BSIAB II tweaking

[jmaund38]

Hey fellas, I just built the BSIAB II off of general guitar gagdets.  The build went quite well and im pretty pleased with the result.  However, I have one small issue with the sound.  When I flip my toggle switch to rhythym and play, it sounds good everywhere except for when I hit the 12th through 15th frets on my low E string.  It loses almost all of its distortion and gets really bassy.  In fact, it almost sounds as if its just humming the note.  Every other note sounds good, except for the ones mentioned.  I changed all of the JFETs to J201's which helped a little, but not much.  Its an awesome pedal except for that issue i have with those 4 notes.  Im just playing through a gibson les paul standard with the BSIAB II  into a marshall 1987x 50 watt tube amp, if that has anything to do with it.  Also, when i turn down the trim pot, that makes it sound better on those notes, but then everything else sounds like crap.  I know this sounds like a wierd problem, but any help would be greatly appreciated, thanks!

[jmaund38]

Ideas anyone?

[toneless]

Maybe the transistor needs a little biasing. 

[Ed G.]

J201's sound a bit bassy to me, I picked the 2n5457 in the spots that I did because they were a bit "tighter" sounding. I designed the circuit to sound pretty tight with the neck pickup of a strat, but that LP could be feeding it a bit more signal than that. Maybe back the neck pickup a bit, at least the bass side. I find pickups sound better a little further away from the string, even if you have to turn the amp up a bit.

[jmaund38]

Thanks Ed,  Ill have to move those pickups back a bit.  I almost always play with the switch flipped to treble, but sometimes i like to go to rhythym to get a nice creamy tone for a solo.  I've biased some of the transistors like toneless said.  It sounds like that did the trick for the most part.  But of course im at college now and am playing through an SG to a crate practice amp which is a different set up.  Cant wait to try it at home.  The BSIAB II is definately the best distortion pedal ive ever come across, and ive tried out alot!!!  But I have one more little question.  On my Q3 and Q5 transistors, I am getting 0 for the pinouts on the G pins. 

Q3) G:   0             Q5) G:   0
       S: .67                   S:  .81
       D:  4.44                D: 3.39
     
I see that you got .3 and .5 for your G pins on Q3 and Q5.  So I was just wondering if I was probing right...I put the negative tip to the ground and I touch the positive one to the pin whos voltage I want to read.  But both the G pins on Q3 and Q5 are connected to a ground (at least i think they are...im a newb what can i say?) , so a ground to a ground should be 0 which makes sense.  So am I probing correctly?  I was searching through the archives and came across someone elses pinouts of the transistors, they were similar to my readings and also got 0's where I did. So should I be getting .3 and .5 or is it fine to have 0's at those points?