Would you expect DSD to be quieter than PCM?

[mansr]

There are multiple factors at play here. Firstly, the PCM and DSD versions of the same track might inherently have different levels. This explains why the effect depends on the content. Secondly, the conversion to analogue in the DAC might not be level matched.

 

Here are a couple of test files, one PCM and one DSD. Both have a 1 kHz sine tone at -3 dBFS. In theory, they should play at the same level. If they don't, it's not necessarily a bad thing. It just means your DAC hasn't been tuned for this.

 

For example, on the iFi Nano, the output is 1.5 dB lower with DSD than with PCM.

dsd-test.zip

[mansr]

3 minutes ago, kumakuma said:

DSD is generally mastered 6 db lower than PCM.

That's a bit of a misconception. DSD defines the 0 dB level such that if a full-scale PCM signal is converted to DSD and low-pass filtered back to PCM, the resulting signal will be 6 dB lower. The reason for this is that the sigma-delta modulator isn't stable for large signals.

 

This does not mean that DSD is mastered lower. All it means is that the analogue voltage to digital value mapping uses a different scale. In fact, PCM uses many different scales. For instance, with 16-bit integer PCM the 0 dB level corresponds to a numerical value of 32767 while floating-point PCM (typically) encodes the same level as 1.0.