MQA, grouped zones, and bit-perfect playback

[Jim_Austin]

Hello Roon experts, I have an observation and a question. I’ve read–and heard, and believe–that when zones are grouped, bit-perfect playback is inhibited because of the necessity of achieving tight synchronization between the (two) zones. I’ve also long thought that if an MQA-encoded DAC can decode MQA, that’s an indication that the DAC is receiving bit-perfect data.

I’ve just grouped two zones, sending the output to two different MQA-enabled DACs, and both indicate that they are decoding MQA.

That’s wonderful–but can someone please help me understand the apparent contradiction?

Thanks.

[Chrislayeruk (Chris)]

Clearly what you have read is incorrect with regard to Roon. Great news.

[Henry_McLeod (Henry)]

It would take a lot to throw stuff so far out of sync that bit perfection could not be achieved. My guess is a stable network and good quality RAAT endpoints would be well within the capability of Roon to maintain bit perfect playback. Note though that my understanding is that bit perfection is not a requirement of MQA playback. You only need to ensure the MQA headers are intact. Hence the ability to apply DSP to a MQA signal and still have the DAC apply the necessary unfold.

[joel]

Note though that my understanding is that bit perfection is not a requirement of MQA playback. You only need to ensure the MQA headers are intact.

You have it back-to-front. The headers are only actually informational and can be stripped (I’ve tried it). OTOH, the critical information is buried in the lowest bits of the audio, so bit perfect playback is critical for decoding/rendering.

[Jim_Austin]

OTOH, the critical information is buried in the lowest bits of the audio, so bit perfect playback is critical for decoding/rendering.

Thanks Joel. Seems obvious, but just to confirm: Is it appropriate to consider MQA playback as a rigorous test for bit-perfect playback?

My thanks, too, to @Henry_McLeod and @Chrislayeruk.

Jim

[joel]

Yes, as good as anything else I can think of offhand. I recall that a DTS-CD stream rip used to be the thing to use.

[Tom_K (Tom Keenan)]

When I play an MQA recording, with all DSP filters bypassed (and no headroom management or sample rate conversion), Roon displays the signal path as “enhanced”, not “lossless”. If it is bit perfect, why isn’t it characterized as “lossless”? Maybe I’m not understanding a difference between bit-perfect and lossless? Or did I get something wrong in the settings?

[ged_hickman1]

If your DAC is reporting back to roon that it is doing “enhanced” MQA decoding then that triggers the enhanced. If you switch DAC settings to say it is not mqa capable the same track will show as lossless.

[philr]

hen I play an MQA recording, with all DSP filters bypassed (and no headroom management or sample rate conversion), Roon displays the signal path as “enhanced”, not “lossless”.

There are a number of threads discussing this, for example.

Lumin MQA Settings

That is correct, and it is Roon Labs’ decision. Last time I asked, Roon Labs consider the MQA rendering (second stage of the MQA decoding) to be Enhanced.

[wklie (Peter Lie)]

Is it appropriate to consider MQA playback as a rigorous test for bit-perfect playback?

With the exception that truncation to 16-bit is allowed, which is a feature.

As for the contradiction, do you have Roon perform MQA Core decoding (as shown in signal path)? I guess this makes an important difference.

[Henry_McLeod (Henry)]

Thank you for that clarification Joel. Every day is a school day!

[Jim_Austin]

As for the contradiction, do you have Roon perform MQA Core decoding (as shown in signal path)? I guess this makes an important difference.

No.

Cheers,
Jim

[wklie (Peter Lie)]

My understanding is this: if the grouped DAC cannot dynamically tune its clock (like most DAC and our products) outside 44.1/48kHz multiples, especially with the DAC handling full decoding instead of rendering only, MQA integrity will be affected momentarily when Roon tries to sync the grouped zone slave. However, even if the MQA authentication fails momentarily it’s very easy to be missed as it’s re-authenticated very soon unless you’re staring at the MQA LED or front panel for the whole time.

Further details in this thread:

Grouped Playback and MQA

If you’re doing clock drift compensation in the digital domain, and continuously–yes, it’s unavoidable. Some forms of drift compensation (for example, bending the clock rates in the analog domain) do not disturb MQA. Both approaches exist in the Roon Ready ecosystem, however with USB DACs, we are stuck doing things in the digital domain like you’ve observed. With 2 MQA DACs grouped, the clock master would play bit-perfect and the second DAC would compensate like you’ve seen. If you have just …

[Jim_Austin]

However, even if the MQA authentication fails momentarily it’s very easy to be missed as it’s re-authenticated very soon unless you’re staring at the MQA LED or front panel for the whole time.

Pretty much the situation. Cheers.