SMSL VMV A1 Pro Stereo/Mono Amplifier Review

[amirm]

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.

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:

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:

Distortion and noise are low enough to land the A1Pro in the top of our "competent" category:

Noise performance is very good:

Company frequency response measurements show slight sensitivity to load. I measured more but still less than some other amps without post filter feedback:

IMD distortion is within the expected range:

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

At 4 ohm, distortion sets in a bit early but noise performance is very good:

We do fall short of company specs for power:

I was surprised to see a sharp drop in power at 40 Hz:

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

Amplifier is stable on power up:

And may only have a power off pop:

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.

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

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[amirm]

placeholder for specs...

 

[Mort]

Thank you for the review. GaNFET may see it's day, but not today.

 

[Matt_Holland]

Thanks for the review.
I voted poor based on the power sag at 40Hz, not meeting manufacturer power rating and overall performance for the price.

@amirm did you test complex loads at 8/4/2 ohms?

 

[amirm]

@amirm did you test complex loads at 8/4/2 ohms?

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

 

[tktran303]

U GaN Touch This

The Revolution that is, and isn’t GaN​

“New materials always get audiophiles’ hearts racing, much more so than strides in engineering fundamentals. Where would the loudspeaker market be without the perennial parade of new cone materials? They’d be forced to make fundamental improvements, which many people in the industry find challenging. Something similar is happening on the fringes of class D.

Let’s get this out of the way first: yes, GaN FETs are faster and easier to use than silicon. But at home audio power levels, the gap is narrow. 150V GaN FETs are about twice as fast as their much cheaper silicon counterparts. This means that if you drop GaN FETs into an existing class D amplifier, you can only hope to improve distortion by a factor of 2 or so.

But what’s a single-digit reduction, considering that in the past years, we’ve reduced distortion several thousand times using nothing but an extra op amp and a few passives (and, admittedly, reams of formulae)? Furthermore, that reduction goes across the board: distortion from switch timing, output inductor nonlinearity, and power supply noise are all impacted. Whereas the much-vaunted GaN FET improves timing distortion alone, which isn’t even that audible.

This explains why the established players haven’t jumped on the bandwagon. Head over to my competitors at ICE to read their excellent take8. The short rundown is: “When you know what you’re doing, GaN doesn’t really move the needle and is a waste of money. We’ll do GaN for you if you think it helps you sell products, but don’t expect any enthusiasm from us”. Amen.

By contrast, it’s been enthusiastically embraced as a band-aid and buzzword by parties who have little to bring to the table in terms of intelligent design or audio performance. The actual circuits in most commercial GaN-based amplifiers are nothing we wouldn’t have recognized 20 years ago. Often, they are basic open-loop schoolbook amplifiers, with lack of feedback ludicrously a claimed benefit.

This is sad because GaN is a breakthrough, just not one that’s relevant for Hi-Fi and home cinema amps. This changes markedly, and spectacularly so, once you pass 200V. 200V silicon FETs are significantly slower than 150V ones. By contrast, there’s not much of a speed gap between 150V and 600V GaN FETs. While GaN isn’t about to change what audio performance is available, it’s certainly going to change what power level this performance is available at. I can assure you, anything north of a kilowatt, I’d use GaN. Not because it’s magic, but because it’s practical. That’s something to look forward to. Imagine a touring amplifier with audiophile performance…”


Bold: my emphasis
Reference:

Life on the Edge - A Personal Perspective on the Past, Present, and Future of Class D Audio Amplifiers - HomeTheaterHifi.com

The past quarter century of class D developments look strikingly different when seen through the eyes of the audio consumer and through...

hometheaterhifi.com

 

[ninetylol]

SMSL keeps hiking prices while performance stays the same. Honestly, you can get a Fosi V3 with comparable performance for just $80.

 

[Graham849]

SMSL keeps hiking prices while performance stays the same. Honestly, you can get a Fosi V3 with comparable performance for just $80.

Agreed ZA3 makes me happy. Albeit no remote.

 

[Matt_Holland]

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

Thanks. That makes sense especially as 40Hz test is showing weakness in current delivery.

 

[Bleib]

Disappointing considering the price. Has SMSL released any great amps at all?

 

[wwenze]

When I did that, the amplifier would not produce any output and some red LEDs would be blinking through the back terminals.

Is it trying to show which 2 terminals to plug to? Nice feature if so.

I don't really like how manufacturers are limiting bridged mode to XLR-only. What if we don't have any XLR-out? I know it's a cheap way to cheat bridge mode into a normal amp but with all the control electronics inside you'd think they would just add the extra inverter stage.

 

[AaronJ]

SMSL keeps hiking prices while performance stays the same. Honestly, you can get a Fosi V3 with comparable performance for just $80.

True if cost for performance is the primary consideration, but the mini amps from the likes of Fosi have those ridiculous floor warts which to some of us are untenable. I’d rather spend $500 for the box with the built-in power supply.

 

[Roland68]

All these Infineon MERUS-based amplifiers have nothing to do with a so-called "GaN FET" other than the fact that the conventional FETs have been replaced with GaN FETs.
That's nothing more than a marketing gimmick.

The Infineon MERUS technology apparently has limitations that can be seen in all amplifiers based on this technology, and GaN FETs don't change that. The tests of the PA-X, PS200, VMV A1 Pro, RAW-HA1, and A300 clearly show the technology's signature. This may be bearable for the cheaper devices, but for the more expensive devices, there are better and/or cheaper alternatives.

I suspect that the reason for sticking with this technology lies in SMSL's lack of development capabilities in this area, as the amplifiers are very reminiscent of a direct implementation of the Infineon evaluation boards.

A test with the Infineon-based GaN-FET modules/amplifiers from Orchard Audio, which advertise significantly better measured values, would be really interesting. Perhaps the problem isn't with the Infineon technology at all?

 

[anphex]

Too expensive for what it does. FAR too expensive actually.

 

[daniboun]

Is GaN the correct meaning of Good Amplifiers for Neuroses?

 

[dtaylo1066]

Quite frankly, I was expecting far more from SMSL on this one. I gave it a "fine," but felt it was a bit of a stretch in doing so.

 

[ICIETDIYEUR]

For this price you can get two O-NOORUS D3 PRO with better SINAD and built-in DAC...

 

[goryu]

these GaN amps are becoming synonymous with load dependent frequency response. Nearly all use outdated circuits. Hard pass.

 

[ICIETDIYEUR]

Hi goryu


I think that if TOPPING makes a model with GanFETs, the problem of load dependence will not exist and with a better SINAD

At the point where I circled the circuit in orange, a better OPAMP and STYROFLEX capacitors instead of the yellow teardrop ones would surely contribute to a better SINAD thanks to the OPAMP, but above all, a better frequency response thanks to the STYROFLEX capacitors, which are specifically designed for audio applications

There have long been solutions that allow Class A amplifiers to be independent of the load...

This is quite regrettable considering the asking price

 

[daniboun]

At the point where I circled the circuit in orange, a better OPAMP and STYROFLEX capacitors instead of the yellow teardrop ones would surely contribute to a better SINAD thanks to the OPAMP, but above all, a better frequency response thanks to the STYROFLEX capacitors, which are specifically designed for audio applications

Amir's numerous tests have shown that the Op Amps update was a placebo and the same goes for the capacitor updates / tweaks