Only Partial Decoding of MQA with the Direct Stream DAC/ Bridge II system


#1

Although I generally like and appreciate the performance of my recently acquired DirectStream DAC and BridgeII along with DirectStream Memory Player, I was greatly disappointed to find that their much-heralded addition of MQA capablility is only partial, that is PS Audio currently provides only the first “unfolding” stage of MQA translation but not the second decoding of MQA encoding. (For further elucidation of this see articles in recent issues of The Absolute Sound.) I must admit PSAudio’s advertising does not make this clear and I feel somewhat misled. In fact even the tech with whom I spoke about this issue on the PSAudo 800 telephone line did not know PS Audio’s machines were lacking in this respect. Had I known I might very well have bought another brand of player and DAC, perhaps Brooklyn.

Does the company have any plans to make this right? Certainly more forthcoming advertising is in order and how about a software update (one of the chief reasons I bought the brand in the first place) to add the second step of MQA decoding?


MQA Controversy
#2

Welcome, brucewar!

There are many threads here discussing MQA, and also PS Audio’s current implementation as well as future plans. I suggest spending thirty minutes or so digging around and reading.


#3

So, apart from the MQA aspect you’re happy with the new PS Audio gear…that’s great! and welcome to the PS Community family, all new members welcome!

For me MQA hasn’t been something that has attracted my attention, and I think I’ll keep it that way.


#4

Playing the devil’s advocate (I don’t speak for PS Audio about MQA nor the Bridge): the one time I talked to Bob Stuart about this he didn’t seem too concerned in the DS’s case (perhaps I missed some behind the scenes stuff.) I’m pretty sure the DS does better upsampling from, say, 96 to 384kHz than doing 1/2 of it in the Bridge via MQA (96 to 192k) and then another half in the DS FPGA (from 192k to 384k.) Bob/MQA know what kind of filters we use in the DS and didn’t seem to have any qualms at all about them. There’s plenty of frequency space for doing the apodizing filter in the first level of unfolding and I suspect that that get’s much of the MQA “goodness” right there. There are certainly DAC out there that benefit from MQA unfolding to 176.4k or 192k but it actually may hurt the MQA/FPGA implementation in the DS.


#5

Ted, thank you for the response but it is not quite clear what yu are saying. If I get it correctly you are saying that the DirectStreamDAC/BridgeII does not perform the full “decoding” of MQA but is good enough it doesn’t need to do so. Could you either confirm that or if I misinterpreted something could you please say it again in English for the layman without the abbreviations (FPGA?) Thanks


#6

The way the bridge and the rest of the DS cooperate allows each to do what it does best. Putting more computation in the bridge (full decoding) means that it can’t use nearly as good of upsampling filters. Putting more filtering in the DS allows much better upsampling filter implementations. There is the trade off that full decoding isn’t only upsampling, there’s a little more information in the higher frequencies, but that’s in the noise (perhaps literally with MQA) compared to the quality of upsampling available in the DS.


#7

@brucewar You are mistaken. You can get a full unfold of MQA with a DS DAC / Bridge II combination. The processing in handled by the BridgeII.

Here is a recent screenshot of my DSD/BridgeII:

P2120222.JPG

MQA. “Blue”. Studio Sign Off Complete unfold.

You can also get the complete unfold when streaming Tidal, but you must use the mConnect Control App.


#8

Oops, I’d forgotten that the latest bridge does more work so I guess you get what MQA wants you to get (whether or not it’s the best possible sound.)


#9

IIRC the bridge update that was released alongside (within a few days) of Redcloud allows for full unfolding. So that means it’s been available for about 3-4 months now. This is also when PS Audio started advertising that it was capable of full MQA unfolding. There’s nothing shady about the advertisements or articles you’ve seen or read, but I assume the one you read that told you it wasn’t able to do full unfolding was old before the big update last year.


#10

Brucewar, if you’re stilling having a hard time understanding what Ted is referencing, I’ll try and put it in simpler terms. What Ted is saying is that the upsampling Ted has designed and implemented inside the Direcstream will more than likely yield better sound quality if you were to feed it the first unfolded audio at 24/96 versus what can be extracted by a second unfolding up to the full 24/192. His filtering techniques are of extremely high quality.

I don’t own a Bridge II, but is it possible to tell it to only do the first unfold? That way you could compare sound quality of Ted’s filtering versus the second unfold.


#11

Actually, Bridge II via Mconnect Control App has been capable of FULLY unfolding MQA files since Huron and Bridge II firmware 3.3.3.

Rodrigaj is correct in that you must use the ConversDigital Mconnect Control App to get the Bridge to fully unfold the MQA file. In other words, you are getting the best of the best that MQA has to offer if delivered by this method.

If you use anything else, such as the Tidal software on your desktop or laptop computer, or Room, or any other software other than Mconnect to deliver your MQA streams or music files, then you will NOT get a fully unfolded MQA file - only a partially unfolded. BubbleUP is not capable of delivering fully unfolded files either.

Bottom line: You MUST use Mconnect Control app to get fully unfolded MQA files. But it is certainly possible on the DirectStream DAC with Bridge II.

What Ted has offered up is an entirely different discussion. I am not in position to say that partially unfolded, but better upsampled (By the DirectStream) MQA files sent to the DAC sound better than fully unfolded MQA with inferior upsampling. Again, that is an entirely different topic and one that is part and parcel to the DirectStream DAC having the capability to fully unfold MQA files via the Bridge II. It absolutely can!

[EDIT]: See my follow up reply below. Seems you can now stream via Roon and get full unfolding. And if you don’t stream, but have locally stored MQA, other control apps work in addition to Control app. This is good news!


#12

I don’t know. I was listening to an MQA track today using Tidal via Roon. The DirectStream display showed this:

IMG_1471.JPG

And Roon showed this:

Screen-Shot-2018-02-15-at-Feb-15-12.31.45-AM.jpeg

It seems that you can get a full unfold using Roon and the Bridge II.


#13

Jeff of Arabica

What I wrote above was that you must use mConnect to get the full unfold when streaming Tidal.

The picture I posted was using Lumin App as a control on an iPad, showing that the BridgeII was doing the unfolding on a NAS stored MQA file.

Sorry, I should have mentioned that.


#14
rodrigaj said

Jeff of Arabica

What I wrote above was that you must use mConnect to get the full unfold when streaming Tidal.

The picture I posted was using Lumin App as a control on an iPad, showing that the BridgeII was doing the unfolding on a NAS stored MQA file.

Sorry, I should have mentioned that.

Thanks for clarifying ridrigaj. I don't listen to digital via a NAS and assumed Mconnect needed to be involved in that, as well as streaming. This is good to know and useful for others who have locally stored MQA files.

Speed Racer, that is very interesting as this was not the case last year. I am curious as to what changed to allow Roon to fully unfold? Thanks for sharing that. I am actually excited to see some progress in this arena as I am not a fan of the Control app, as you all know.


#15

If anyone is interested in experimenting with MQA files that are downloaded (i.e., not streamed via Tidal) here is a very handy website.

This website also has all HiRes options as well. All for free.

Warning: They do throttle download speeds (at least they did for me), so expect long download times.

http://www.2l.no/hires/


#16

Roon, as of 2-15-18, is not doing anything to the Tidal MQA stream but passing it through unmolested to the Bridge II which now does full unfold. In Roon, all DSP processing and volume leveling must be disabled for this to work.

At some point in the future, Roon will perform the first unfold - hopefully before any, or in coordination with, DSP so that it can still be applied.

The difference for me between full MQA unfold and using convolution filters in Roon is no contest. I’ll take the convolution filters every time. I do enjoy MQA via headphones where I don’t use DSP but do miss out on crossfeed, which I prefer.

Fun times!


#17

A fully updated Bridge II can perform the so-called second MQA unfold up to 192k. The Bridge II tops out at 192k for PCM generally, so the rare MQA files which would unfold to 352.8k or 384k in a DAC with a hardware MQA decoder (e.g., the Mytek Brooklyn) are processed in the Bridge II at 176.4k and 192k respectively.


#18

The PS Audio DirectStream DAC with Redcloud and the Bridge II newest firmware sounds much better with MQA than the Mytek Brooklyn DAC which I had (I compared before I sold it).

The Mytek Brooklyn is a nice DAC for the money (I also had a PSU), but the sound on my system with all files IMO is no where in the same league as the DirectStream DAC (which is what you would expect for the price difference, but not always true unfortunately).


#19

This is why the Bridge III card, or whatever it ends up being called, needs to support DSD128 and PCM up to 24/384 AND needs to be a Roon endpoint.

@adminpaul I would be very happy to beta test the new Bridge card.


#20

Many of us would call the difference between 192 and 384 entirely theoretical, and since there is little or no such material anyway, the DSD doesn’t really need to support compression that has become fashionable since it was introduced. At some point, you need new hardware to process higher multiples of datarate.