BSIAB2 build report

[oldrocker]

Well after procrastinating building this pedal I finally bread boarded it.  I tried three different sets of trannies  (j201, 5952 and MPF102'S) in the first positions.  I actually liked the j201's best but there was too much noise when not playing.  The MPF'S and 5952's were close but the 5952's sounded a little better to my ears.  I'm still experimenting with some other trannies.  What tranny combinations worked best in your bsiab's.  I usually go for od over heavy distortion.  With this pedal I wanted it heavy while not incorporating the noise along with the higher gain.  I will keep at it with any suggestions.

[waltk]

To go way light on the BSIAB disdtortion, I've used MPF102s for Q1, Q2, and Q5, and put 5457s in Q3 and Q4.  I guess it doesn't matter so much what you put in for Q1 and Q3 because of their role in the mu-amp stages.  When I use this combination, I get almost no breakup when the drive pot is turned way down, and still a fair amount of distrotion when it's turned all the way up.  It can make a big diference where you put the high vs low-gain JFETs, so try swapping them around a bit... and don't forget to re-bias Q5 when you change it.

Can't say that I ever had a noise problem with the stock JFETs.  Under what circumstances are you getting a lot of noise?

I have a bunch of J201s, 5457s, and MPF102s, so I can measure Vp values and pick the ones I want.  Let me know if you want my Vp values also.

[Eric H]

j201's are not inherently noisier than the other ones you mention, i suspect they are biased wrong, or set-up for too much gain --do you have any other j201s to try?
Over the years I've come to the conclusion that recommending a JFET type, or brand in these types of circuits is useless unless the specs of that exact JFET are included as well. As you know, the specs on any JFET (unless pre-sorted) vary all over the map, so it's unlikely that
the holy grail combo for me, will work for you. YMMV, of course.
What I'm suggesting, of course, is what your doing now : find what works for you, in this particular application  

-Eric

[oldrocker]

Ok thanks.  I didn't realize Q1 may have a limited effect on the sound.  I do have quite a few j201's to try so I'll try others and see what I come up with.

[Eric H]

If I had seen your post, Walt, I wouldn't have sent mine  

-eric