BUG: MQA streams only start playing audible output in Fixed volume mode
Answered
Hi!
I get no audible sound through the digital output of Bluesound Node when playing MQA content controlled by Tidal Connect and using external DAC (Technics SU-MA10 1-bit-streaming, not MQA certified, max 48 kHz) - if at the same time I want the BluOS app volume control available.
1) With Bluesound Node audio setting Fixed Volume off (requiring External MQA-DAC off) and selecting CD quality stream from Tidal Connect, playback will start and provide audio signal that is accepted by the external DAC through digital out (toslink reporting 44.1 kHz locked sampling frequency). Music is audible from speakers and the BluOS app volume control is available as expected.
2) However, with the same Bluesound audio settings as in 1) but selecting MQA quality stream the playback will indeed indicate it has started, but the system does NOT provide any audible music = quiet! The external DAC will not lock to any sampling frequency while the BluOS app reports MQA quality stream playing.
3) Suprisingly, with Bluesound Node audio setting instead set to Fixed Volume on and External MQA-DAC on and when selecting MQA quality stream the playback starts and provides audible music! The external DAC will lock to 48 kHz sampling frequency and the BluOS app reports HR quality stream (as the external DAC is not authorized for MQA it shows only HR I presume). Unfortunatly, in this mode I have no volume control available.
At this moment one could argue it has something to do with the old external DAC device being incompatible with the digital output of the Bluesound Node if not using External MQA-DAC on...
Not quite so!
4) After starting playback of MQA content according to 3) and changing back the settings of External MQA-DAC to off and Fixed Volume to off while stream is still playing, the device directly makes the the volume control available, and working! The BluOS app still reports HR quality stream playing.
So, the behaviour of 4) suggests there must be a bug in the digital signal handshaking of MQA content from the Bluesound Node to external DACs (only not MQA-certified?), which does not allow MQA content to initiate playback when Fixed Volume setting is off as in 2).
I want to be able to play MQA content displayed as HR quality while still having the function of the BluOS app volume control.
Has anyone else confirmed this? Can Blousound team confirm this as a bug?
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Official comment
This is not a bug - this is a requirement for MQA when using an external DAC. Please see; https://support1.bluesound.com/hc/en-us/articles/115006191908
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Thanks for the reply Tony.
I have read your linked post carefully, and cannot see how the reported bluesound behaviour of point 4) follows MQA requirements.
Sorry for my long post, but if you read it carefully you will note that HR playback indeed works for MQA content if started with Fixed volume and External MQA-DAC are enabled, and then continues to work during playback when both are disabled (allowing volume control), but not the other way around.- I'm not requesting MQA content to play reported as MQA on non-certified DAC.
- What I'm requesting is that MQA content should play reported as HR stream on non-certified DAC, indepentent on the setting of Fixed volume and External MQA-DAC.
- In my understanding the MQA standard should be backwards compatible, meaning that if an external non-certified DAC gets MQA content it should play HR-quality or CD-quality stream, in that order depending on what the DAC supports.
What works:
MQA content will start playing reported as HR when Fixed volume and External MQA-DAC is enabled.
What does not work:
MQA content will start playing without any sound (reported as MQA) when Fixed volume and External MQA-DAC is disabled!
Somehow, when External MQA-DAC is disabled is seems the NODE defaults to some digital output format that gives inaudible stream to my external DAC. When External MQA-DAC is enabled the NODE determines a compatible digital output format reported as HR stream! I can trick the NODE to provide audible sound in the former case by starting playback in external mode and then switch back during playback.0 -
When MQA is not enabled, your NODE will play a single unfold up to 24/96. I would contact your external DAC manufacturer if you are not receiving audio.
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Thank you for your patience.
According to both of you, with external MQA-DAC disabled the internal MQA decoder in the NODE will give out up to 24 bit/96 kHz (performing first unfold) when playing MQA content. And it may well be so that my old external DAC does not support 24/96. No sound. Too bad. BluOS app reporting MQA authenticated stream and volume control available.
Because MQA stream is backwards compatible (no unfolding), when I have external MQA-DAC enabled (passthrough MQA decoder in NODE) my old external DAC will play audio at the highest possible quality it supports, which is 48 kHz, possibly 24 bit. Sound coming out! All fine. BluOS app reporting HR quality (because higher than CD quality 16/44.1 but not authenticated MQA), unfortunatly volume control unavailable.
My problem is then that you say "up to" 24/96. Does this mean that the NODE decoder can in principle provide also 24/48 or 16/48 digital PCM output, i.e. still HR quality, being much better than CD quality?
Using MQA passthrough the external DAC unarguably plays HR quality fine! Maybe limited to 24/48 and not 24/96, but still... So how do I get the Blusound NODE decoder to provide anything lower than 24/96?
If 24/96 is the lowest possible, my only conlusion is that the Bluesound NODE does not support external DACs which has maximum quality lower than 24/96! Is that a sensible choice mode?
So dispite my DAC being old it can still extract HR quality from raw MQA stream but not play decoded output from the NODE...
Is perhaps a setting for low HR (24/48 or 16/48) output in the NODE decoder simply what I am missing?
Will not use analogue, tested too noisy, thanks.
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Ok, too complex for a guy who bailed out from a PhD in audio coding and went into quantum physics instead. :-)
Still, all MQA content I have found on Tidal play nicely on my external DAC at HR quality using pass-through of NODEs MQA decoder. Don’t see why it would need resampling. The old DAC sort of handles higher audio quality by itself from undecoded MQA better than the combination NODEs MQA decoder and old DAC. If there where just feedback information about signal resolution from external DAC I suppose we would not have this problem as the NODE could then decide to provide unfolded or partly folded data whichever highest the external DAC supports.
Now that we have come this far...
My issue in the first place is the missing volume control in BluOS app (requires fixed volume to be disabled) while still having external MQA-DAC enabled!
If I can trick the BluOS app into providing a volume control despite playing through external MQA, simply by starting to play a MQA stream first with external MQA decoder enabled and then switching to disabled while playing - then surely, it must be possible to provide the BluOS app with a volume control at the same time external MQA-DAC is constantly enabled?
I have proved it is feasible. Its annoying however, to enable/disable external MQA at the start of each MQA stream being played.
Thoughts?
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That would really be a step back from my Squeezebox which also has a display, but at least give me exercise.
@Tony: Can anyone at Bluesound comment on why the volume control is not available in external MQA mode? It seems I have proven it's not a technological limitation since I can trick the NODE into providing a volume control simply by disabling external MQA while the stream is playing!
Please implement this feature if possible. External MQA seems too restricting otherwise.0 -
If your external DAC is NOT MQA compatible - you are not getting MQA out of it.
If you have volume control is enabled, you are not getting MQA.
Please see www.mqa.co.uk for more details on how MQA works.
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My external DAC is not MQA certified, yes! BUT with MQA content I will still get HR (high resolution) streams playing in the DAC according to what both the NODE and the DAC reports to me. Because MQA is backwards compatible I'm happy with having external MQA-DAC enabled. This was the first part.
Regarding the second part, it does not answer my question: Why cannot the volume control still be made available even though I enable passthrough NODE decoder (=external MQA-DAC enabled)?
There seems to be no reason for this!
I repeat: I can trick the BluOS app into giving me a volume control simply by disabling both external MQA and fixed volume while the HR stream is playing, and I still get sound out!
It is very difficult to explain the situation more clearly. The other way around:
Why cannot fixed volume be disabled and external MQA-DAC be enabled at the same time?0 -
If you adjust the audio before (changing volume) before the final decode in the MQA chain, (the external DAC), you are compromising and thus technically distorting the intended audio output of the content. This is the Quality Authenticated portion of Master Quality Authenticated. This is all documented in the link I posted.
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I was suspecting that. But since the NODE recognizes that my DAC is not capable of MQA authentication and accuratetly reports HR stream instead, a "compromised" output (changing volume) should formally not be a problem right.
So I have discovered an unintended quirk in the BluOS app I suppose?
In order to allow volume control together with external DACs I'm suggesting a feature where any stream (including MQA) is bypassed in raw to external DAC without the first unfold being made by NODE decoder and performing no check for certified MQA-DAC (and hence not MQA authenticated if not, perhaps, first unfold is made by external DAC itself). This would make the NODE device truely backwards compatible by supporting DACs which accept backwards compatible MQA streams but not 24/96 streams.
To implement this, would it make sense to separate the current audio setting "external MQA-DAC" into two new settings "external DAC" and "certified MQA" ?
- Enabled setting "certified MQA" would require fixed volume if "external DAC" is also enabled (currently "external MQA-DAC" enabled).
- Disabled setting "external DAC" would allow volume control by automatically enabling "certified MQA" (currently "external MQA-DAC" disabled).
- Enabled setting "external DAC" would also allow volume control as long as "certified MQA" is disabled (combination not currently available).
I think I've already proved it is technically possible and should not violate MQA specifications. Ideally, in case 3, not "certified MQA" would be automatically detected by the NODE and provide volume control.
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Hi Daniel
As per MQA's requirements and specifications, the MQA External DAC switch already does that;
1) MQA DAC is on - You get MQA
2) MQA DAC is off - You are getting audio but it is not MQA
3) MQA DAC is off - You are getting audio but it is not MQAIn all cases, you should still receive Audio
Please remember - MQA is a universal industry format and requires specifications for implementation. Bluesound and BluOS strictly adhere to those specifications as set down by MQA.
Thank you for your patience and understanding.
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I realize I'm not getting my point through - or - it could of course be my misunderstanding.
It is about the volume control... In my world 2 and 3 are not the same.
In one case I get the MQA stream bypassed directly to the DAC with audio in HR quality but I then get no BluOS volume control.
In another case the NODE decoder provides 24/96 to DAC and I have BluOS volume control, but no audio!
I'm missing the case where MQA stream is bypassed directly to DAC, giving HR quality, but still with BluOS volume control. This should not violate MQA specs if the NODE knows that the chain is currently not MQA certified!
I have a way of tricking the NODE into volume control mode by switching between first and second case during playback!
I'm the one to thank you for your patience.
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