DSP Engine only outputs 16 bit?

As of 12/22/2017 I’m running the latest versions of Windows 64-bit roon core 1.4 (build 294) to a PS Audio PerfectWave DAC with Bridge II (also at the latest versions). When playing hi-res files (96-24) the DAC reports 16-bit WAV if the DSP Engine or volume leveling is enabled. If DSP is disabled the DAC reports 24 bit WAV as expected. I would not expect the bit depth to be degraded when using DSP. I’m not sure roon 1.3 did this or not.

Can you provide a screenshot of the Signal Path when issue is happening and also screenshot of your DSP settings. Thanks

Simplest case: No DSP Engine, just switching Volume Leveling from OFF to AUTO.

Volume Leveling OFF


Turn Volume Leveling ON


The PS Audio DirectStream figures out the bit depth and sample rate on its own. It does not rely on the source to tell it what those values are. So, if a 24 bit or 32 bit track only contain zeroes in bits 17 to 24 or 32, the DAC will display them as 16 bit files. I can’t tell you why the original unmanipulated track shows as 24 bits. But, after manipulation that track is down to 16 bits plus a bunch of zeroes from bits 17 to 32.

Hmm, that is an interesting one. Ultimately, Roon’s Brian and/or PS Audio’s Ted Smith may need to chime in.

But from what I can diagnose, Roon is outputting 32 bit integer over RAAT to the Bridge II. That 32 bit integer output is converted and dithered down from the 64 bit floating point internal precision at which Roon DSP operates. Provided that 32 bit output is integer, not floating point and is dithered, it should not be just zero padded out to 32 bit. Then again, few DACs display received bit depth – be that total logical or actual undithered bit depth – so this discrepancy does not rear its head very often.

As an interim solution in Roon, I would try changing the Device Setup > Playback > Max Bits Per Sample (PCM) to 24 bit – if that setting is available. Then, check both the Roon signal path and PS Audio bit depth display. For whatever reason, Roon to PS Audio over RAAT at 32 bit may be hitting a snag.


Thanks, Andrew. Forcing 24 bit maximum bit depth output resolved the display issue.

The PS Audio Bridge was also recently updated, and I don’t know if the issue existed before since I rarely look at the DAC display. I also wasn’t doing any critical listening and can’t say if there ever was any loss of sound quality.

We are definitely sending >16bits via RAAT to the device.

I did a quick check with a DirectStream here and am not seeing this symptom. @eric is going to repeat the test with a PerfectWave and see if it gives different results.