BSIAB with less gain and more open?

[mattpas]

Hey all,
I love the BSIAB but was wondering, what transistors would give it less gain and open the pedal up a bit more?
I would want to cut the gain a 1/4 to a 1/2 of the amount it currently has.

[aron]

What if you just put a resistor in series with R19 (drive pot)?  Between R6 and R19 try a 100K or 220K resistor. Disconnect C14 and maybe even C13 for more highs.

http://www.generalguitargadgets.com/pdf/ggg_bsiab2_sc.pdf

[John Lyons]

Either that or use all 2N5457s and leave it as it is.

John

[mattpas]

Either that or use all 2N5457s and leave it as it is.

John

John,
have you tried that?
What did you think?

[m-theory]

Either that or use all 2N5457s and leave it as it is.

That's a great place to start lowering gain.  To me, it sounds much more plexi-like, whereas the original circuit seems more JCM800-ish. 

You can also swap c5 w/530pf to open up the mids a bit more, and remove or adjust c10 and c13 to remove some low-end congestion, if need be.  I did this on mine on Ed's recommendation, and it worked beautifully for my tastes. 

It's important to note, though, that these things may not all be necessary to get you where you want to be.  It depends on your rig and your tastes.  I really like having all 2n5457's and both of those low end caps removed, but a buddy of mine tried it, didn't like it, and ended up putting the J201s back in and replacing one those two caps (not sure which one) wit a .068uf, and he's in nirvana with it now. 

[Dragonfly]

another option is to use a combo of J201's and MPF102's

I do like the sound of the 5457's though....

[mattpas]

I think I am going to do one with all 2N5457s.
That seems like it would be what i want.
I like the pedal but a bit less gain and more open is all I am really looking to do.
Thanks guys.

[m-theory]

I like the pedal but a bit less gain and more open is all I am really looking to do.

Less gain is what the 2n5457's will get you.  If you want "more open," you'll have to tinker a bit with those caps. 

[mattpas]

I like the pedal but a bit less gain and more open is all I am really looking to do.

Less gain is what the 2n5457's will get you.  If you want "more open," you'll have to tinker a bit with those caps. 

So you suggest leaving out C10 and C13, someone else suggested leaving out C13 and C14.
When you put all 2N5457s and left out C10 and C13 did you loose any sustain?

[m-theory]

You know something?  I just remember that this layout has changed fairly recently.  I built off the old GGG layout, so it may be different caps.  I'll have to look at the schematic and layout that I've got at home.  I believe they were .022 and .0022, though. 

Did I lose sustain?  No.  I lost the low end congestion and "crowding."

There were two things that I didn't care for in the original circuit:  1)  it was dark and congrested sounding to me, and 2)  when you turn up the tone control to try to get it to cut through the mix more, it can tend to get harsh. 

Removing the low pass caps seemed to be the ticket for eliminating the congestion, and changing the 470pf to 530pf was the ticket for bumping the mids just enough to cut through nicely.

I'd do the transistor swaps first though, and see what that does for you.  You might find that to be just exactly what you're looking for. 

[Quackzed]

as an alternative to swapping out fets, for lower gain you can make r14 lower (i used a 22k). to my ears, it reduces the high gain fizz and lowers the gain to about half. giving more of an overdrive feel, also seems to bump the low mids a bit which is nice for lower gain tone...i used all j201's and also omitted the gain pot cap (150p) because it made the low gain tones a bit more full (more bass).
I really recomend this method of reducing gain in this circuit (bsiab feels GOOD).
i used a switch to go from high gain to low gain by using a ---22k---56k-- in series to ground for r14 and using a spst switch with its leads around the 56k bypassing it for 22k or (22k+56k=)78k...

[John Lyons]

Quackzed
How does making R14 affect the overall volume of the pedal?
Seems that at 22K it would lower the gain but may not be able to have enough output level. (Possibly)

Also, the 150p cap across the hot and wiper is a treble bleed cap.
At lower drive settings you will get more treble bled though with this.
This is in contrast to what you were saying.

john

[Quackzed]

oops,  what i had meant to say was that REMOVING the 150 pf gave me more mids and a fuller low gain sound, as opposed to when it was in the circuit...
as far as  volume loss goes, it seems to reduce gain more than volume. it does reduce volume a bit but it is minimal, the gain reduction is quite noticable however, with 82k it feels high gain for me, with just 22k much of the high end 'crispy distortion is noticably less and feels more ampish?!! more oomph and less hash? not to say the high gain sound is too crispy (love it) but for lower gain tones i couldnt seem to get the ac/dc marshall rythem tone , it was still too edgy, this however did the trick!

[John Lyons]

Ok, thanks for the explanations. I would imagine that that last stage is being overdriven quite well, so lowering that 82K is bringing down the impedance and gain, which would ease up on the high end...

john

[Quackzed]

impedence... huh!  It did seem odd to me that the high end cleaned up a bit as well as the gain reduction... I even ran the .022/82k high pass filter through a calculator to see what i was doing by using 22k instead, found that i wass rolling off at @300 hz with the 22k while the 82k was rolling off at @ 80 hz. s0 i figured i was rolling off bass and thereby reducing gain, but what my ears were telling me was that i was also cleaning up the high end, which was odd. but a lower impedence reduces high end /bandwidth ? this must account for the less edgy sound i'm hearing. I like this 'lower gain' tone ALOT! but i'm afraid my understanding of what caused the change is a bit beyond me...
      initially i just used a 22k 56k in series cause it was close to 82k and i didn't have an 82k... then i had to poke around and clipp off the 56k just to see... a very happy accident... as i was looking for an easy way to get a less hotrodded marshal tone as well.

      thanks for the insight. hope i understood / didn't mangle what you were saying.

love this thing ! i play a twin reverb and never really played marshall stacks ... i don't know if the bsiab ii sounds just like a marshall, but it sounds great to me!

[ubersam]

Try increasing the size of the source resistors R3 & R10, maybe even R15. That should lower the gain of the circuit. The only drawback is that it might change the character of the circuit too much, as in, it wouldn't sound like a BSIAB2 anymore. But then again, that might be what you are looking for.