BSIAB II Volume Roll Off Treble increases

[erick4x4]

I really like rolling my guitar volume off on fuzzes when I want to clean up, but I notice that on the BSIAB when I roll off the volume it does clean up but the highs are really pronounced (or the lows are missing).

What causes this, and can I adjust anything to fix this?

The circuit is only modified by using all 2n5457's other than that it is stock.

Any ideas?

[snoof]

you may have a cap across your gtr vol pot that is allowing highs to pass around the pot as it's turned down.  this might be perceived as a high freq boost as you turn the vol down.  does this prob happen with other OD's, or with gtr straight to the amp??

[erick4x4]

No only on this 1 circuit. That's why its so strong. Typically when you roll off volume on the guitar it gets muddier.

My guess it that when I don't push the first gain stage very hard it cuts off too much lows. Should I increase the cap between the 2 stages? Or will that get it too muddy?

[snoof]

I raised C2 to .1u on mine and it helped w/ the bass cut.  Try searching "bsiab mod" for other suggestions.

[erick4x4]

My problem is I feel like it can be a touch dark when its cranked distortion, so I am worried that C2 would make the cranked wound really muddy? Or maybe not?

No other tips/tricks to get the bass more even whether it is hot or low input?

[John Lyons]

Not nec. the problem but the cap across the gain pot is a treble bleed cap. Try removing this and see what that does.
What the cap does normally is increase treble at lower gain settings and it is esentially out of the circuit at high gains.
This may help.
Try C2 as well, it's hard to say if it will get the job done because the signal into the pedal from the guitar is what is changing the tone.

John

[snoof]

But he says that rolling the gtr vol down has a percieved treb increase, not the gain pot.  Might rolling the gtr vol down change the RC filter comprised of the gtr vol pot and C1??  Would moving C1 after R1 prevent this from happening??

[John Lyons]

Hmm... not sure.
As far as  know C1 is a treble cut/shunt to ground which would kill some of the high treble nasties and hash that could get in the circuit's input and boosted by the high gain of the circuit. I don't think that would make any difference as even with the guitars volume rolled off the cap is still shunting high frequencies to ground.
We need someone smarter than me to figure this out!!

John