I would not think the DAC is the place for adjustment. You should be delivering a pristine raw signal from any device, and then adjust tone with your pre-amp or processor, or an EQ. Many processors/Pre-amp have ways of adjusting tone controls, and may be in software in the unit, not physical knobs. If not there are EQ devices that may help determine if it's a good solution or at least improvement for you. If it were me I'd grab a cheap EQ and play around (pawn shop?) and then decide if a better one may be worth the investment. Past that there are a lot of devices to change the tone with some DSP features, but no need to go really high tech until you determine if tweaking the tone controls would help.