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Confused about DSD playback on Mac

Hello!

I am new to the world of hi-res audio and a new owner of TOPPING D90 III DAC. 

When I use TASCAM Hi-Res Editor on a DSD64 sample (01 - David Elias - The Window - Vision of Her (DSD64).dsf) the editor correctly identifies the audio file as DSD/DFS 2.8MHz 1bit stereo. It changes the Audio Device for the DAC on my Mac to 2ch 24 bit 176.4khz. The DAC on its display shows 2.82MHz DSD. This seems to confirm a native DSD64 playback. 

I am confused about the DAC's settings in the Device Audio app on the Mac,  2ch 24 bit 176.4khz. How does this correlate to DSD64?

In contrast, when I use Kodi with a SACD ISO support plugging, playing the same file, it set's DAC's Audio Device to 2ch 32 bit 352.8 kHz and the DAC shows on its screen 352.8 kHzPCM. 

I am confused where 2ch 32 bit 352.8 kHz comes from. 

Any help would be appreciated! Thank you. 

ooz
erik_squires
17,557 posts
 

I’m not quite sure what’s going on with your setup but you may be getting "DSD over PCM."  This is a well-recognized workaround when protocols won’t otherwise recognize DSD.  For instance, you can use S/PDIF which was originally PCM-only to transmit DSD, but only up to a certain resolution. 

In other words, your Mac thinks it's moving PCM data but it's really DSD in a PCM wrapper.  Your DAC see it and decodes it as DSD. 

ooz OP
1 posts
 

To add more to my confusion: 

I am trying Tidal streaming 24 bit 192kHz (calculated to 9,144 kbps).
The Audio Devices on the Mac shows 2ch 32 bit 96kHz (calculated to 6,144 kbps).
The DAC shows 96kHz PCM (1 bit so 96 kbps).

The automatically selected  2ch 32 bit 96kHz seems too low for the 24 bit 192kHz stream. 

erik_squires
17,557 posts
 

Not every tidal source will be 24/192.  But I'm pretty sure you are getting DoP as it's called for your DSD sources.  

Your math is off.  

A 24 bit/96kHz PCM signal is 96,000 x 24 x 2 ~= 4.6 Megabits per second

Low rate DSD = 2.8224 megabits per channel per second, so almost 6 megabits/second for stereo. 

176.4 kHz (4x 44100) * 24 * 2 ~= 8.4 megabits per second total. 

So, a 176.4/24 bit PCM wrapper around DSD could easily carry standard rate DSD

carousel's avatar
carousel
31 posts
 

Yup, to borrow from PC Mag: „DoP (DSD over PCM)enables high-resolution DSD audio playback on macOS by encapsulating DSD data into 176.4/24 PCM frames, as macOS does not natively support raw DSD transport. A DoP-compatible USB DAC is required to unpack this data and reconstruct the original DSD stream.“

Sounds though like maybe the MIDI setting on you Mac for your DAC is downscaling from 192 to 96K. Make sure Mac settings are maxed and/or set Exclusive mode in Tidal.

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