2 band Tonestack in BSIAB2 - Volume drop!

[juan_felt]

Hi guys!

I built the BSIAB2 from GGG (http://f.defaut.free.fr/photos/BSIAB2/bsiab_2_sc.gif), love the sound of it, but not very pleased with the tone control. So I decided to try adding a 2 Band tonestack where the Tone section is (between C9 and R17). I used the James from the Duncan Calculator.

I'm using the following values (James, in tone stack calculator):

R1: 100K
R2: 100K LOG
R3: 10K
R4:180K
R5:1M
R6:100K LOG

C1: 471
C2: 103
C3: 561
C4: 222
I can tweak the eq to make it sound KIND OF what I like, the problem is that it creates a massive loss of output volume.

Is there a way of doing this without that volume loss? Has anyone atempted to add a 2 (or even 3) band tonestack to a BSIAB2 succesfully?

Thanks!!!!

[GibsonGM]

Hi Juan,

Good idea!  BUT - there is a thing called "insertion loss" that's inherent in all passive devices.  Tone stacks (and other things) simply suck power out of your circuit!  They're not "free to run".   So, yes you can add any number of EQ stages to a BSIAB  BUT - you will get what you did (loss of vol) or worse - NO volume!

You can fix this by adding a "recovery stage" after your extra tone components, just before the output (volume) pot.  Search "recovery stage" for more, or look up "Fetzer Valve", which might offer something in the way of bringing the volume back.  Sort of a pain on an already-done board - you could run a line from the board to a smaller board to do this, tho, if you wanted. 

You can test this by running the BSIAB as-is, with volume all the way up, into a booster to see if that does what you want...you need a high input impedance and low output impedance after a tone stack....