bsiab - all 2n5457 no j201

[numpty]

hi
  i understand that you can use exchange the two j201 for 2n5457 for a more vintage less aggressive sound, is rebiasing required? if so what are the recommended value(s)? that is,  what other components, if any do you change? and also what voltages should you be seeing at the gate, source and drain of the exchanged 2n5457
thanks

[MKB]

I just finished a BSIABII with all 2N5457's, I installed them with no biasing changes at all.  The tonal changes between swapping these with J201's was the 2N5457's had less gain and clearer highs.  I do not recall any significant voltage changes.  The BSIABII with all 2N5457's still has a lot of gain available, but cleans up a bit better.  The J201 version is almost "too much of a good thing".

[Ed G.]

That's the beauty of some of these designs, you can pop in different transistors and get different tones.
I like some things about 2n5457s and some things about J201's. I really like 2n5458s for good clear fat low-gain tones, J201s are fat and smooth and rich sounding, kind of like a good milkshake. I've always looked for gainy yet tight sounds, so I'm always experimenting, I use sockets on my pedal for the transistors.

[JimRayden]

No biasing required on Q1, Q2, Q3 and Q4. They should bias right up on their own. Only Q5 is manually biasable by the means of the trim pot.

---------
Jimbo

[John Lyons]

Good to know, I'll try out these sugestions!

John

[numpty]

thanks for all that info, all the jfets have sockets in my bsiab, so any changes i make will be reversable without the possibility of damage.

[Steben]

Well I have 2N5459's around. They seem even less gain, no?
Maybe using a J201 stage and a 2N5459 stage can be nice too. Should still give a full gain at extreme settings.
I would like to bring the gain to plexi levels maybe with a booster in front of the BSIAB.