mini driver 2 trannies

[dorothegreat]

im about to assemble the mini driver 2 from markm's gallery <http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/?g2_page=8>, im out of 2n5457 and it would of great help if you guys can help me by verifying that substituting it with j201 would be just fine. thanks 

[waltk]

Yes, it will work fine.  You can always socket Q1 and Q2 and try different JFETs if you like.

BTW, When I built this, I had some trouble making it work at all.  If I remember correctly, it turned out that I had a solder bridge somewhere.  After I fixed that, it worked great - so you can consider the layout verified.

[dorothegreat]

thank you very much!

i only have 1 2n5457 left, but i have 5 mpf102 and 15 j201. im looking for an od/dist of different character than that of my recent bsiab2 build.

[waltk]

I would try the J201 before the MPF102.  If your BSIAB2 has the JFETs socketed, you can also dramatically lower the gain of it by substituing 5457s and MPF102s.  I do this all the time to get lower gain out of a BSIAB2.
Good luck...

[dorothegreat]

do you mean that Q! would be j201 and Q woulb be mpf102 or try a pair of j201 first then a pair of mpf102? 

thank you very much

[waltk]

do you mean that Q! would be j201 and Q woulb be mpf102 or try a pair of j201 first then a pair of mpf102?

I meant that you should try either a pair of J201 or a pair of MPF102, and that the pair of J201s would probably sound better.

I usually use similar JFETs in both positions in a mu-amp (like in the mini driver), but they don't have to be the same.  I have read discussions about if/when transistors should be matched, and apparently this is not necessary in a mu-amp.  The sound you get out of it is almost entirely controlled by the JFET in the Q2 position, and the Q1 JFET is just playing a supporting role.  So I believe you can get different amounts of gain, and get different sounds by trying any of your JFETS in Q2, and it doesn't much matter what you put in for Q1.

You can find more information about the original circuit on the AMZ Muzique site, and more information about here by searching for mu amp.

Good luck - let us know how it works out.