SMSL PA-X Stereo Amplifier Review

[abrcdbra]

I come from China. Regarding toppings and smsl, we have a greater preference for smsl. The indicators for toppings are better, but smsl generally receives better feedback in terms of sound quality. In the early days, smsl was also very focused on static indicators, which aligns well with the tone of this forum. This forum is primarily focused on indicators, but it later shifted, now emphasizing dynamic sound quality, and it is very popular in China.

Both the B200 and the PA-X have specific "childhood illnesses". Rather, this is due to the fact that your developers have no experience ("school") in developing sound devices.
The PA-X, for example - the output stage and power supply quite well done. But the small-signal input circuit is a complete disaster. Using the ancient (but cheap))) and terribly slow NJM2068 OPA to convert a balanced signal to an unbalanced signal, after erasing the name, is top marketing))).
But that's not the main thing that's messing with the sound. Chinese engineers chose the worst of all TI's volume control chips, which was originally designed for wearable devices.... Why was it difficult for them to use the PGA2320, which is designed for professional stationary equipment?
Yes, getting 75 dB of amplifier channel separation from chips with a claimed separation of more than 100 dB requires a lot of serious effort. ))
These are just some of the problems with the PA-X.

The B200 has its own shortcomings, also obvious to experienced engineers, which clearly limit the sound quality, including in terms of dynamic characteristics. ))

 

[Evo42]

We often conduct blind tests as part of a project.
In direct comparisons, none of the SMSL Infineon GaN amplifiers (PA200, PA-X, VMV A1 Pro, PA400) have been able to compete with amplifiers like the Sabaj A30a, Topping PA5, B100, Purifi, etc. and convince us.
We focus most on the reproduction of the instruments as we know them.
Among other things, we also noticed the load-dependent behavior with different speakers, which is not the case with any of the other amplifiers.

Especially when it comes to amplifiers, GaN is currently nothing more than a marketing gimmick.
Especially with constantly changing loads, the advantages of GaN, which are undeniable under continuous, permanent load, collapse. As a result, the actual advantage of better energy efficiency is only 0.5-1%, but usually less. It may even be that other Class D designs are more efficient, but I haven't seen any measurements of this yet.
In any case, other leading amplifier manufacturers have decided against using GaN technology in their power amplifiers after extensive testing.

Marketing also suggests that these are special GaN amplifier developments.
In fact, this is the standard Infineon MERUS Class-D controller technology, which can be equipped with either extremely low RDS(on) power MOSFETs or GaN transistors. Since Infineon itself only acquired GaN technology two years ago and the current Merus controllers existed before then, everyone can draw their own conclusions about "specially developed GaN amplifiers."
It should be no secret by now that the SMSL GaN amplifiers (as is unfortunately often the case with SMSL) are based on the manufacturer's evaluation boards.

By the way, a true and comparable comparison of conventional Class D technology based on Merus controllers with power MOSFETs with extremely low RDS(on) and alternatively GaN transistors would be no problem at all, since they are the same controller. For this, SMSL would only have to equip one device with the power MOSFETs.
As a manufacturer, I would have done exactly that first to demonstrate the significant differences, but for that to happen, the significant differences would have to exist.

The much cheaper A300 demonstrates that even conventional Merus technology without GaN is very energy-efficient. Two bridged A300s deliver over 2 x 400 watts into 4 ohms and 2 x 200 watts into 8 ohms, as measured by Amir.

Very informative post thank you. Was looking at getting smsl pa400 but it has discouraged me unless in the unlikely case they have changed the design. I will stick to my original plan of getting a purifi power amp when I can justify the upgrade or perhaps they come down in price a bit. Every option is still in the $2000aud range at the moment with cymax seeming to be the best value.

 

[Roland68]

Very informative post thank you. Was looking at getting smsl pa400 but it has discouraged me unless in the unlikely case they have changed the design. I will stick to my original plan of getting a purifi power amp when I can justify the upgrade or perhaps they come down in price a bit. Every option is still in the $2000aud range at the moment with cymax seeming to be the best value.

That shouldn't deter you from buying, I just don't think it's right that GaN technology is being used to create a false sense of performance that, in this case, doesn't actually offer any real benefit.
Furthermore, the measured values are no better, and in some cases even worse, than those of a 30-year-old NAD 2200 power amplifier, except for the power consumption.

The PA400 (SMSL device) appears to be identical to the PA-X (Shenzhen Audio device), as these devices are often housed in different enclosures for different distribution channels. Therefore, I don't expect any different test results. Anything else would surprise me.
I would also be interested in a repeat of Amir's test and whether the device lasts until the end.

Alternatively, take a look at the Sabaj A30a. I now have two, and it's been keeping me from firmly planned amplifier purchases in the mid-four-figure range for over two years. The fact that you don't need an additional DAC is another advantage, as is the over 200 watts at 4 ohms (measured power).

 

[Evo42]

That shouldn't deter you from buying, I just don't think it's right that GaN technology is being used to create a false sense of performance that, in this case, doesn't actually offer any real benefit.
Furthermore, the measured values are no better, and in some cases even worse, than those of a 30-year-old NAD 2200 power amplifier, except for the power consumption.

The PA400 (SMSL device) appears to be identical to the PA-X (Shenzhen Audio device), as these devices are often housed in different enclosures for different distribution channels. Therefore, I don't expect any different test results. Anything else would surprise me.
I would also be interested in a repeat of Amir's test and whether the device lasts until the end.

Alternatively, take a look at the Sabaj A30a. I now have two, and it's been keeping me from firmly planned amplifier purchases in the mid-four-figure range for over two years. The fact that you don't need an additional DAC is another advantage, as is the over 200 watts at 4 ohms (measured power).

I was interested in the sabaj but seems there is very limited availability and where available pretty expensive. I wonder if they will make a successor?

 

[Alexx]

I'm interested in the Sabaj A30a.

Do you know if it has an auto-start system?

Is it possible to use it as a power amplifier driven by the Wiim Ultra? Alternatively, I can use the Wiim Ultra as a "multi-source" and connect it to the Sabaj via RCA or coaxial.
Thank you very much.

 

[Roland68]

I was interested in the sabaj but seems there is very limited availability and where available pretty expensive. I wonder if they will make a successor?

These devices are always produced in batches. It's possible that the last batch is currently running low. Only Sabaj knows whether and when the next batch will be produced, or whether there will be a successor. However, A30a models are currently still available, at least in the EU at normal prices.
Alternatively, you can also look for an identical SMSL VMV A2; sometimes it's only slightly more expensive on sale.
In some cases, it might be worth waiting until the Black Friday sales or looking for a used device.

 

[Roland68]

I'm interested in the Sabaj A30a.

Do you know if it has an auto-start system?

Is it possible to use it as a power amplifier driven by the Wiim Ultra? Alternatively, I can use the Wiim Ultra as a "multi-source" and connect it to the Sabaj via RCA or coaxial.
Thank you very much.

The Sabaj amplifier is ideal for Wii M devices, but the two devices should only be connected digitally.

It doesn't have an auto-start system like a 12-volt trigger.
If you power it on via a power strip, it will turn on.

 

[Evo42]

These devices are always produced in batches. It's possible that the last batch is currently running low. Only Sabaj knows whether and when the next batch will be produced, or whether there will be a successor. However, A30a models are currently still available, at least in the EU at normal prices.
Alternatively, you can also look for an identical SMSL VMV A2; sometimes it's only slightly more expensive on sale.
In some cases, it might be worth waiting until the Black Friday sales or looking for a used device.

I have reached out on the sabaj AliExpress store. Interesting with the VMV. Although they both are pretty close to purifi money the moment.

 

[Roland68]

I have reached out on the sabaj AliExpress store. Interesting with the VMV. Although they both are pretty close to purifi money the moment.

Which Purifi do you mean exactly?

 

[Evo42]

Just one of the implementations of the purifi 1et6525sa module

 

[Alexx]

@Roland68
Great, thank you so much.

No problem connecting to the digital output (but this way I'm using the Sabaj DAC, or am I wrong?).
Thanks again.

 

[Roland68]

@Roland68
Great, thank you so much.

No problem connecting to the digital output (but this way I'm using the Sabaj DAC, or am I wrong?).
Thanks again.

The A30a does not have a DAC because it is a completely digital amplifier that converts the digital signal at the output directly into PWM.

 

[Evo42]

Just got confirmation that the Sabaj A30a is discontinued.

 

[MBO]

I think there's a misunderstanding regarding the PA-X; it's an almost pure mono amplifier, and measurements should only be taken in mono mode. It apparently has poor mixer op-amps in the balanced input. In mono mode, it runs directly balanced, and only then does the amplifier achieve its optimal sound quality. The SMSL GaN amplifiers are obviously pure balanced mono power amplifiers with a stereo option.

 

[Roland68]

I think there's a misunderstanding regarding the PA-X; it's an almost pure mono amplifier, and measurements should only be taken in mono mode. It apparently has poor mixer op-amps in the balanced input. In mono mode, it runs directly balanced, and only then does the amplifier achieve its optimal sound quality. The SMSL GaN amplifiers are obviously pure balanced mono power amplifiers with a stereo option.

You're mistaken. All SMSL Infineon GaN amplifiers are based on the same single-ended, two-channel (stereo) evaluation board, albeit with different power ratings and power supplies.
For mono operation, the two stereo channels are simply connected using BTL coupling. This applies to the PA-X as well as the internally identical PA400 and the smaller models.
It's essentially a standard Class D stereo amplifier where the stereo channels are combined via BTL for mono operation.

 

[MBO]

You're mistaken. All SMSL Infineon GaN amplifiers are based on the same single-ended, two-channel (stereo) evaluation board, albeit with different power ratings and power supplies.
For mono operation, the two stereo channels are simply connected using BTL coupling. This applies to the PA-X as well as the internally identical PA400 and the smaller models.
It's essentially a standard Class D stereo amplifier where the stereo channels are combined via BTL for mono operation.

I say something different: SMSL designed its amplifiers as a balanced mono BTL circuit design; stereo is secondary here, and mono operation would be optimal.

 

[Roland68]

I say something different: SMSL designed its amplifiers as a balanced mono BTL circuit design; stereo is secondary here, and mono operation would be optimal.

SMSL didn't design anything here. Infineon designed the circuit, and SMSL adopted it for their amplifiers. Infineon's documentation is freely available, and you can compare the circuit and components yourself. The similarity is certainly not a coincidence.

So, there's nothing special about it, and nothing that SMSL designed specifically for it. The symmetrical drive is achieved by connecting two of these amplifier channels via BTL coupling.

Whether this amplifier actually has better measurements in mono operation will be revealed when Amir, or someone else, measures a PA-X or the identical PA400 that doesn't fail during these standard tests.

Otherwise, it would be great if you could post measurements or technical information to support your statements.

 

[jahjahjah]

My opinion, anyone that doesn't buy this amp because of this review is really missing out. I had 45 days to return my purchase and every day as I listened to it, going through my reference material. I just fell more in love with it. I didn't think my speakers were capable of playing like this. I have had a lot of amps try to step up with this same setup, this one does. My speakers are manufacturer rated at 6 OHM. This amplifier likes to be set at 4 Ohm. This amp barely gets warm at the highest volume I will ever play it at. Another weirdness, I have tinnitus, normally loud music usually sets it off. not this amp. No detectable sibilance. Very comfortable. Many listening reviews you can watch, so I won't go on.

 

[kyuu]

Another weirdness, I have tinnitus, normally loud music usually sets it off. not this amp. No detectable sibilance. Very comfortable. Many listening reviews you can watch, so I won't go on.

Assuming you are actually hearing anything, and aren't a shill, the only explanation there is the amp's high frequency roll off at 4 ohms. You can replicate that with a simple PEQ filter, you don't need to buy an amp that has it built in.

 

[jahjahjah]

Assuming you are actually hearing anything, and aren't a shill, the only explanation there is the amp's high frequency roll off at 4 ohms. You can replicate that with a simple PEQ filter, you don't need to buy an amp that has it built in.

Well, I am old, 73. However, I have had my hearing tested regularly, with less than normal hearing loss at my age.. The sound was not noticeably different at 4ohm or 8ohms. I never needed to buy any of the many amps and speakers I have bought over the years. I have often just been looking for for more detail or sound stage improvements. I can't explain why I can hear more detail in the female vocal range and better realistic sound staging. I am certainly not a shill for anybody, I have bought all my equipment at retail pricing. Go watch the reviews that people that are listening to their ears have come up with. That is why I decided to try this amp and it is replacing a much more expensive one now. Back to back comparisons, came out on top for P-AX. I assumed the sibilance issue on some albums was my speakers, but it disappeared with P-AX. Not disputing the specs, assuming the units reviewed are equivalent. I like specs a lot too, but ultimately what I can listen to at various volumes and for long sessions and walk away still crazy about a piece of gear, is what I like. Last year I replaced my preamp and my DAK, and cartridge, and did some listening room revisions. This year, will probably build some kit speakers and compare with my current factory manufactured ones. I don't keep equipment around, once it gets superseded, I move on all the way back to when I was building amps from scratch. I can understand why you commented and it doesn't bother me, thanks for the reply, but I said it in the first sentence, listen with your ears, and if you have a problem, then go after the specs. If you go by specs alone, you are missing out because there is no way at this time to test the actual sound of a piece of equipment other than the human ear. It's like if you took the specs for different cars and then tried to guess what the road feel is like from those without actually driving.