SMSL VMV A2 Review (Stereo Amplifier & DAC)

SMSL VMV A2 Review (Stereo Amplifier & DAC)

This is a review and detailed measurements of the SMSL VMV A2 stereo “desktop” DAC and amplifier.

The look and feel of the A2 is similar to the latest line from SMSL:

It looks nicer though in this “widescreen” presentation. The rotary encoder feels a bit looks physically but is very responsive.

As noted, there is an integrated DAC in the A2:

I like the diagonal binding posts which gave me more room than I typically find in these smaller desktop amplifiers.

As set of stick on feet were provided that I did not like that much but they also supplied tall spikes which you may have to use to provide ample room for the little fan underneath to suck air into the unit:

I could not feel much air moving though as the only exhaust are the two slots in the back. I rather have something moving air than nothing though. Then again, at close distance you can hear the fan running. Music though overwhelms it so probably not a big issue in practice. In use, the A2 got warm to touch but nothing that concerned me especially given the very solid chassis.

A remote control is provided which I did not use. Instead, I used the intuitive user interface to select inputs and such. A number of EQ profiles are provided which I did not try to understand or use. There is no documentation on what they do in the manual. Best to look up the same from ST Micro datasheet on which this amplifier is based on.

Edit: this amplifier topology uses a good baseline class D amplifier from ST Micro but then augments it with the AX5689 digital feedback control system from Axign. This serves to highly linearize the response of the amplifier as you see later.

SMSL VMV A2 Measurements
I started with analog input but ran into an issue I have seen with some ST Micro implementations that pull in the loop filter:

There seems to be low frequency energy or DC pumping into my analyzer causing SINAD to jump from 65 to 83 dB. No amount of messing with grounding and such helped in any way. What completely eliminated it was using Coax or USB Input:

Now we are talking! This is excellent performance for a desktop amp, putting the A2 in the likes of Hypex class D amplifiers:

There is some genius behind the design of this ST Micro chip amp. The A2 is the best execution of it and it shows.

Signal to noise ration is very good:

We are clearing the 16 bit audio hurdle at just 5 watts which is my target which sadly many amps fail to achieve.

The second puzzle was the frequency response. Here I am driving the amplifier using Coax at 192 kHz sampling so we should have flat response to half of that but we don’t:

Indeed, you can set the sample rate to anything you want, change to USB, etc. and you always get what seems to be 44.1 kHz sampling! SMSL advertises the “high-res” capability heavily in this amp but while the DAC is likely capable of delivering that, the amplifier happily shuts any extra spectrum above audible band.

The subwoofer output has gain control but not any other parameters:

Note also that the main speakers will always run full-range.

Crosstalk is insanely good:

Maybe the DAC is muting one channel and hence the excellent results. I did not try to investigate.

We have plenty of power into 4 ohm:

Not much headroom though as is typical of class D designs:

An aggressive protection circuit would shut the unit down when I tried to get max power at 1%. Fortunately the box automatically reboots and is back to business without any user intervention.

8 ohm load cuts the power in half:

As we have seen from other STM measurements, this is one linear amplifier with no care about the frequency or level:

SMSL VMV A2 Listening Tests
I test the A2 with my lab infinity Reference R253. The A2 had no problem pushing these speakers to insanely loud levels while volume level remained between 45 and 50 dB (all testing was using USB). The sound was absolutely clean, authoritative with zero issues to complain about. If the amp has a limit, it doesn’t show up in this type of testing.

SMSL pushes the boundaries of desktop amplifiers producing a powerful and very clean design if you use digital input. Analog input has some low frequency problem which has a tiny chance of being instrumentation issue. Hopefully they can comment. BTW, if you use a-weighting, the problem disappears since it filters that spectrum. And this is not an audible problem due to very low frequencies involved.

Use of a fan is a bit of bummer but I don’t think it is a practical concern.

Subjectively the A2 delivers with plenty of power to drive any small to medium system with plenty of headroom left. And oh, those of you who hate high-res, now have the perfect amplifier as it won’t try to reproduce ultrasonics anyway!  Fortunately feeding 24-bit data does work so don’t through out high-res content that quickly.

Overall, I am going to recommend the SMSL VMV A2 amplifier.

NOTE: this is a review of a new product. My recommendation is strictly based on its performance in the limited time I had with the unit. You are responsible to research issues of reliability, functionality, support, long term stability, etc. on your own. Please don’t be an early adopter if are risk averse in these regards.

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