SMSL PA-X Stereo Amplifier Review

[amirm]

This is a review and detailed measurements of the SMSL PA-X GaN based Class D stereo amplifier. It was sent to me by Shenzhen Audio and costs US $699.

The PA-X is gorgeously designed. It would look even better with the display on, had I not damaged the unit in testing (see below). A volume control IC is used allowing use of remote control:

I wish SMSL would include trigger functionality. The unit weighs a "ton" for its size, oozing feeling of quality.

If you are not familiar with my amplifier measurements, please watch this tutorial:

SMSL PA-X Amplifier Measurements
With balanced amplifiers, I start with that input:

Usually that produces better performance but not in this case as RCA does better:

Likely some kind of conversion is performed from balanced to unbalanced (due to volume control IC?), degrading performance. Either way, the PA-X scores well when it comes to noise and distortion:

At the bottom is one of the first GaN based designed I tested. So not bad at all.

We can see the better noise figure for RCA input with our SNR tests:

Frequency response shows some load dependency. It is manageable but at the cost of 4 ohm roll off:

Crosstalk performance is a bit disappointing in the way it gets worse with lower frequencies. Usually it is the other way around as we see from our references:

Multitone performance is good:

Due to increasing distortion at higher frequencies, 19+20 kHz intermodulation distortion test shows worse performance (typical):

PA-X more or less meets is power specs:

There is a curious menu option to set the load to 4 or 8 ohm. It has no impact on the testing above, but does boost the power for 8 ohm:

At this point, I ran my FTC like power sweep where the amplifier is repeatedly pushed into clipping in order to generate the max power possible at 1%THD. The sweep starts from right and goes to the left:

Measurements stopped around 40 Hz. I looked at the amp and it had shut down. This is typical as many amps will complain and turn off. Alas, the PA-X would no longer power on. I waited a while until it cooled off and it still doesn't power on. I will test it again tomorrow but I suspect it is permanently damaged.

As I have said countless times, such stress times can damage amplifiers for no good reason. No one is going to push an amplifier into clipping for such extended amount of time as I did above. And at any rate, there is little industry awareness that such tests need to be passed. So to some extend, I feel responsible for damaging the unit.

Amplifier is stable on power up:

Conclusions
Other than the frequency response droop, the PA-X performs well and looks gorgeous while doing it. With the data we have, if it had not been damaged, I would have likely recommended it. As is, I am sitting here with a sense of regret.

My appreciation to Shenzhenaudio.com for sending the amplifier in for testing.

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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/

 

[xevman]

Was curious as to how this was going to perform, I sort of expected it to be closer to the state-of-the-art category and was definitely considering it. Alas, I guess I will be buying a Yamaha R-N800A next month and can stick with a one box solution.

 

[Mort]

Putting aside the unit failure, these features and measurements seem very meh for $700.

• No trigger
• RCA better than balanced
• Fine but not great sinad
• Frequency droop
• Power specs slightly under
• Crosstalk

Given the state of the industry, this is a hard pass.

 

[beeface]

RIP this amplifier. My thoughts are with its family

 

[JSmith]

SMSL PA-X GaN based Class D stereo amplifier

Cheers for the testing Boss.

Some pics (from marketing);

JSmith

 

[HighFutility]

Was curious as to how this was going to perform, I sort of expected it to be closer to the state-of-the-art category and was definitely considering it. Alas, I guess I will be buying a Yamaha R-N800A next month and can stick with a one box solution.

Wiim Pro has EQ if you want a one-box solution.

 

[Rja4000]

Thanks for this review.

I'm a bit confused with the 8 ohm power plot.
Is the power really higher for 8 ohm than for 4 ohm ?
I suppose it's just the menu toggle on 4 ohm position, but both measured with a 8 ohm load ?

Still, this power under 8 ohm is huge.

 

[xevman]

Wiim Pro has EQ if you want a one-box solution.

I want multiple analog inputs for my tape deck cd player and turntable.

 

[amirm]

Is the power really higher for 8 ohm than for 4 ohm ?

No, no. In that test, the load is always 8 ohm. The amplifier has an option of "load type = 4" or 8 ohm. That is the difference I am showing. It might be increasing the voltage rails if it knows the load is 8 ohm and with it, produce more power at 8 ohm. Total power was about 170 watts with 8 ohm which is lower than 205 watts at actual 4 ohm load.

 

[PristineSound]

If an amplifier can't handle torture tests or does not have enough safeguards built in to prevent damage then it's not a well engineered amplifier imo. Although, that does not mean it's a no buy, it just means you need to know what you are buying.

You should not feel guilty, I consider reliability as part of the test.

 

[GWolfman]

I agree with an earlier comment that this seems too expensive for what it provides. One will have to decide if looks alone are worth the cost.

As always, Amir, thanks for the review!

 

[xanalog]

Thank you for the review, @amirm,
Was it intentional to not provide polling/voting?

Woooh, GaN but HappyPanther.

 

[GD Fan]

Was really hoping to read this review after the hockey playoff games - until I saw the comment about the unit being damaged in testing. That beats first round playoffs any day.

 

[phoenixdogfan]

Amir, you killed that amp! Well, at least it wasn't something that darted out from between two parked cars.

In any case, the results are surprising to me. When I see either SMSL or Topping, I expect the product is going to have a SINAD of at least 125 and is going to cost no more than $125, so definitely a let down there. But good to know what this unit is capable (or not capable) of in any case.

So thanks for the review anyway. And I'm sure it didn't suffer, so there's that.

 

[Old_School_Brad]

If the amplifier failed, the real issue lies in the lack of built-in protection -ultimately, that’s on the manufacturer.

The "FTC-like" test isn’t particularly extreme, and no well-designed amplifier should be taken out by it. If it is, that points to shortcomings in engineering.

So I wouldn’t carry any guilt here. The responsibility lies with the manufacturer for not incorporating adequate safeguards.

 

[capslock]

Yeah, just like the Topping B100 that shuts off (needing a cumbersome reset procedure) or even fails permanently at nowhere near its rated power. Has that been fixed in newer revisions?

 

[amirm]

Thank you for the review, @amirm,
Was it intentional to not provide polling/voting?

Woooh, GaN but HappyPanther.

Yes. I figured since it broke, it wouldn't be fair to subject it to polling. I could add it though.

 

[GD Fan]

Yes. I figured since it broke, it wouldn't be fair to subject it to polling. I could add it though.

Any word from the company regarding the test?

 

[pma]

Another example of bad amplifier design, namely protection circuit in this case. The amplifier must withstand such test. And the reviewer even tries to find apologies for such behaviour. Another issue is output impedance, ASR should do this basic measurement. 4/8 ohm resistive load plots do not tell to inexperienced reader that output impedance at high frequencies would be above 1 ohm.

 

[xanalog]

Yes. I figured since it broke, it wouldn't be fair to subject it to polling. I could add it though.

Not on my account. I could withdraw my vote, if you wish!