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Review and Measurements of VMV VA2 Headphone Amp

amirm

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#1
This is a review and detailed measurements of the (SMSL) VMV VA2 Headphone Amplifier. It is on kind loan from a member. It seems to have come out back in 2016 but online sellers are still selling it from USD $96 (Amazon) to $140. So in that sense it competes with the likes of JDS Labs Atom and Schiit Magni.

VMV is SMSL's higher up brand and as such, the VA2 comes in a solid aluminum case that weighs a good bit but otherwise is ordinary:

SMSL VMV VA2 Headphone Amplifier Audio Review.jpg

The volume control can only be grabbed from the top which I found a bit hard to turn and adjust. If the music is too loud all of a sudden, you will have have a hard time lowering its volume as you have to lift your finger when you get to the end of the slot and start over.

The two headphone connectors made me think one had higher gain, and the other, lower gain. Turns out this was a mistake as you see later in the measurements section.

The back panel is simple and has nothing other than an on/off switch, input power and dual RCA line in.

Headphone Amplifier Audio Measurements
Here is our dashboard with unity gain (same output as input voltage):

SMSL VMV VA2 Audio Measurements.png


First distortion product is below 100 dB and sets our SINAD to around that number which is good. It clears the hurdle for 16-bit audio which is the most common thing you will play. Turning up the volume improved the SINAD to 108 dB or so which is nice. Neither is a match for JDS Lab's Atom which clocks at 114 dB.

Signal to noise ratio at full volume was exceptional:

SMSL VMV VA2 SNR Audio Measurements.png


At 50 millivolt the performance is not class leading but still very good:
Headphone Amplifier Signal to Noise Measurement.png


Frequency response was ruler flat (excellent):

SMSL VMV VA2 Frequency Response Audio Measurements.png


Most important thing for headphone amplifier is distortion versus power. Let's start with a high, 300 Ohm load:
SMSL VMV VA2 Power at 300 Ohm Audio Measurements.png


There is no clipping indicating more power could be had if you had a DAC with higher than nominal 2 volt used in the above test.

Switching to 33 ohm which emphasizes current delivery gets us this:
SMSL VMV VA2 Power at 33 Ohm Audio Measurements.png


We hit a wall at nearly half a watt which should be plenty for most headphones but again, falls shy of more than 1 watt with the Atom. Distortion is lower than Schiit Magni 3 but there is less power was the case with 300 ohm load.

Output impedance test shows the truth about what the two headphone jacks are about:

Headphone Amplifier Output Impedance Measurements.png


That's right. The "low" headphone jack simply has a 150 ohm resistor inline with it. This will radically change the frequency response of most headphones so is not a good way to reduce output at all. The "high" jack is fine at 3 ohms.

EDIT:
Adding channel imbalance:

SMSL VMV VA2 Channel Imbalance Audio Measurements.png


Excluding the final drop, the variation is +0.3 dB and -.05 dB. So pretty controlled.

Headphone Listening Tests
I tested the VMV VA2 with Sennheiser HD650. There was plenty of power here driving them to pretty loud levels in the high jack. Switching to low really messed things up so I don't recommend using that connector.

Performance was most excellent with Hifiman HE400i with lots of power, and excellent level of detail.

Conclusions
In a different era before the JDS Labs Atom came to market, this kind of performance would be excellent. Alas, the world has changed and these are no longer state-of-the-art measurements. That said, the subjective and objective performance is more than good enough. The hefty enclosure is definitely a huge step above the Atom although I dislike the volume control on VA2 as I noted.

So overall, a competent design from SMSL here and I can recommend it.

------
Questions, comments, critique, etc. are welcome.

Two of my pink panthers got into a fight over who would be in this review picture. One punched the other and it got a bloody nose so I had to take him to urgent care. Charged it to the credit card so need money when the bill comes end of the month. So please donate generously using:

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solderdude

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#2
The 'Low' output isn't really 'low' it seems.
The output resistance isn't low, in fact it is way too high.
The output is not really suited for low impedance headphones either and certainly not for IEM's.
The gain probably also isn't lower either.
It is only lower in output voltage due to voltage division which lowers the maximum output power, noise level.

I agree ... the Atom is a better choice here.
 

GioF71

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#4
Yes... but as stated in the review, this device has been released years before the Atom.
Which, BTW, is not that easy to buy in Europe again. Shipping costs and custom duties would be very high when buying directly from jds labs.
 

solderdude

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#5
AFAICS the only thing this device and the Atom have in common is that they are both headphone amplifiers in just about the same price class and do not have a built in power supply,.

Metal vs plastic enclosure
vol knob accessability differs.
1 headphone socket vs 2 sockets
weight differs.
On/off switch and method differs.
Gain switch vs no gain switch
Atom has pre-amp function, this one doesn't
Atom has 3.5 + RCA inputs, this one only RCA
Wide range SMPS adapter vs AC adapter.
You don't have to whack the VA2 once in a blue moon ?
US product vs Chinese product with associated representatives and outlets.
SINAD differs
Max output voltage/power differs.
Distortion levels differ (but both below audible limits)
Noise level differs
Usability with IEM's differs

The Atom is avaliable (when in stock) in Europe through various channels but arguably more expensive.

Volpots appear to be of similar quality. There is not much choice here either for manufacturers that want to use cheaper parts to keep costs low.
 

Arnandsway

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#6
It's comparable with the JDS Labs O2 in performance, which is nice to see since the VA2 is around €50. Nice one SMSL :)
 

solderdude

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#7
Indeed, the O2 is portable and can run of batteries though and has 3.5mm sockets instead of 6.3mm
 

daftcombo

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#9
Metal vs plastic enclosure
vol knob accessability differs.
1 headphone socket vs 2 sockets
weight differs.
On/off switch and method differs.
Gain switch vs no gain switch
Atom has pre-amp function, this one doesn't
Atom has 3.5 + RCA inputs, this one only RCA
Wide range SMPS adapter vs AC adapter.
You don't have to whack the VA2 once in a blue moon ?
US product vs Chinese product with associated representatives and outlets.
SINAD differs
Max output voltage/power differs.
Distortion levels differ (but both below audible limits)
Noise level differs
Usability with IEM's differs
.
If this list of characteristics is more important than the fact to be a "headphones amplifier", I can find you a vacuum cleaner that is closer to the Atom than the VA2.
 

RayDunzl

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#10
How do I read the Distortion vs Power graph when it goes "backwards" after (before?) the knee?

1560947591905.png
 

Nango

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#13
This was my very first amp purchase back in 01/2015 when I started using headphones on a more regular basis along with an ATH-AD900X which I sold and bitter regret, btw .......... I like this best with the HD 800's.
 
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RayDunzl

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#14
I think that sort of shape happens when protection starts to kick in after a short time at high power.
That makes sense.

My "protection" pops the breaker out in the garage.
 

Frank Dernie

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#16
That makes sense.

My "protection" pops the breaker out in the garage.
I had Krell power amps when I was working in France. The power from the mains is 3-phase and the house had 3 circuits of 220 volts each one to the kitchen the other two to the rest of the house. If I tried to use the washing machine and dishwasher at the same time it tripped out. I don’t recall the Krells doing it though. It was a very old house and the wiring showed lots of signs of DIY tomfoolery.
 

restorer-john

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#19
I like the unit. You could always change the knob to something that sticks out the front or just pull it forward on the shaft to protrude enough to turn it more easily.

Maybe the 'low' and 'high' are referring also to damping. Bear also in mind, the full range of the volume pot can more likely be used in the 'low' setting and S/N will likely improve significantly with higher impedance headphones.
 

amirm

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