I've been using my USB3 for a year or so now and very pleased with it generally. I have to be careful to do things slowly when starting the car, otherwise it loses connection to the H/U, but it's workable.
I notice however that I have my volume cranked to near maximum for normal listening, and the signal from USB3 via bluetooth and USB is significantly attenuated compared to the built in CD player. I realise this is likely due to design of the H/U.
Is there anything I can do (not scared of circuit level mods) to increase the analog output level (even a few dB would help) of the USB3?