How to bypass transistor(s) in BSIAB2 - or any similar circuit?

[kevinabb]

I've built two BSIAB2 boxes, which are killer and sound very similar to each other.  I'm doing various mods to one of them, and want to install toggle switches that will bypass the second stage (switch 1) or the final stage (switch 2). Does anyone know, what is the minimum I would have to do to safely bypass these stages (one at a time, not both together)?

I could try a crude bypass of the final stage - which has only one transistor - by simply using a 3PDT switch to remove each of the transistor's leads from the circuit. But I have a feeling that might not be the correct way to do things. And the second stage, a two-transistor pair, is a much more complicated situation.

Any help is greatly appreciated.  I've done extensive searches in forums & on Google and haven't been able to make headway.

[petemoore]

  True bypass switch wiring.
  I've never asked or run a jumper across the in/out of a stage before.

[blacKtearZ]

You dont need to disconnect the transistor leads in order to bypass a stage. To bypass second stage, just use a DPDT to connect drive pot middle lug to the input cap of third stage i.e C12 (0.022uf in GGG schematic) which will bypass second stage.
for third stage, again use a DPDT to connect output of stage 2 (i.e C12  0.022uf) to input of tonestack (C8/R7 junction).
I had thought about trying that to create a Crunch/Lead switch in my Bsiab2 but never got around to doing it. Lemme know how it goes.

[Quackzed]

i've done this, its a good idea.
basically, the bsiab is 2 mini booster stages into a single transistor stage, so if you bypass the second and third stages, you have a booster.
if you bypass just the third stage you have a dirty booster. and bypassing no stage is distortion.  pretty versitile.
i believe i just used a spst jumper wire, but a dpdt is a more effective way to 'bypass' a stage.
just find the 2 points that contain the stage you want to omit, and treat them like an individual circut. then wire it for true bypass.

[caspercody]

Look at Texas Brownie schematic. He used a spdt switch to bypass one of the jfet stages.

[kevinabb]

Thanks for the help, guys.  I will pursue all of these suggestion.  blacKtearZ, thanks a bunch for the detailed explanation. That's exactly what I was hoping someone could help me with.  I know there'sno point in bypassing all three legs of a transistor. but my recollection of which point(s) to bypass fell out of my brain long, long ago.

I'll report back on my progress, but it'll take me a bit as I broke on of the 5457's while I was playing around with transistor combos.  I now have a 201 & a 5457 in stage one.  Not a bad substitute, but it defintely adds a bit of grit that I don't want or need.  BTW - if you want a bit of a grittier sound from your BSIAB, that mmight be a good way to do it. Obviously YMMV, especially given the inconsistencies of commercial-grade transistors, FETs specifically.