SMSL VMV A1 Pro Stereo/Mono Amplifier Review

[Audionaut]

Otherwise, even IC amplifiers outperform the A1Pro

That is the point.
There are not many amplifiers that deliver better and more power than well-made TPA3255 amplifiers with a 48V 10A power supply.
If there are, they are much more expensive.

 

[amirm]

@amirm Thanks Amir for again another nice review. Question: Would it be a good idea to add to the % of max power to the 40 Hz power graph? That's probably a more interesting metric since all these amplifiers listed have different max power ratings.

I would have to compute it manually but sure.

 

[DSJR]

@Daniboum

I don't need to reread what was tested and measured by Amirm (and others): EVERYTHING written and observed is accurate

However, there was a certain Ken Ishiwata whose life was rather 'prolific', improving, for example, CD players of his time with other components selected by himself, including OPAMPS and capacitors ('KI signature' devices).

Do you think he possessed less skill than Amirm ?

Perhaps he was measuring 'certain things' that we don't measure because the devices he modified clearly had better SQ.

Almost everything I ever heard with a 'KI Signature' label on the front, sounded worse to me than the stock product - harsher, 2-D flat and more 'HiFi' for some reason, to get the reviews.. I was told the man was basically a brand-figurehead to wrap an enigma around and he acted the part so very well I recall. Apologies if I have this wrong, but I wasn't ever convinced...

 

[CopperFox]

@amirm I am very happy to see low frequency power measured here, as very commonly amplifier power versus frequency is not described in review measurements and/or product specifications, in spite of being one of the more significant metrics for overall sound quality.

What is the measurement frequency for the "Max power" results here, or is it any specific frequency at all?
It would be useful and interesting to see power measured also at 20Hz, or even some kind of power vs frequency sweep if that is somehow possible. (I would see even the 20Hz information being more interesting for an amplifier than distortion at 1 KHz.)

A power (or current) vs frequency measurement would be something I would personally be very interested in also for headphone amplifiers, even if the comparison would be only at two different frequencies. Power hungry planars are popular, which makes it significant.

 

[AndreaT]

The price is in Bruno’s territory and makes this amp not competitive with a Nilai 500 stereo amp. Yes, it is a diy kit, but a very easy one to build.

 

[amirm]

What is the measurement frequency for the "Max power" results here, or is it any specific frequency at all?

The "max and peak" power ratings are at 1 kHz. I have now added the 40 Hz tone as from my experience, that is a peak frequency in bass for a lot of music.

Note however that people don't tend to drive full range speakers with these amps so we are pushing things by emphasizing 40 Hz response.

 

[amirm]

It would be useful and interesting to see power measured also at 20Hz, or even some kind of power vs frequency sweep if that is somehow possible. (I would see even the 20Hz information being more interesting for an amplifier than distortion at 1 KHz.)

Per my last post, we will really be going outside of the realm of what people do with speakers, even larger ones. That said, this information is already (roughly) present in the various power sweeps vs frequency:

It is the line in orange. Power is about 40 watts. I say "about" because graph resolution is not very high there.

 

[amirm]

A power (or current) vs frequency measurement would be something I would personally be very interested in also for headphone amplifiers, even if the comparison would be only at two different frequencies. Power hungry planars are popular, which makes it significant.

Agree.

 

[LtMandella]

This is a review and detailed measurements of the SMSL VMV A1 Pro GaNFET Class D stereo amplifier (bridgeable into mono). It was sent to me by their distributor, Aoshida audio, and costs US $495.
View attachment 454660
I like the inclusion of volume control and display (there is also a metal remote). Back panel shows the inclusion of power supply which is very nice:

View attachment 454661
I wish trigger input was available. Bridge mode requires changing modes in the menu. When I did that, the amplifier would not produce any output and some red LEDs would be blinking through the back terminals. I tried a few things and eventually gave up. Also, and maybe related, the positive speaker terminal for the right channel was loose.

In use, the amplifier ran very cool, much cooler than its competitors. It mildly got warm to touch. Maybe this is one of the benefits of GaNFET transistor technology.

SMSL VMV A1Pro Amplifier Stereo Measurements
As usual, we start with our dashboard of 1 kHz into 4 ohm load:

View attachment 454662
Distortion and noise are low enough to land the A1Pro in the top of our "competent" category:
View attachment 454663
View attachment 454664

Noise performance is very good:
View attachment 454665
Company frequency response measurements show slight sensitivity to load. I measured more but still less than some other amps without post filter feedback:
View attachment 454666

IMD distortion is within the expected range:
View attachment 454667
View attachment 454668

Crosstalk is not bad either although I expect better numbers in lower frequencies:
View attachment 454669

At 4 ohm, distortion sets in a bit early but noise performance is very good:
View attachment 454670
We do fall short of company specs for power:
View attachment 454672

I was surprised to see a sharp drop in power at 40 Hz:
View attachment 454673
View attachment 454677

This is reflected just the same at 20 Hz in our frequency power sweeps:
View attachment 454674

Amplifier is stable on power up:
View attachment 454675

And may only have a power off pop:
View attachment 454676

Conclusions
Performance of the A1Pro is above average in a number of categories but for the price, it should be that way across the board and it is not. To wit, it should not have load dependency, nor the sharp power drop at lower frequencies. As with a number of GaNFET designs I have tested, the marketing value of the technology seems to be higher than reality. Here, the only benefit seems to be lower power consumption. Otherwise, even IC amplifiers outperform the A1Pro. Those products are messier to use though by having large external power supplies.

I was close to recommending the SMSL VMV A1 Pro but at end, I could not. Company should strive to do better to match the excellence of the rest of their product line.

------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Thank you Amir for the high level of integrity in your reviews, and commitment to the data wherever it leads.

 

[kemmler3D]

$500 for 120wpc needs to come with much better numbers than this in 2025.

 

[Jimster480]

Really doesn't look good

 

[daniboun]

The price is in Bruno’s territory and makes this amp not competitive with a Nilai 500 stereo amp. Yes, it is a diy kit, but a very easy one to build.

You cant compare.... A Nilai mono amp is about $ 850...

 

[srkbear]

I did not. It is a bit of work and I only do that if the rest of the performance is good.

Amir, appreciate the nice review—I’m just a bit puzzled by this one. I recognize this is Class D, but I was under the impression that GaNFET is a fairly legitimate innovation that in theory should narrow the SINAD gap between these switching amps and Class A. The results here also seem to be unusually shoddy for SMSL. Given that you encountered some technical obstacles during setup and a loose terminal, do you think there’s any chance this particular unit could be a lemon?

 

[Guddu]

Amir, appreciate the nice review—I’m just a bit puzzled by this one. I recognize this is Class D, but I was under the impression that GaNFET is a fairly legitimate innovation that in theory should narrow the SINAD gap between these switching amps and Class A. The results here also seem to be unusually shoddy for SMSL. Given that you encountered some technical obstacles during setup and a loose terminal, do you think there’s any chance this particular unit could be a lemon?

Do you mean Class A amplifiers have higher/better SINAD (Better I say "performance") than Class D?

 

[amirm]

I recognize this is Class D, but I was under the impression that GaNFET is a fairly legitimate innovation that in theory should narrow the SINAD gap between these switching amps and Class A.

The transistor itself has some benefits. But if the rest of the circuit assumes standard MOSFETs or doesn't take advantage of their unique value, then you are just paying more for nothing.

 

[Roland68]

Amir, appreciate the nice review—I’m just a bit puzzled by this one. I recognize this is Class D, but I was under the impression that GaNFET is a fairly legitimate innovation that in theory should narrow the SINAD gap between these switching amps and Class A. The results here also seem to be unusually shoddy for SMSL. Given that you encountered some technical obstacles during setup and a loose terminal, do you think there’s any chance this particular unit could be a lemon?

How is GaNFET "technology" supposed to lower SINAD values in an amplifier?
And which Class A amplifiers have lower SINAD values than current TPA325x PFFB/Hypex/Purifi amplifiers?

 

[Chaos01]

Why no mono power measurements? Would be interesting.
I know two of them would be to expensive for the given medium quality, but would be interesting if it reach nearly the power in Specs.

 

[amirm]

Why no mono power measurements? Would be interesting.

Did you not read the review?

Bridge mode requires changing modes in the menu. When I did that, the amplifier would not produce any output and some red LEDs would be blinking through the back terminals. I tried a few things and eventually gave up. Also, and maybe related, the positive speaker terminal for the right channel was loose.

 

[Chaos01]

Somehow i missed that part. Interesting behavior.

 

[Roland68]

Why no mono power measurements? Would be interesting.
I know two of them would be to expensive for the given medium quality, but would be interesting if it reach nearly the power in Specs.

Apart from the error, I could also understand Amir if he didn't test such devices completely in every respect.

The measured values are anything but good for the price. The wattage is surpassed by cheaper devices with better measured values. The power drop at 40 Hz is absolutely ridiculous and, in my opinion, disqualifies the device. Comparing it with a Fosi V3 Stereo with the large power supply quickly raises a few questions, but with the 3e Audio A5/A7, things get even more interesting.

An SMSL A300 has slightly worse measured values, but delivers 400 watts bridged into 4 ohms and almost 220 watts into 8 ohms for €/$150-200.