DSP upsample rate or not for Auralic vega

(Michael Mowery) #1

I have the first generation Vega by Auralic. The DAC upsamples PCM rate to 1.5MHz at 32bit. However, I am using AES/EBU balanced input from my Aries streamer to the Vega which has a maximum sampling rate of 24bit / 192 KHz.

My question is Do I use DSP to upsample everything to 192 KHz? Or is the Vega is already doing that. Do I just set the sample rate to “For Compatibility only”? Just trying to figure out the best setting.

(Scott G) #2

I think you need to find what sounds best to you. I have an MSB DAC and I’ve tried every combination of upsampling and always come to the conclusion my DAC does it best. I was struck by the improvement in sound quality after an MSB firmware update where they changed their internal processing algorithm. So how do you objectively determine what is best other than listen?

(Andrew Cox) #3

I use an original Vega in a second system at my partner’s house. I also like the AES input on the Vega and run an Allo DigiOne into it with a converter.

The Vega does internally upsample input (I forget what to), but if you feed it an externally upsampled signal it will bypass it’s own upsampling to the extent of that signal. Because the first upsampling in a chain has the most audible effect, this can mean there is an advantage to upsampling to 192 kHz in a general computer.

In my setup I upsample to 192 kHz in Roon (ROCK on a BRIX) and send it to the DigiOne and then the Vega. I think it sounds better, but wouldn’t trust that I can tell the difference in a blind test.

The good news is you can listen to various combinations and decide which sounds best to you.

(Michael Mowery) #4

Thank you Andy. I will let my Vega upsample the incoming signal and not let Roon upsample. I will try that out for awhile.

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(Michael Mowery) #5

I was confused with having the AES digital input and thought I should up sample first via Roon but now I will just let my Vega to it.

(Michael Mowery) #6

I am trying to understand what is going on when I use a connection on my DAC that limits the sample rate coming in. I guess i should not have Roon upsample to the AES connector 192k sample rate but wait and let my DAC upsample it afterwards to the maxim PCM sample rate which is much higher than 192k.

But I am still confused as what the difference is between disabling sample rate conversion controls in DSP vs just checking “for compatibility only”? I think I will just leave this control disabled.

(Andrew Cox) #7

Different protocols and hardware used for different connections have different bandwidth limitations. Sometimes the limits are self-imposed by DAC designers who don’t have confidence in the tolerances of a connection above a certain bandwidth.

This post by Jussi Lasko is the best description I have read of what happens in a typical delta-sigma chip DAC, such as the Vega.

There can be advantages to bypassing upsampling within a DAC by doing it in a more powerful general computer that is isolated from the DAC by Ethernet. That is part of the reason Roon offers the option. See this KB page for more details about Sound Quality and this one for more about Sample Rate Conversion.

If you disable DSP Sample Rate Conversion then Roon will never up/downsample. If you enable “For Compatability Only” then Roon will only up/downsample to enable an otherwise incompatible file (sampling rate lower or higher than your DAC accepts) to be played by your DAC. Roon will know what your DAC can accept over various inputs if the DAC is Roon Tested (which the Vega is).

So if you prefer to upsample in the Vega, which is a perfectly valid choice that Auralic might reccomend, then you can still use Roon up/downsampling for compatability purposes only. The Signal Chain will tell you if this is happening. In the case of the Vega it would happen if you played a DSD file into the AES input for example. Roon would convert the file to PCM 192 kHz so it was compatible with the selected DAC input. If you connected the Aries to the Vega by the USB input, then Roon would pass through or downsample the file to the DSD capability of the Vega USB input.

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(Mikael Ollars) #8

I have a slightly different view on this Andrew, wrong or not…
If you disable all DSP, Roon will still apply compatibility resampling based on the endpoints capabilites, as set in Settings-Audio for each endpoint.

Which makes the setting in DSP, “For compatibility only” a bit dubious to what it actually does, or not.

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(Andrew Cox) #9

Thanks Mikael, I’ll do some experimentation and see if I can replicate. I was describing my understanding of what was intended. Obviously what is actually happening is more relevant.

(Scott G) #10

Well, wouldn’t you hope it would be designed to do this? Only the craziest purist would rather have no sound (Roon and the DAC can’t communicate) than one that has had the frequency adjusted from 88kHz to 96kHz. :wink:

(Mikael Ollars) #11

Absolutely, it works just fine! And i’d rather not have it any other way! :slight_smile:

My reflection was rather, “when enabling Sample rate conversion in DSP, does the full DSP up-/resample module come into play?”
It does provide the option to select filters and some Sigma-Delta conversion settings, which are not available elsewhere.

(Scott G) #12

I get it now. Yeah, that’s an important distinction I hadn’t thought of.

(Daniel Beyer) #13

(Note, I could be wrong as I don’t know for sure, I just think it works this way. :slight_smile:)

If you are talking about this for example:

I would say yes, the filter option applies at all times, because, the option is still available when the Sample Rate Conversion is turned off. So, I would expect it to be applicable to Conversion based on Device Settings as well. It would be weird for it not to, imho.

Conversion based on Device Settings take precedence over DSP Conversion settings, and, happen whether you have DSP turned off or on. If you set your DAC which can do 192k, to a Max of 48k in the Device Settings, if you then go to the DSP section you will find that it is limited to 48k (if you choose custom) as a Max conversion. Even with DSP Conversion turned off, any 192k original source would be downsampled to 48k (Based on the Device Setting, and, again I assume, have the applicable selected filter applied.

But, if we want to know for sure we can always, ask, @dylan. :smiley:

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