Class D amp settings

[PWRmx24]

Getting ready to set up my Class D Buckeye Purifi amp. There's low, med, high gain settings on the back. Any thoughts on how to determine best gain setting?

 

[PWRmx24]

My Rotel RSP-1570 pre-amp manual says: s/n ratio (IHF A-weighted) 95 db (analog bypass) 92 db (Dolby Digital, dts) 0dBFs; input sensitivity/impedence: Line Level 200 mV/100k ohms; Pre-amp Output Level/Output Impedence: 1.0V/1k ohms; Contour (LF/HF) +- 6 dB at 50 Hz/15kHz. The amp spec says s/n 137dB; 4 ohm 25dB/2.2Vrms (high), 20dB/3.9Vms (med), 15dB/6.9Vrms (low). Is it better to let the amp or the pre-amp do the "gaining"? I guess it depends if the s/n gets worse as you turn the knob on the pre-amp???

 

[Steve81]

Hello there. The goal is mostly to find the balance between the preamps clean output capability and system noise while achieving full output from your amp. I’d start with high gain, and move down to medium and see how noise levels compare. If no appreciable difference, don’t sweat it.

 

[Golfx]

Hello there. The goal is mostly to find the balance between the preamps clean output capability and system noise while achieving full output from your amp. I’d start with high gain, and move down to medium and see how noise levels compare. If no appreciable difference, don’t sweat it.

I agree with this.
Theoretically, high gain “may” let you hear hiss from your speakers (from the preamp’s electronics). If so, try the lower setting until you hear less or no hiss.
I use high gain as I can not hear any hiss.