I'm looking for detailed instructions for an audio mod for the DSP 40 which
is supposed to increase the volume quite a bit. According to the only online
source I could find, this requires soldering jumpers over R54 and R57. I
opened my unit up and could not find these two resistors.
If any of you have performed this mod, could you let us know how you did it?

Have you seen this page?

www.geocities.com/n2cbu/DSP40/DSP40MOD.htm

No, I haven't done anything to mine yet. I have three so thought I might
sacrifice one when time allows.

Rob Mills ~~~