SMSL VMV A2 Review (Stereo Amplifier & DAC)

[respice finem]

Thanks for the review. I don't quite understand one sentence: "The rotary encoder feels a bit looks physically but is very responsive. " Possibly the right word is "loose"?

 

[gvl]

Thanks for the review. I don't quite understand one sentence: "The rotary encoder feels a bit looks physically but is very responsive. " Possibly the right word is "loose"?

"Loose" is my guess. It is the same encoder SMSL uses on other products, and it is kinda wobbly.

 

[dominikz]

That said, occasionally I can test with a real speaker if there is interest for some reason.

Thanks! At least to me that would be interesting - as it would show when an amplifier has high output impedance.

 

[SylphAudio]

Hmmm. The SMSL web site has exactly the same digram depicting the feedback loop as we saw for the SA400. That is the AX5689 PWM controller. Indeed it is hard to imagine that this amp is anything but an SA400 power amp stage with a DAC. Amir measured exactly the same power ouput curves for both, but the SINAD is better here. Again, the ST part is the output driver only, and not the full class D amp. All digital processing and PWM control, just like the SA400, is done in the AX5689.

Looks like a game changer indeed.
https://audioxpress.com/files/attachment/2659

 

[abdo123]

The amp technology has good potential but the cons of using a fan, frequency response limitation and bad analog input are very disappointing.

The ‘bad analog input’ is utterly inaudible, the rise in noise is still below the human hearing thresshold.

 

[voodooless]

Looks like a game changer indeed.
https://audioxpress.com/files/attachment/2659

Imagine an 8 channel XMOS coupled to an AX5689 with 8 output stages. Would be the ideal combination for a software DSP active system! Not sure why they choose 44.1 kHz internal sampling though? 48 kHz would have given just that bit extra bit of headroom.

It's too bad the review doesn't mention the use of this technology. It's a science forum, we should be geeking out over this

 

[anphex]

Even if a audio device not perform very good or even below average, once a manufacturer sends their device to Amir for testing they already gain something from me: trust and respect. I'd take any manufacturer that provides hard cold third party data before the ones that sprinkle fairy dust on their spec sheet it shrouds itself in secrecy.

Wasn't it that the data sheets sometimes aren't even based on measurements and just a copy and paste of the main DAC or OpAmp?

Anyway SMSL looks good. Although the low frequency noise would bother me personally.

 

[GWolfman]

An aggressive protection circuit would shut the unit down when I tried to get max power at 1%.

I'm afraid I don't understand. Or was this supposed to be 100%?

 

[respice finem]

@ 1% THD I suppose

 

[SMSL-Mandy]

VMV A2 The fan will turn on when the temperature is higher than 65 degrees.
The info of Digital PFFB;
The info of A2;

 

[trashken]

VMV A2 The fan will turn on when the temperature is higher than 65 degrees.
The info of Digital PFFB;
The info of A2;

Hi Mandy, can you comment on the high SINAD observed by Amir when using Analog In?

 

[amirm]

I'm afraid I don't understand. Or was this supposed to be 100%?

No, that was power at THD of 1%. The analyzer needs to adjust the power up and down until it hits this target. With this amp's protection circuit, as soon as you get near clipping, it shuts down so there was no practical way to measure power at 1% THD.

 

[amirm]

It's too bad the review doesn't mention the use of this technology. It's a science forum, we should be geeking out over this

I updated the review to indicate this.

 

[SylphAudio]

Like what Francis has said, ST Micro chip used in this amp is not a standalone class-d chip, it is just a power stage, the STM chip contains multiple half bridge mosfet circuit with protection circuitry built-in and mosfet drivers that accept PWM inputs.

The brain is in AX5689 class-d modulator / PWM controller.

By making the input and the processing digital, they can get away with Bruno's PFFB patents.

I'm interested in partnering AX5689 with GAN mosfets power stage. (easier with irs20957 mosfet driver like in eval audamp24) I can't find AX5689 in any electronics distributors though.

 

[xema]

It's an all digital amp (not a typical analoge class D), the analoge inputs lead to a ADC inside, very interesting.

 

[kipman725]

Imagine an 8 channel XMOS coupled to an AX5689 with 8 output stages. Would be the ideal combination for a software DSP active system! Not sure why they choose 44.1 kHz internal sampling though? 48 kHz would have given just that bit extra bit of headroom.

It's too bad the review doesn't mention the use of this technology. It's a science forum, we should be geeking out over this

I tried to get the datasheet for AX5689 even using a non personal, big engineering email address and didn't even get a reply which is a bit of a turn off.

 

[Mulder]

You say that so generically. You mean test with any random CD player? Or some with certain characteristic? I can test for level, jitter or both but need to know the nature of the problem.

This is because some DACs that you have tested have been found to be unreliable when it comes to CD players. The Topping D30Pro, which I bought after reading your test, turned out to be unable to handle the signal from my CD player. It is as if the DAC loses the signal from time to time, the sound chops or hangs up at frequent intervals. It is as if the DAC cannot lock the signal. However, this does not apply to all CD players, but it applies to enough CD players that one must advise against buying the D30Pro if the intention is to use it with a CD player. I can not really see how this can be tested because only some CD players have the problem. But according to what was said by the designer (I guess it is) it is related to the level of jitter from the CD player.

 

[noel_fs]

What alternatives would you suggest with this kind of performance and a built in DAC?

I dont see the built in dac as a positive. Alternatives would be any ncore + external dac (for 600 you can get a setup thats superior to this, especially considering price difference). For a little more than 1000 there is eigentakt prebuilt stereo on audiophonics at 1400 which would be absolute endgame with much more power than this for little more money, relatively speaking. Another option would be going for vintages, but thats a headache to do the research imo.

If this thing was priced in the 500 range then i would be quiet but for 1000 they are just being greedy and we should not let them price things as they please, its part of the problem why so many things are overpriced in the "audiophile world"

 

[noel_fs]

This is because some DACs that you have tested have been found to be unreliable when it comes to CD players. The Topping D30Pro, which I bought after reading your test, turned out to be unable to handle the signal from my CD player. It is as if the DAC loses the signal from time to time, the sound chops or hangs up at frequent intervals. It is as if the DAC cannot lock the signal. However, this does not apply to all CD players, but it applies to enough CD players that one must advise against buying the D30Pro if the intention is to use it with a CD player. I can not really see how this can be tested because only some CD players have the problem. But according to what was said by the designer (I guess it is) it is related to the level of jitter from the CD player.

who has the intention to use an external dac with a CD player in 2021? Thats no reason to discredit a product like D30Pro, especially considering it happens with some player which says to me its more of a compatibility issue of the cdplayers likely the cheapest possible implementation to be able to add another output to the specifications with no intention to actually use it because, who would? You either get a CDPlayer for its internal dac or you play the files with a computer.

 

[Mulder]

who has the intention to use an external dac with a CD player in 2021? Thats no reason to discredit a product like D30Pro, especially considering it happens with some player which says to me its more of a compatibility issue of the cdplayers likely the cheapest possible implementation to be able to add another output to the specifications with no intention to actually use it because, who would? You either get a CDPlayer for its internal dac or you play the files with a computer.

Who are you to tell me what to do? Thera are lot of reasons why one could prefer an outboard DAC. And besides, ever heard about CD-transports without an inbuilt DAC? Now, this is of topic, but a question was raised in the tread.