My experience with Bifrost 2 (230V version) has been very disappointing. I had to return two units. The first unit exhibited random issues somewhere within the DAC where the audio output would appear as if a very strong low pass or a comb-like filter was applied to the output. The issue would...

Try decreasing the volume on your amplifier and increasing the gain on the NFB (low/high gain also affects the pre-amp output, at least on the variable setting). Otherwise, use the fixed level output mode and alter the volume on the SMSL.   SMSL's power supply might also be affecting other...

It's probably picking up noise from the computer via USB. Try disconnecting the USB cable, in case the hiss goes away, you might want to try setting up a optical connection from the PC to the DAC (if possible).

^^ FWIW, my problem is a ground loop. Since my stereo amp is a DIY project, disconnecting the main's earth connection solves the USB noise problem. I guess my next USB DAC will have to be balanced. :)

My NFB-11 setup for speakers: PC -> USB -> NFB-11 -> RCA preouts -> XLR inputs on a stereo Hypex amp. With this setup, I get a slight PC interference noise from the speakers that changes with varying loads on the computer - typical crappy PC sound. The moment I disconnect the USB cable the...