[Rob Watts]

Unfortunately not - none of my DACs send or receive volume control data via USB.

 

[Tims Fong]

Unfortunately not - none of my DACs send or receive volume control data via USB.

I see, thank you for your reply.

 

[Alifatemi]

Hello Rob. I have Qutest DAC and like to know more about M scaler; I have never liked upsampling either through hardware DAC or software like Roon and always ending got back to the original. Does M Scaler add something to the sound like say, photoshop that when upsample a low resolution file, it double or triple neighbor pixels to increase the resolution which is nonsense or what? Regads

 

[Rob Watts]

It depends upon what you define as the "original". By original you are thinking about the digital data; when I think about the original I am thinking about the analogue signal in the ADC that existed before the signal was sampled; and these are very different things. The original data is simply a snapshot of the analogue signal, and we need to recover the original continuous (that is not sampled) analogue signal. Fortunately, we can recover a bandwidth limited signal absolutely perfectly if we use a sinc function filter; but a sinc function filter requires an infinite amount of processing.

The M scaler WTA algorithm provides enough processing power with it's million taps so that it is identical to the ideal sinc function with better than 16 bit accuracy; so we recover the original analogue signal to better than 16 bits under all conditions.

Why is this needed? It's because the timing of transients is a vital requirement for psychoacoustics; we get the perception of pitch, timbre, soundstage and the perception of timing from transients; and regular filters have transient timing errors (the reconstructed transient is either a little too early or a little too late); but with the M scaler we can reconstruct the transients to a guaranteed better than 16 bit accuracy. This is the reason why the M scaler sounds so fundamentally different.

 

[Alifatemi]

It depends upon what you define as the "original". By original you are thinking about the digital data; when I think about the original I am thinking about the analogue signal in the ADC that existed before the signal was sampled; and these are very different things. The original data is simply a snapshot of the analogue signal, and we need to recover the original continuous (that is not sampled) analogue signal. Fortunately, we can recover a bandwidth limited signal absolutely perfectly if we use a sinc function filter; but a sinc function filter requires an infinite amount of processing.

The M scaler WTA algorithm provides enough processing power with it's million taps so that it is identical to the ideal sinc function with better than 16 bit accuracy; so we recover the original analogue signal to better than 16 bits under all conditions.

Why is this needed? It's because the timing of transients is a vital requirement for psychoacoustics; we get the perception of pitch, timbre, soundstage and the perception of timing from transients; and regular filters have transient timing errors (the reconstructed transient is either a little too early or a little too late); but with the M scaler we can reconstruct the transients to a guaranteed better than 16 bit accuracy. This is the reason why the M scaler sounds so fundamentally different.

Thanks Rob. By original I mean original digital redbook or high res files I have without upsampling. I like their sound better compare to when I upsample them via Roon lab. Also I have done lots of comparison beetween redbook/ highres files and their counterpart MQA on Tidal. I have a very high resolution and trsnsparent system comprising wilson sasha ll and Audio research amps supplied by my Chord Qutest. As You said, with Qutest its very obvius that MQA sound qualit is inferior even to redbook files( 16/44.1) Mqa got far less dynamic, less vibrant and silky and silly softer sound which mitgh misslead many listeners but shows its real weakness in long term. Grant Green’s Street of Dreams is one of them. Tidal cd’s quality is even better than Tidal MQA. I dont have MQA DAC to reach my final verdict but at least with Qutest I can say I dont like MQA. Of course I kerp my mind open for futhure listening and comparison and post here. Cheers...

 

[AndrewOld]

Thanks Rob. By original I mean original digital redbook or high res files I have without upsampling. I like their sound better compare to when I upsample them via Roon lab. Also I have done lots of comparison beetween redbook/ highres files and their counterpart MQA on Tidal. I have a very high resolution and trsnsparent system comprising wilson sasha ll and Audio research amps supplied by my Chord Qutest. As You said, with Qutest its very obvius that MQA sound qualit is inferior even to redbook files( 16/44.1) Mqa got far less dynamic, less vibrant and silky and silly softer sound which mitgh misslead many listeners but shows its real weakness in long term. Grant Green’s Street of Dreams is one of them. Tidal cd’s quality is even better than Tidal MQA. I dont have MQA DAC to reach my final verdict but at least with Qutest I can say I dont like MQA. Of course I kerp my mind open for futhure listening and comparison and post here. Cheers...

Err.. Grant Greens Street of Dreams was recorded in 1964 onto analogue tape, way before digital recording. No way it is an original digital red book recording. Not that i think MQA makes any sense, but with a recording like that you have no idea what you are listening to, apart from degraded 50 year old analogue tape, or copies thereof, so using it as a basis for comparison is far from ideal.

https://en.m.wikipedia.org/wiki/Street_of_Dreams_(Grant_Green_album)

 

[musickid]

Is the recovered analogue signal post 1M tap processing fully identical to the analogue signal in the ADC that existed before the signal was sampled? Or is there a small margin of error? I think i asked this way back just recapping here.

 

[Rob Watts]

Is the recovered analogue signal post 1M tap processing fully identical to the analogue signal in the ADC that existed before the signal was sampled? Or is there a small margin of error? I think i asked this way back just recapping here.

In principle yes; in practice it depends upon the ADC itself, as ADCs have aliasing problems, so the decimation is not done correctly. And once an aliasing error is created, it's impossible to repair it. But assuming there is no aliasing errors, and the ADC itself creates no distortion or noise floor modulation, then it would be fully identical to the analogue signal to within 16 bit accuracy. Unfortunately, modern ADCs are not capable of this, but I fully expect Davina to be able to easily do this.

 

[Paul Bjernklo]

In principle yes; in practice it depends upon the ADC itself, as ADCs have aliasing problems, so the decimation is not done correctly. And once an aliasing error is created, it's impossible to repair it. But assuming there is no aliasing errors, and the ADC itself creates no distortion or noise floor modulation, then it would be fully identical to the analogue signal to within 16 bit accuracy. Unfortunately, modern ADCs are not capable of this, but I fully expect Davina to be able to easily do this.

Hi, I am a bit confused if the 16 bits referred to here is in any way related to the number of bits that the file was recorded at, ie does it mean that finally 16 bit recorded files come out with 16 bit accuracy, and not the much fewer bits accuracy that I assume applies for other “ordinary” DACs? If so does the same apply for any higher bit recordings like 24 bit and they also comes out with 16 bits accuracy with the M scaler (and if so what’s the point with hi res apart from higher sampling rate for any DAC?) or am I comparing Apples with Oranges?

Edit: If bits refer to transient timing and not signal amplitude as per a following post, what do the 16 bits refer to and what is a normal benchmark /average value to compare to? Thank you....

 

[castleofargh]

Hello Rob. I have Qutest DAC and like to know more about M scaler; I have never liked upsampling either through hardware DAC or software like Roon and always ending got back to the original. Does M Scaler add something to the sound like say, photoshop that when upsample a low resolution file, it double or triple neighbor pixels to increase the resolution which is nonsense or what? Regads

just to point out that picture interpolation is a very bad analogy with audio upsampling/oversampling. when creating more pixels out of a pic, there is no actual information about what those extra pixels should be. the ultimate result would be to visually mask the lines formed by the original pixels. so 1) it's about making something up. and 2) a fine subjective result is the ideal target.

with music, the recorded signal is well defined up to about half the sample rate. we know that it's all sines and sums of sines so we don't have to guess where an in-between point is going to be. we know!
adding extra samples clearly doesn't add information, it just presents the information we already have in a form that might be more convenient for some specific operations.

 

[Samuel Snoopy]

In principle yes; in practice it depends upon the ADC itself, as ADCs have aliasing problems, so the decimation is not done correctly. And once an aliasing error is created, it's impossible to repair it. But assuming there is no aliasing errors, and the ADC itself creates no distortion or noise floor modulation, then it would be fully identical to the analogue signal to within 16 bit accuracy. Unfortunately, modern ADCs are not capable of this, but I fully expect Davina to be able to easily do this.

Hi Rob, Is the 16bits accuracy talking about transient timing but not signal amplitude?

 

[Alifatemi]

Err.. Grant Greens Street of Dreams was recorded in 1964 onto analogue tape, way before digital recording. No way it is an original digital red book recording. Not that i think MQA makes any sense, but with a recording like that you have no idea what you are listening to, apart from degraded 50 year old analogue tape, or copies thereof, so using it as a basis for comparison is far from ideal.

https://en.m.wikipedia.org/wiki/Street_of_Dreams_(Grant_Green_album)

Thanks Andrew for comment but; we got an analogue tape from which, we have 3 copies of different file format digitally sampled: one in 16/44.1, one in 24/192 and another in MQA. Whats wrong comparing them together? I didn say my files come from original digitally recorded master tape. Besides many 50s or 60s records are so great I cant find that qualty in todays recording, not even close. We just comparing 3 file format hopfully have come from one analogue master tape. Cant be more fair than this.

 

[maxh22]

I’ve noticed that with all of Rob’s dacs ,old reel to reel recordings and even some recordings that were recorded to cassette tape sound so real and lifelike. It really brings out the best of them I think.

With some ESS dacs they can sound bland and unmusical, AKM chipsets sound much more musical to me but lack a lot of the realistic properties I hear in Robs dacs including the Mojo.

Looking forward to Rob’s eventual Davina recodings

 

[AndrewOld]

Thanks Andrew for comment but; we got an analogue tape from which, we have 3 copies of different file format digitally sampled: one in 16/44.1, one in 24/192 and another in MQA. Whats wrong comparing them together? I didn say my files come from original digitally recorded master tape. Besides many 50s or 60s records are so great I cant find that qualty in todays recording, not even close. We just comparing 3 file format hopfully have come from one analogue master tape. Cant be more fair than this.

But there is no way of knowing that they came from the same master tape. And even if they did, you have no way of knowing that the mastering was the same in terms of eq, level, and compression etc. Different versions get released by different mastering houses at different times quite possibly from copy masters using different mastering. The only valid comparison to do is to take a known 24/192 master (say), compare it to itself downsampled to 16/44.1 (say) which is easy because you can use sox, or J River or any resampler you like, and also convert it to MQA and back which alas you can’t do because of the secret and proprietary nature of MQA.

 

[514077]

Thanks Andrew for comment but; we got an analogue tape from which, we have 3 copies of different file format digitally sampled: one in 16/44.1, one in 24/192 and another in MQA. Whats wrong comparing them together? I didn say my files come from original digitally recorded master tape. Besides many 50s or 60s records are so great I cant find that qualty in todays recording, not even close. We just comparing 3 file format hopfully have come from one analogue master tape. Cant be more fair than this.

How did you perceive the diference between your copy of 24/192 vs CD quality? I don't bother or worry about MQA, as Chord doesn't use it, and I don't have any other DACS. Oh yes; welcome to Head-fi.