J201, which took away almost all of the murkiness and left me with a REALLY sweet sounding distoriton. It may be due to variations in my FETs gains, but I haven't measured them because I'm too lazy. Plus it's more fun just popping them in and out until the "golden sound" emerges. It's pretty awesome how many tone and compression variations you can get just by messing around with the bias screw and swapping trannies. Sorry there's no real point to this post. I'm just having too much fun enjoying a build instead of rushing onto the next one. I'm going to build the blackfire now that I'm satisified with this and let a friend choose between the two of them. He's a hard-working rocker, and it's soooo cool to be able to hook him up with something he'll be using for a long time and probably taking all over the world on tour.

[mojotron]

Which 2N5457 did you sub with a J201 in the BSIAB2 schematic?

[robotboy]

Which 2N5457 did you sub with a J201 in the BSIAB2 schematic?

Q5, but I didn't use any engineering to make the decision. It was simply a matter of swapping until I found the exact sound I was looking for.

[mojotron]

Which 2N5457 did you sub with a J201 in the BSIAB2 schematic?

Q5, but I didn't use any engineering to make the decision. It was simply a matter of swapping until I found the exact sound I was looking for.

Ahh yes.. I'll give that a shot.. thanks

One thing I found is that the J201s in q1 and q2 boosted the low end a little too much.. In short, this circuit gives a lot to tweak. Another cool mod is to make R6 a 1M pot. At 0 ohms, the sound is really fat, and at 1M ohm, the tone is really edgy

[Rutherberg]

One thing I found is that the J201s in q1 and q2 boosted the low end a little too much.. In short, this circuit gives a lot to tweak. Another cool mod is to make R6 a 1M pot. At 0 ohms, the sound is really fat, and at 1M ohm, the tone is really edgy.

If I change Q1 and Q2 by J201, I would have more the low end ? Because I find that my BSIAB cuts too the low end.
Thanks

Rutherberg

[Rutherberg]

Hi,

I initially replaced Q1 and Q2 by of J201, and I had indeed more the low ends. I also changed Q5 by J201 and the distortion of low is less cracking, more pleasant with the ear and still more low ends