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SMSL SA400 Review (Power Amplifier)

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I am not sure how much of this is temporary given the world order with component shortages, high shipping costs, etc. but to me, the better retail target would be $499. The warranty is short at 1 year as well.
/
Funny that you say that, the launch price for this amp in China(Taobao) is 3000RMB = USD470, and it would be on sale at 2550RMB = USD400 on Taobao's 6/18 sale.

Not sure who sets the international price, SMSL or shenzhenaudio, but someone obviously hiked it up too much.
Thanks for the review!
 

Loaw

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SMSL passes the buck to Shenzenaudio for support with their products. This message was posted in one of the threads discussing issues with SMSL's products:

Dear Customer,
Thanks for your email.
Questions regarding the SMSL SU-9.
Kindly contact with SHENZHEN audio support team,
[email protected]
[email protected]


They are sole agent for this model and will give a reasonable suggestions.

Best regards
S.M.S.L Audio


I'm not sure why they bother sending the above message since @SHENZHENAUDIO do not reply to emails.
I haven't purchased SU-9, but I asked for a positive after-service from them before. I think Facebook is a good way to access it.
 

bigjacko

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I can see how it cost USD 400 or even 470, but at 650 this is no go for me. I think they are going in the wrong direction, the cost to performance ratio should be their goal but now they don't want to sell cheap. I guess shenzheng audio and topping are involved in this. Topping probably has an amp coming out in not distant future, and the cost to performance ratio will be the same here. They slowly want to charge more and more, I get why they do this, but at some point some people will turn away, just depend on how much they can take. The golden age for stereo amp is not now, might be two or three years after when they came up with more stereo amps with even better performance and cheaper price.
 

VintageFlanker

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I wonder how this stacks up against some of the lower priced Hypex amplifiers based on the NC252 single board solution.
We already know. This is worse, appart from THD+N Vs Frequency.

Why don't expose a digital input if internally it works digital?

Because they do need to sell M400 and SU-9 DACs.;)
 
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Mulder

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It is better to get the Hypex 252NC module based Audiophonics one over this I presume, if you aren't too much bothered about the one box solution aspect :)
Leaving the "one box solution" aside, and if balanced input is not needed, I even think the XTZ EDGE A2-300 is a better buy.
 
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amirm

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Why don't expose a digital input if internally it works digital?
It is a raw digital interface so they would have had to put transceivers in there for Toslink/Coax which would add cost and take up space in the back. USB would be much more complicated and costly.

But yes, at high level would have been nice to have a digital input as that may have improved signal to noise ratio and provided more bandwidth.
 

dmac6419

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I can see how it cost USD 400 or even 470, but at 650 this is no go for me. I think they are going in the wrong direction, the cost to performance ratio should be their goal but now they don't want to sell cheap. I guess shenzheng audio and topping are involved in this. Topping probably has an amp coming out in not distant future, and the cost to performance ratio will be the same here. They slowly want to charge more and more, I get why they do this, but at some point some people will turn away, just depend on how much they can take. The golden age for stereo amp is not now, might be two or three years after when they came up with more stereo amps with even better performance and cheaper price.
Looks like they're passing the shipping cost to the customers Topping will most likely do the same,shipping costs money.
 

Eleo

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First of all, thanks Amir for this very interesting review. Then a question, if everything inside gets digitalized what is the point of pairing this object with a top-class dac like M400 or SU-9? I understand that they want to sell both of them but perhaps they or someone else like Topping could deliver an amp with better specs and digital inputs. It would really be a game-changer.
 

abdo123

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At 700$ Class D I expect Hypex level of performance to be honest.

And they delivered…ish

Seems like a great product.
 
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bud947

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Nice review and good results. Perhaps a SMSL DA-9 or Sabaj A20a review ?
SMSL is asking too much for this unit as it compete with Hypex 252NC. Also their choice for STA516BE is questionable as it's an quite old chip, I understand they were looking for power (vs Infineon used in DA-9) but TPA3255 has plenty of power and would have yield better results from AX5689.
Anyway this review proves that SMSL (and other chinese ?) electronic design are really improving at fast pace, maybe too fast ? (people are getting more QC issues).

I hope we'll get a review for the yet to be released SMSL VMV A2 as it look promising https://www.l7audiolab.com/f/smsl-vmv-a2-amp/
 

GGroch

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I wish there was a standard for including acoustic noise like coil whine into amp measurements. It obviously effects S/N in real world use.

Certainly its impact varies depending on distance from the amp and speaker volume. Nevertheless, if factored in there would be instances where whine or fan noise significantly exceed electronic noise.
 

Francis Vaughan

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The marketing material for SA400 shows a digital feedback but I don't see that in the ST specs. I am not clear if this is an addition by SMSL or it is part of ST amplifier chip that they don't talk about.
This is a trifle mysterious. The STa516BE isn't a complete amplifier. It is just the power output stage. It requires a modulator to create the PWM control. ST make a couple of fully integrated modulators, the obvious one being the STA321. This device has both analog and digital imputs and provides the full monty of tone controls and volume control, all in the digital domain. But it is clear that the SMSL 400 doesn't use digital volume or tone controls. They proudly use the JRC NJW1119A tone control and NJW1195 volume control, which are analog domain controls.
This suggests that SMSL have implemented a different modulator to the standard ST parts.

In the pic below from the marketing material the STa516BE is the box labelled Power Stage. The rest is SMSL. They are very coy about what is going on here. It is a hybrid negative feedback loop. There is much black magic here. Use of real true negative feedback is challenging to say the least. Stability is going to be a slippery beast. Hypex have patent *
on how to do it that derives from their research on self oscillating PWM amplifers (basically transforming their analog topology into a digital dual.) How SMSL does it would be very interesting to know.

The diagram however shows a digital input to the system. That isn't consistent with the use of the analog volume and tone control chips. So one suspects there is a lot more that the marketing doesn't get quite right.

A pic of the internals would be most welcome.

*Editing to correct this. It isn’t a patent but a paper. The paper is cited in the patent Axign have.
  • Mouton, Toit , et al., “Digital Control of a PWM Switching Amplifier with Global Feedback”, AES 37th International Conference, 2009, 1-10.
et al is Bruno Putzeys.

202105281517336922.jpg
 
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bud947

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@Francis Vaughan thanks for your explanation. It's clear that this marketing material doesn't tell everything and the arrows directions are not true...

I think that the STA516BE power stage is used with STA321(or similar) as PWM and Digital Loop Filter being AX5689.
STA321 provides analog inputs so tone and volume control are processed before signal is handled to the PWM stage (https://www.st.com/en/audio-ics/sta321.html). Digital Input of AX5689 is only used as a digital feedback loop once ADC digitize the analog signal.

A picture of the inside would be welcome!
 
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