Review and Measurements of SMSL VMV D1 DAC

[gvl]

It does when you measure it like that but RBCD files won't have those higher frequency.

The file won't, but the DAC will add its own (Amir posted this earlier):

Or at least this is how I interpreted it. Same noise is present on all sampling rates, albeit less pronounced on lower.

 

[amirm]

It does when you measure it like that but RBCD files won't have those higher frequency.

Not correct. The noise is not from the source or it would not show up in my 1 Khz test tones.

 

[helloworld]

Interesting. I found it suspicious SMSL folks were resistant to turn the HF filtering off here, sounds like it is a known issue to them.

Based on my communication with SMSL people past three days, they don’t know it. At first their react was kind of slow because their engineers are not good at English, Mandy has to translate every technical thing to the engineer and then the engineers do the test or give an explanation. Sometimes there are misunderstandings because Mandy is not an engineer and get confused with some special words we were talking here. They are taking it very seriously actually and yesterday their engineers had been holding a meeting for several hours to discuss these issues found here.They were a little bit quiet yesterday because they use a different analyzer Prism Sound dScope Series III and were trying to get one Apx555 to repeat all the tests in this review. They will respond as soon as possible when they finish all of the tests. @amirm actually they were thinking of directly contacting you to make sure their tests were identical to yours, but you know, language.....So discussion may go a little bit slow here but I am sure smsl will keep everyone updated.

 

[amirm]

They will respond as soon as possible when they finish all of the tests. @amirm actually they were thinking of directly contacting you to make sure their tests were identical to yours, but you know, language.....

Thank you for the help and background story. I have sent them email just in case they are more comfortable resolving things that way. I am here for any help they require. If I were not travelling, I would have contacted them when they first came to the forum.

 

[yummy]

the rca side surely is flawed, at least with this unit, don't know if this's a general problem for all units

 

[Krunok]

Not correct. The noise is not from the source or it would not show up in my 1 Khz test tones.

I know it's not from the source as it showed when no signal is present but doesn't DAC apply a filter after Nyquist freqeuncy? In 44.1 kHz case that would be after 22kHz or so..

 

[bennetng]

The Katana with ES9038Q2M also shows an ultrasonic spike at 88kHz and that's why I asked @amirm to do a filter test. But now I lost interest about this issue and become more interested in the D1's "tube sound" DSP profiles. Some believe that ESS's THD compensation is the culprit of "ESS hump" and I would like to see how D1's different DSP profiles affect the hump.

 

[amirm]

I am going out today. I will try to remember to run this when I get back later tonight.

 

[Krunok]

@amirm, how did you get those DACs to output over 100kHz? Don't they have out of band filters to prevent such HF garbage to come out?

I would expect them to apply filter to cut everthing above Nyquist frequency. Isn't that so?

 

[Krunok]

I am going out today.

That sounds like you've been grounded till yesterday!

 

[amirm]

@amirm, how did you get those DACs to output over 100kHz? Don't they have out of band filters to prevent such HF garbage to come out?

The filters are for the DAC, not the analog output stage. The analog stage is wideband to support the highest sample rate. Since the SMSL VMV D1 goes up to 768 kHz sampling, its output stage must be flat to at least 384 kHz. That wide bandwidth then allows noise to bleed into it.

 

[amirm]

That sounds like you've been grounded till yesterday!

Yes, I was chained to my analyzer running tests for you all.

Going to shop for a new computer monitor. Long drive to Fry's as none of the other places have much to look at.....

 

[Krunok]

Yes, I was chained to my analyzer running tests for you all.

While most of us cannot buy you a beer or a dinner we still very much appreciate your effort.

 

[JJB70]

Look on the bright side, it may have measurement issues but at least it won't try to electrocute you because they forgot about earthing the case........

 

[Krunok]

The filters are for the DAC, not the analog output stage. The analog stage is wideband to support the highest sample rate. Since the SMSL VMV D1 goes up to 768 kHz sampling, its output stage must be flat to at least 384 kHz. That wide bandwidth then allows noise to bleed into it.

I don't get it. Don't they have filter in the analog stage, after the U/I converter?

Are you saying that filter has been built into the DAC chip and there's no filtering after the U/I converter?

 

[bennetng]

I don't get it. Don't they have filter in the analog stage, after the U/I converter?

https://www.computeraudiophile.com/...age-losing-focus/?tab=comments#comment-750197

 

[amirm]

I don't get it. Don't they have filter in the analog stage, after the U/I converter?

All the filtering is in the DAC chip itself, unless it specifies otherwise. The buffer stage can have filtering but it is not because the DAC needs it.

There are some DACs where you can disable the filtering and do that externally ()Berkeley Alpha DAC comes to mind) but that is not how they are typically used.

 

[Krunok]

https://www.computeraudiophile.com/...age-losing-focus/?tab=comments#comment-750197

When they say "DAC" do they mean the DAC chip or the DAC device (chip+analog output stage)?

 

[Krunok]

All the filtering is in the DAC chip itself, unless it specifies otherwise. The buffer stage can have filtering but it is not because the DAC needs it.

Huh, I see. Of course DAC doesn't need it, but the U/I converter needs it. That is the reason the analog stage is picking all that noise as it must cover high frequency band and there's no filter in the buffer stage to cut it at Nyquist freq. IMO that is not how it should be done. If there would be a filter in the buffer stage that would cut after the Nyquist things would look much better with your measurements.

But, of course, doing everything in one chip and simplifying the analog stage cuts the cost.

Btw, why should we care about out of the band garbage when speakers/headphones anyhow can't reproduce them? Can they disturb the amps?

 

[Krunok]

https://www.computeraudiophile.com/...age-losing-focus/?tab=comments#comment-750197

"Higher those are moved, more the DAC's analog filter manages to cut those out and less ultrasonics there are going out to the amplifiers and loudspeakers. "

Is this what we're affraid of? That ultrasonic garbage may cause instability within the amp or burn the coils in the tweeters?