how do i get more gain from this circuit?

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how do i get more gain from this circuit?

Sensei Tim
I built up a 3 band bass preamp following the EBMM stringray schematic:



The problem is when i have the volume set to max i have slightly less than unity output. I get it that you won't notice this if it's wired in a bass and you can't turn it off, but since this is in a pedal, the volume drop is noticeable.

I'm trying to figure out how to coax some more gain from the opamps, but i;m not seeing a feedback resistor to change on the IC on the left and i'm not really sure what i would do with the IC on the right.

I've already tried dropping the 130k resistor on pin 2 down to about 47 but it didn't really do much.  Now i'm thinking about the 10k/560k on pin 3?  if i drop the 560k down will that increase the voltage that comes onto the signal in pin 3 and make it louder?


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Re: how do i get more gain from this circuit?

Frank_NH
I would put another gain stage after the active tone stack and before the output pot.  You could a simple JFET stage with a clean gain of 2 to 4 (biased using suitable drain and source resistors).  You could also use a third op amp.  
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Re: how do i get more gain from this circuit?

Sensei Tim
Yeah I figured I could always add a boost. It there should be a way to use that first op amp stage to get some gain.  I've got some ideas that il going to try this weekend and see if they work.

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Re: how do i get more gain from this circuit?

Frank_NH
You could always turn that first stage into a gain stage, but you might change the existing input filtering somewhat.  This would be easy enough to test out on a breadboard.