• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

SMSL SA400 Review (Power Amplifier)

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
34,572
Likes
125,329
Location
Seattle Area
#1
This is a review and detailed measurements of the SMSL SA400 switching desktop power (speaker) amplifier. It was sent to me by the company for testing and costs US $660.

The SA400 is a powerful amplifier yet it comes in the same compact SMSL package and UI you would find in their desktop amp:

SMSL SA400 Review Bluetooth Amplifier.jpg


Amplification is provided courtesy of ST Micro STa516BE. 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. Either way the input to the amplifier is digital so even though we have analog inputs, they need to be digitized to be used internally:

SMSL SA400 Review Bluetooth balanced back panel Amplifier.jpg


A resonant LLC switching power supply provides the heft juice needed to drive this amplifier in a small package.

Bluetooth input is provided as well as a subwoofer output with low pass filter. In addition, tone controls are included using a dedicated JRC chip.

There is an informative temperature measurement you can turn on which I did as you see in the picture above. With normal music listening (one channel) the unit stay pretty cool. In testing however, the case got fairly warm and the display indicated 58 degrees C. I suggest not stacking anything on top of SA400.

One issue is a mechanical whine from an internal coil. I can hear it even when nothing is playing from about 1 foot or so. When testing at higher powers, this became much louder but when playing music, you won't be able to hear it most likely.

SMSL SA400 Measurements
There are three gain settings but performance is very similar between them. I adjusted high gain for 29 dB which is my standard (defaults to 30 dB):

SMSL SA400 Measurements High Gain Integrated Amplifier.png


SMSL SA400 Measurements Medium Gain Integrated Amplifier.png


SMSL SA400 Measurements Low Gain Integrated Amplifier.png


For the rest of my testing I used the adjusted high gain for better comparison to other integrated amps adjusted the same way.

Distortion is around -90 dB but what pulls down SINAD is the rather high noise floor. This causes the overall ranking to be just slightly above average:

Best desktop stereo amplifier.png


Indeed we can see the noise issue in our SNR measurements:

SMSL SA400 SNR Measurements High Gain Integrated Amplifier.png


State of the art amplifiers get 16 bits of dynamic range at 5 watts so we are two bits short here. Even at full power you are adding noise to a 16 bit signal (you want your amp to be cleaner than the noise in the source). This, and the fact that there is no bandwidth above 20 kHz nukes any idea of playing high-res content:

SMSL SA400 Frequency Response Measurements High Gain Integrated Amplifier.png


Sure would have been nice to use an ADC that was running at 48 kHz, not 44 as it seems to be. Use of the ADC is likely the reason the noise floor is higher than it would be otherwise. We have seen this in AV receivers which likewise digitize their analog inputs (unless you put them in "native" mode).

There is some very good news though. The feedback for the amplifier is taken post filtering which means it can compensate for the interaction between that filter and the load. The above measurement shows actually two graphs: one at 8 ohm and the other, 4. Both land on top of each other showing the amp doesn't care which is great. We only see this in the best class D amps like Hypex Ncore and Purifi.

Crosstalk was very good but unpredictable:

SMSL SA400 Crosstalk Measurements High Gain Integrated Amplifier.png


You can see the normal trend in the other two amps (dashed lines).

Most important test for any amplifier is how much power we have and how much distortion and noise so let's look at that at 4 ohms:

SMSL SA400 Power into 4 ohm Measurements High Gain Integrated Amplifier.png


This is a powerful little amp, producing nearly 500 watts of power especially if you allow some peaking:

SMSL SA400 Peak Power into 4 ohm Measurements High Gain Integrated Amplifier.png


It complies with the spec which I think is 220 watts. Power naturally drops at 8 ohm but still healthy:

SMSL SA400 Power into 8 ohm Measurements High Gain Integrated Amplifier.png


On our last test which is power versus distortion+noise at different frequencies. The output was quite unique:

SMSL SA400 Power into 4 ohm versus frequency Measurements High Gain Integrated Amplifier.png


I have not seen a power amplifier show this level of frequency independence. Yes, having only 20 kHz bandwidth helps but still, even linear amplifiers don't produce such dead straight and sameness the SA400 is producing. This is quite excellent.

Note that the the amp went into protection at both 20 kHz and 20 Hz in this sweep. Alas there was no indication on the display. I had to power cycle the unit to get it to work again.

SMSL SA400 Amplifier Listening Tests
Even though I listen to every headphone amplifier, I only do so rarely for power amplifiers. I decided to start doing listening tests with this amplifier which was a good thing. I used an Infinity 253 speaker for my testing. Despite driving only one channel, the SA400 drove the R253 with extreme authority and clarity. Tons of detail and dynamics with little else to wish for. Putting my ears next to the tweeter I could hear a slight hiss but a few inches away it would disappear. The sound was so enjoyable I am still listening to it as I type this!

Conclusions
SMSL brings us an interesting and unique power amplifier to us. Love the load independence and small packaging plus tons of power. Performance drops to average levels in some areas but nothing that appears to be faulty or poorly engineered. I guess my one reservation is the cost. 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. For DACs and such I am not worried about warranty much but for amps I do like to see longer warranty.

Overall, I am going to put the SMSL SA400 on my recommended list. It delivers tons of power with no weak points.

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

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

pozz

Data Ordinator
Forum Donor
Editor
Joined
May 21, 2019
Messages
3,497
Likes
5,556

franspambot

Addicted to Fun and Learning
Forum Donor
Joined
Mar 30, 2019
Messages
673
Likes
1,492
#5
That one channel being much more distorted in the 4ohm graph bothers me. Is it related to the issue found in the M500 and SU-9 being discussed in multiple threads right now? I agree with you that the price is waaaaay too high for this product, especially as it's from a company seemingly always putting out fires. (How many issues has the M500 had??? Not that companies like Topping are any better.) But, really, I may as well save up a little bit more and get something like a Buckeye Hypex amp for that money. As an SMSL product owner I am learning the value of peace of mind.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
34,572
Likes
125,329
Location
Seattle Area
Thread Starter #7
That one channel being much more distorted in the 4ohm graph bothers me.
It is a common thing in amps. Usually one channer is farther from the power supply than the other and has some voltage/current modulation. While it is better to not have it, I don't loose a lot of sleep over it.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
34,572
Likes
125,329
Location
Seattle Area
Thread Starter #8
When you tried to run the max power test, did it shut down?
It did but that is because the max power test jumps up and down until it zeros in on the max power. This doesn't work with amps that have quick protection systems like these chip amps tend to do. I could mess with it enough to get something but wasn't worth it.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
34,572
Likes
125,329
Location
Seattle Area
Thread Starter #9
The coil whine is a concern. I would be concerned about buying one that may have this issue since @SHENZHENAUDIO has a poor reputation for after sales support. See this thread as an example:

https://www.audiosciencereview.com/...nge-smsl-m500-high-3rd-harmonic.22710/page-32
SMSL or Shenzhenaudio? That thread is about the former I thought.

But yes, you may want to see some mileage on this amp before jumping in. I was going to put a notice in the review but forgot. :)
 

YSC

Major Contributor
Joined
Dec 31, 2019
Messages
1,361
Likes
923
#10
decent performance from a small and integrated amp for passives, though after lurking here I have been always appreciating the C/P ratios of the nice actives can do than going the combo route.
 

Massimo

Active Member
Joined
Jul 5, 2019
Messages
117
Likes
104
#11
SMSL or Shenzhenaudio? That thread is about the former I thought.

But yes, you may want to see some mileage on this amp before jumping in. I was going to put a notice in the review but forgot. :)
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.
 
Last edited:

GWolfman

Active Member
Forum Donor
Joined
Nov 3, 2020
Messages
297
Likes
330
#12
Thanks.

Agree on cost being too high for what it offers. Nice and compact though...
 

Xulonn

Major Contributor
Forum Donor
Joined
Jun 27, 2018
Messages
1,407
Likes
3,986
Location
Boquete, Chiriqui, Panama
#15
Interesting that 18 vendors at AliExpress sell it at exactly the same price, although some offer free shipping, and others charge a lot.
===============================


Aliexpress-SMSL-SA400.jpg
 

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
1,171
Likes
1,157
#17
So subwoofer output with low pass, is there a way to customize this low pass? at least the cutoff? If not what is it? digitized input calls for a great opportunity for dsp, and at this price point vs performance, it should allow for some, even if it’s just some basic EQ possibility.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
34,572
Likes
125,329
Location
Seattle Area
Thread Starter #18
So subwoofer output with low pass, is there a way to customize this low pass?
I have not tested it. This is what they show:

 

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
7,397
Likes
19,174
Location
Gold Coast, Queensland, Australia
#19
The crosstalk/separation plot issue could be measurement. @amirm how does the AP handle that test? Left into right, right into left or does it sweep one channel only and measure the residual in the undriven channel vs frequency? The jumping up and down, suggests to me the undriven amplifier channel was muting periodically as it might with no signal. That would give a good crosstalk number until it unmuted again.
 
Last edited:
Top Bottom