I modified the circuit of the battery amp to put the volume control before the first stage like the original FET version of the amp (one of the first posts). It really doesn’t sound that different – It just allows you to have really high output input sources without overdriving the first stage. It is very easy to modify the original board layout to do this. On the final stage, I also modify some values because of the altered gain distribution.
Here Is The New Schematic showing what needs to be modified:
https://circuitsaladdotcom.files.wordpress.com/2013/05/portaamp3b.gif
if you compare to the last version – its not that different.
Here is jazz demo with some compression from my simple opto-compressor and the amp set with a little mid size room reverb and mid way settings on the Bass, Treble and Presence. The guitar is a cheap beater electric that cost me $150.00. It is always fun to see if you can good sound out of crappy guitars!
https://circuitsaladdotcom.files.wordpress.com/2013/05/night-and-day-with-comp.mp3
Note: In the this schematic and layout below, I changed one of the select lines for the FV-1 to use a different reverb algorithm – not a big deal – I just like it a little more than the original.
Here is a new board layout that requires no modification and reflects the new schematic exactly:
http://www.fileswap.com/dl/v1TrMfdse/
Here is the schematic as shown above but without any references to modification:
https://circuitsaladdotcom.files.wordpress.com/2013/05/portaamp3bfinal.gif
Circuit Salad 
Hi Ray. Have you released the circuit board patterns for this version yet? I downloaded the board for the Fet version but thought I’d wait for this one.
Hey Yes I have that layout posted – I just updated my most recent post to provide the a link to the Layout of the version I like best( there are a couple variations) so go back and look and you should see it.
Ray
On Mon, May 20, 2013 at 8:18 PM, Circuit Salad
Hi Ray,
Can you steer my in the right direction in relation to pot tapers for the Battery Amp?
I assume that the Volume pot should be a log/audio taper? But what about the tone, presence, and reverb pots??
Also, if I wanted to take up the suggestion of subbing R29 with a pot for adjustable gain, what value would you suggest (and what taper)?
Thanks for another great project!
I think I used linear pots for everything else. A 5K pot should work in place of R29. This amp works fine but over all I a happier with the stomp amp configuration…Have you looked at that? The tone stack is more versatile and it is ultra quiet(noise) You could make a hybrid using the op amp input and tone stack and then just pickup at Q3 with the darlington circuit. If I can assist you – let me know