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Audiolab M-DAC Flickering 16/24 bit and Idiots Guide to the M-DAC

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PinkFroyd

Member
I have just got a new M-DAC (original JW version). I was after a 2nd CDQ (for another room) but then found the MDAC can be bought new for less than a used CDQ; no brainer as I no longer use CD's other than to rip them losslessly to my NAS.

I am feeding the M-DAC from a Sonos ZP90 (cabled, not wifi), via toslink, from a lossless audio original, ripped using DP Poweramp so bit perfect in theory (on disk) and therefore 16 bit, no question.

I have jitter set to medium bandwidth as on auto I get tiny dropouts in sound. (The CDQ is set to auto although I recall having the same issue in the past and needing to set to medium, but oddly now seems OK.)

On the M-DAC while playing the 16 bit/24bit indicator will flicker, mostly showing 16bit, but flickering up to 24bit frequently. The EC3 decorrelator indicator also flickers. There is no obvious audio issue to my ears. (I don't know what the EC3 is set at and I can't check now as I was sent a used M-DAC by mistake and have sent it back to be replaced)

I do have a new optical lead on order just in case the old one has been snagged. And of course a new M-DAC coming, so will be interesting to see if that is the same.

Any ideas?

On a related topic, is there in the forum an "idiots" guide to all the settings on the M-DAC? The manual is a bit sparse - eg it says I can set D3E to unmodified, partial or full suppression, but no indication as to when or why I would choose these settings and what effect they may have. The same for the jitter - if it said hi medium and low jitter I could understand, but it says bandwidth. Now I think if I sub "Bandwidth" with "Jitter" I get what I need in my understanding. Set high for high jitter sources etc. Or set the lowest which works might be another way to say it. Back in the day I just put my disk in and played it, no options and have not really kept up with the detail and settings of the newer technology. All I want to do is set up once and enjoy the music, but I'd rather set to the optimum settings - as a lot of these settings are subtle and perhaps only needed on certain sources, it's not always easy to say "trust your ears".
 
Is it possible that the sonos is applying a digital volume control? If so that might make the bit depth become 24.
 
I'm not sure - I will look into that. But why would it flicker between the two.

On that general point though, would there be something fundamentally preferable (from a quality standpoint) to using a fixed output on the Sonos. I am using it variable, although I normally have it set to max and adjust at the DAC. Which in my logic is no different to fixed, but it depends how the Sonos deals with it I guess
 
It seems that Sonos does use 24 bit volume control, so this quite possibly is part of the conundrum. I will have a play between fixed and variable volume and see if it makes a difference. When I get my replacement that is ................... DPD arrived for the collection, waltzed to the neighours house - 21A not 21 and buggered off before I could run out and say it's number 21 you are after. Arghh !!
 
I am using the latest out of the box audiolab firmware.

Along with a sticky on the details of the various options, one with the summary of the pro's and con's of each of the Lakewest firmware versions would be great. I've searched the forums a lot and seem to glean that John things his A0.8 is the best/most stable, but it isn't that clear.

I'm not unhappy with the stock sound, so reluctant to fiddle - I also don't see a return to factory firmware version in case you wanted to do that - it seems to be a one-way street.

Plus, I would rather assume and fix external issues before looking at the box itself. It may not even be an issue per se.
 
PinkFroyd said:
I'm not sure - I will look into that. But why would it flicker between the two.

On that general point though, would there be something fundamentally preferable (from a quality standpoint) to using a fixed output on the Sonos. I am using it variable, although I normally have it set to max and adjust at the DAC. Which in my logic is no different to fixed, but it depends how the Sonos deals with it I guess
Click to expand...
I don't know, it's almost as though the VC is cutting in and out.
 
adamdea said:
I don't know, it's almost as though the VC is cutting in and out.
Click to expand...
Yes, it seems like that. It was set to max but not fixed. Replacement MDAC not arrived yet, so can’t check.

Btw, if you want a new MDAC they are now in short stock due to Chinese New Year slowing replacement stock.
 
If you can organise a bit perfect test, then that will tell you if the Sonos is delivering a bit perfect stream to your MDAC. Any form of digital volume control will 'confuse' the sample bit depth / sample rate display, as will any form of lossy compression. I'm listening to a 320k AAC stream from BBC Radio 3 at the moment and my MDAC is telling me it's 24bit/48K and it's clearly neither!
 
JemHayward said:
If you can organise a bit perfect test, then that will tell you if the Sonos is delivering a bit perfect stream to your MDAC. Any form of digital volume control will 'confuse' the sample bit depth / sample rate display, as will any form of lossy compression. I'm listening to a 320k AAC stream from BBC Radio 3 at the moment and my MDAC is telling me it's 24bit/48K and it's clearly neither!
Click to expand...
I think it might be 48 kHz
 
Then, I suspect you are not getting a bit perfect stream. I'm not familiar with Sonos, so can't advise further, but if it sounds good, I'd not worry too much. Few, if any, DACs enable this level of analysis / paranoia, so most people will be blissfully unaware that their bitstream is slightly compromised.
 
So, finally got the new mdac. This one shows 16bit with fixed volume and 24bit with variable volume from the sonos. As expected, so I think the other one was faulty. I’ve not changed anything else.

I learned some stuff in the process at least. Thanks for all the replies.

Not sure how to do a bit perfect test,as the link to the file isn’t working.

Which makes you realise accepting an open box unit is a risk, so glad I dug my heels in and returned it.
 
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