Testing JFETs for the BSIAB II: anybody bother?

[Bucksears]

I had a great sound going in my BSIAB II, but (like a fool) pulled the JFETs when trying some others. I don't remember which ones I had in there and now I don't quite have 'that sound' anymore.
I love the sound of the BSIAB II stock config for higher gain, but also love the all-5457 approach for a little lower gain/slightly chimey sound.

Has anyone bothered ever putting in JFETs that were rated a particular gain/voltage?

Thanks,
- Buck

[ubersam]

I had an all-J201 once. I thought it sounded 'bigger' than the stock config with 2N5457s in the first stage. However, it was pretty noisy. But I think that was more because I used carbon film for the two 1M strings for the first and second stage.

[DoobieK]

I have a dual BSIAB. At first, I didn't match any of the FETs. I tried sets of J201 and 2n5457. Both circuits sounded different. One was more full than the other. Then I tried all J201 and matched each pair. Both circuits sound much more similar and both sound full. If I had matched all 4 maybe they would sound identical. Since I use one for moderate overdrive and one for major distortion they don't need to sound identical. They probably sound similar, like two different amps of the same make and model.

[jrc4558]

I never measured j-fets i nthis application, but must I say that I had exactly the same "I don't quite have 'that sound' anymore." experience with it. Don't know how to fix it. I just gave that one to a friend and built me a Box of Rock clone.

[Bucksears]

I had the (semi) same experience with my Vox EXP II the other day. About to start cutting the wires on it to use the case for something else, and decided to plug it in for one last spin. It sounded awesome.
After I was done, I started pulling the JFETs, one at a time, and seeing what type they were. The next night, everything was that fizzy/gated misbiased sound.

On the upswing, the BSIAB II is sounding better. The only thing that has changed with my setup lately is that I'm usinga  BBE SupaCharger power supply.

[Jered]

  I know FET's with different part numbers (J201, 2N3819, etc) sound different. But I would think if you had two BSIAB's, both with all J201's from the same manuf. that the diiference you would hear between the two would come mainly from the resistor and capacitor tolerances, and how much the can vary.
  Jered

[jrc4558]

  I know FET's with different part numbers (J201, 2N3819, etc) sound different. But I would think if you had two BSIAB's, both with all J201's from the same manuf. that the diiference you would hear between the two would come mainly from the resistor and capacitor tolerances, and how much the can vary.
  Jered

Agreed. Also, since BSIAB uses µ-amp configuration for fets, the only one that needs to be biased really, is the Q5. So very true, 20% torerance of some capacitors can give to you or take from you the sound you like...