Is it of any benefit to use a software upsampler (Sox Resampler) to upsample, let's say from 44100 to higher or 88 100 / 96 000 to higher? Btw, I use your DAC 2 HGC. :-) - Vjekoslav
In some cases, upsampling will improve the output of your D/A converter. The low-pass filters incorporated into the upsampling process will essentially replace the filters in your D/A converter. If the upsampling software has better filters than those built into the D/A, then you may experience an improvement.
But, the upsampling will usually add distortion if the original file has intersample overs. Most commercial recordings have intersample overs. Distortion due to overloads can be prevented if you decrease the signal level by 3.5 dB before upsampling. If you don't reduce the gain before processing, the damage done by intersample overs will be far outweigh any advantages provided by the upsampling!
We actually use this technique in our DAC2 converters, so there would be no need to apply this processing before feeding a Benchmark DAC. We also drop the gain by 3.5 dB before upsampling.
Don't upsample you audio files if you are using a Benchmark DAC, there is no need to do this twice. If you want to upsample files for use with other DACs, reduce the gain by 3.5 dB before processing.