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SMSL A100 Review (Stereo Amplifier)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 30 18.2%
  • 2. Not terrible (postman panther)

    Votes: 96 58.2%
  • 3. Fine (happy panther)

    Votes: 37 22.4%
  • 4. Great (golfing panther)

    Votes: 2 1.2%

  • Total voters
    165

amirm

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This is a review and detailed measurements of the SMSL A100 A100 stereo amplifier. It is on kind loan from a member. I can't find it on sale anywhere but seems to have cost US 100.
SMSL A100 Review Stereo Amplifier.jpg

I like the simply but rather elegant/symmetrical design. Same for thoughtful rear connections:

SMSL A100 Review back panel subwoofer out Stereo Amplifier.jpg


Almost every manufacturer puts both speaker outputs together making it so hard to plug in the banana plugs. Here they are spaced apart which essentially solved that problem.

Inclusion of an AC power supply is unheard of in this price class and nicely declutters your desk.

Oddly the USB input is type A. At first I thought this was for external storage but manual talks about using this with a computer. I didn't have a type A to type A cable so didn't test this and stuck with Aux analog input.

The heart of the unit is Infineon MA12070 class D amplifier.

SMSL A100 Measurements
As usual we start with our dashboard:

SMSL A100 Measurements Stereo Amplifier.png


Distortion is actually better than 90 dB but there is rising level of noise and high order spikes which drag it down to 76 dB. This puts is slightly below average:
Best desktop stereo amplifier review.png


Edit:
Request was made to measure using USB input. I had to use a special breakout box to interface to the unit given its type A connector. Here is the dashboard:
SMSL A100 Measurements Digital USB In Stereo Amplifier.png


As you see, performance is degrade fair bit. My breakout may be causing some clock jitter but then again, if async USB is implemented, this should not be the case.

Noise performance is "OK:"

SMSL A100 Measurements SNR Stereo Amplifier.png


Multitone shows the same problem at high frequencies:

SMSL A100 Measurements Multitone Stereo Amplifier.png


I expected frequency response to have load dependency but thankfully, it did not:
SMSL A100 Measurements Frequency Response  Stereo Amplifier.png


What ringing it has is above audible band which is good.

Crosstalk is very good, beating some home amplifiers:
SMSL A100 Measurements crosstalk Stereo Amplifier.png


Power output is naturally modest:

SMSL A100 Measurements Power 4 ohm Stereo Amplifier.png

SMSL A100 Measurements Peak Power 4 ohm Stereo Amplifier.png


SMSL A100 Measurements Power 8 ohm Stereo Amplifier.png


Sensitivity to high frequency input becomes very clear as we do power sweeps:
SMSL A100 Measurements Frequency vs Distortion vs Power 4 ohm Stereo Amplifier.png


Unit didn't need any warm up.

Conclusions
The message here is a sum of good and not so good. I really like the frequency response for a class D amplifier and inclusion of AC power supply. Distortion on the other hand rises with frequency. I like to see perfection but we don't have such an example below $350 currently. Overall I would say not a bad attempt. Strange that despite having become available late last year, it is discontinued already. Maybe there are part shortages.

I am going to recommend the SMSL A100 as a budget amplifier.

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

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Last edited:

JSmith

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This is one of the most surprising things I've ever read on this forum.
All I can think is you must have a much lower bar for something to be most surprising than I do... I've read a lot of most surprising comments on this forum and that doesn't even come close to qualifying for me, ymmv. :p


JSmith
 

peanuts

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to bad its discontinued. nice design and integrated powersupply.
 

DSJR

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Going back as far as I do in and around this industry, can any experts here please explain or better *show me graphically* what the old 'crossover distortion' looks like on a APP style of display? Little amps like this look to have huge distortion at high frequencies, but by the standards of yesteryear it's pretty good and only shows up badly here as the rest lower down is so good I think.

I've found a repository online for old audio mags including scans of many UK-important HiFi News issues from the 70's. Crossover distortion was a big thing back then in the days of less well matched transistors and IMD used to be pretty dire on many lower cost far eastern amps I recall. The all important 'tribal spec' then was THD which I suspect could be massaged in the midrange for good figures, as this is all the lay buyer really looked at I remember.
 

DSJR

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This is a class D amp so there is no notion of crossover distortion.
I appreciate that, but my question was what it might *look like* on an AP style display and at roughly what level and frequency spread might it be. Apologies if I have my knickers in a twist here.
 

fricccolodics

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I'm surprised there's any difference at all from the Loxjie A30, though I guess there you could test with digital input.


This is one of the most surprising things I've ever read on this forum.
someone send @amirm a suitable cable? ;) i see they are on offer for as little as 1.99 € over here, let's start a fundraiser!
 

fricccolodics

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This is a class D amp so there is no notion of crossover distortion.
Isn't this is a contradiction to what Benchmark describe on their website:

"Most class-D (switching amplifiers) also use push-pull output devices. The push-pull devices in these switching amplifiers make abrupt transitions between full-on and full-off states. These switching transients occur at a high repetition rate and generally contribute to an overall increase in distortion and noise."
(https://benchmarkmedia.com/blogs/application_notes/131424519-amplifier-crossover-distortion)

Just wondering
 

Saponetto

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Another little amp suitable for office use.
It's a pity it is discontinued, it could represent a "peace of senses thing" for many office colleagues.
 

dominikz

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Thanks for the review!
I expected frequency response to have load dependency but thankfully, it did not:
SMSL A100 Measurements Frequency Response  Stereo Amplifier.png
In case anyone is interested, based on the above measurement I calculate the SMSL A100 output impedance @1kHz around 0,087 Ohms, so damping factor (DF) with 8 Ohm load would be approximately 92.
An amplifier's output impedance often rises at high frequencies, here at @20kHz it appears to be approx. 0,105 Ohm / DF=76.

Of course, the figures may be slightly off as they're based on reading a (digitized) plot and the assumption that the two test loads were exactly 4 and 8 ohms.
 

AR86

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Having spoken to a couple of EU SMSL retailers (inc. audiophonics.fr) they are expecting a restock in roughly 2 weeks, so my guess is that the current lack of available stock is down parts shortages, unless we have a concrete source for it being discontinued?
 
D

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Isn't this is a contradiction to what Benchmark describe on their website:

"Most class-D (switching amplifiers) also use push-pull output devices. The push-pull devices in these switching amplifiers make abrupt transitions between full-on and full-off states. These switching transients occur at a high repetition rate and generally contribute to an overall increase in distortion and noise."
(https://benchmarkmedia.com/blogs/application_notes/131424519-amplifier-crossover-distortion)

Just wondering

In class-d amplifiers we are not talking about an analog output stage. They use transistor switching, that is one transistor pulls hard to the positive rail and the other pulls hard to the negative rail. If both ever came on at the same time the chip would self destruct. The output is developed by changing the width of the resulting chain of pulses, not their amplitude. When you filter it through a low pass filter to block the high speed pulses, you are left with the audio output signal.

Since the output voltage is an analog of a linear change in pulse width if square waves, the class B notion of a crossover notch simply does not apply here.
 

juliangst

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Why is this amp discontinued tho? I've seen this amp being around for like 1 month and then it's already gone
 

mctron

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This was in the $80's a few weeks ago on Amazon. Looked promising with DAC/built in PSU for the price but clearly has some issues.
 
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