That's what I like about Audio-GD. They have good products and are small enough that you can
get that one on one raport with them when you need help.
Well I hadn't thought of that. Asking technical information from a manufacturer and expecting an answer seems like an alien idea.
But it worked! I received an answer, telling me which resistors to change, to what value, and what the result will be.
There's 8 2202 surface mount resistors in a line of 16 resistors between the dual DACs and the dual relays. 2202 is 22k 1%. Changing these with 47k resistors will lower the gain by 7dB.
Here's the line of resistors in question.
The other 8 resistors are 5.6k. They alternate, so there's 22k, 5k6, 22k, 5k6... etc. I'm guessing the 5k6 are for the high gain and the 22k for the low gain. Edit : Just received an email confirming the 5k6 are for the high gain.
So now all I need are 8 47k resistors in 1206 package. Changing these will be quite a challenge.