BSIAB2 adjustment I'm happy with

[Bucksears]

Ever since I built it, I've been very happy with the amount, range and quality of gain the BSIAB2 has, as well as the volume and bass. Like many others, I've felt that the BSIAB2 is too dark. Even when you max out the tone, it winds up being harsh because it zaps the bass and boosts part of the mids (to my ears, anyway). If a pedal needs an extra EQ unit to get it to sound right, I won't use it; call me crazy, but it's just not convenient.
Today I think I finally found a config/tweak of the BSIAB2 that works for me.
1) I'm using all 2N5457 transistors
2) I removed the .022uF cap from the second low-pass filter.

This gave the 'presence' that I'm looking for, but it's pretty much a 'sweet spot' that keeps the bass, yet lets enough highs through to bite nicely. It very much lives up to its name, nailing a nice 'brown sound' with a slightly-below-flat midrange sound.

While I'm at it, what does the resistor do in a low-pass filter? I'm using 10k res/.022uf/10k res. right now; what would removing the 2nd 10k resistor do?

- Buck

[MetalGuy]

By removing the second cap you eliminate the second pow pass filter and you're getting more highs now.
I don't know why those filters are there at all - maybe if you want to plug directly into a mixer? I'm plugging directly into the FX return of my tube amps -  I removed these filters from my pedal because  the sound I was getting with them was horrible.

[powerplayj]

Bucksears,

What cap number (on the GGG layout) is that for those like me who cannot differentiate where the low pass filter is?

http://www.generalguitargadgets.com/diagrams/bsiab_2_lo.gif

Thanks,

Jason

[Bucksears]

I removed C14.
I don't want to remove both low pass filters, as I like SOME control over the highs, but this is setup is nice. I might play with it more if I'm bored.

- Buck

[DuncanM]

The low pass filter is at the very end - the two 10k resistors and the two .0022u caps (R17 & 18, C13 & 14)

Roughly speaking,
these are set to roll off the high end and with both sections in the circuit the rolloff will be 6dB down at 7.2kHz and continue at 12dB per octave (i.e. 12-15dB down at 15kHz)
Removing C14 will change the filter from a two stage filter to a single stage - now only 3dB down at 7.2kHz and rolling off at 6dB per octave (so only 6-9dB down at 15kHz).
So more high frequencies above 7kHz...

Removing R18 from the circuit will do little for the tone but will give a touch more volume - with the resistor in the circuit you effectively have a 110k pot which can only go up to 100k.... You should get an extra 0.8dB without R18.....

That's my reading of the circuit anyhow...

[powerplayj]

Thanks guys....now if you could remove a bit of the hum incurred at high gain I'd be set!!!!!!!!