SMSL A50 Pro Amplifier Review

[DanielT]

We consider this (see below) very poor distortion performance for an amplifier, but fantastic performance for a loudspeaker! This starts to puzzle me more and more: why all this focus on electronics while our loudspeakers show so much more distortion...

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I have, for no logical reason, a rule of thumb that all summed distortion caused by the electronics before the speaker should have at least ten times lower distortion than the speakers have.

That rule of thumb even with vintage amps, receivers is usually achievable (excluding tube amps). In this SMSL A50 case nop.

Speaking of tubes. With SMSL A50 we actually approach the distortion and power levels of what tube amps over half a century old had.

Edit:
Or 0.1% distortion, 15 watts with a nearly century old tube amp design:

Does anyone have a Williamson tube amplifier?

Or have had, listened to a Williamson tube amplifier? Impression? Are they available? What can one, in reasonable condition, cost? I could really imagine having one. Mostly for its HiFi history. :) Not as a main amp but in some nice secondary system. Then together with a subwoofer + LP/HP...

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[peniku8]

Even if it performed well.. what kind of setup do you want to drive with 160W for two speakers and a sub? This is an absolute mystery of a product to me.

Thanks to this member and for your continued testing Amir.

This is a bit of a mess in a number of areas... a shame SMSL can't up the game with their amps, as the feature set is good.

Pics;

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JSmith

Almost looks like just about everything imaginable blew up on this board and somebody replaced all the components by hand. Really odd!

 

[Endibol]

I have, for no logical reason, a rule of thumb that all summed distortion caused by the electronics before the speaker should have at least ten times lower distortion than the speakers have.

That rule of thumb even with vintage amps, receivers is usually achievable (excluding tube amps). In this SMSL case nop.

In that way the loudspeaker is always the determining element in the audio chain. The more reason to put all our efforts in improving loudspeakers

 

[chenubal]

I use a SMSL A50 Pro in by bedroom as a soundbar (two DIY speaker 7"+1") for my TV and as a radio player (Radio Paradise ).
No problems, can't hear noise. Most amplifier with HDMI-ARC are much more expensive.

 

[pma]

Probably similar circuit design like this, with the same issues.

 

[phoenixdogfan]

Well the feature set is everything you could want, but it's terribly underpowered. So much so, noise and distortion numbers are almost irrelevant. Now, SMSL, if you want to give us a unit with this same feature set that can put out 100 wpc into 4 ohms, and have noise and distortion numbers in the mid-80's for digital inputs, AND price it around $200, then you'll have something.

As always, thanks for the great review, Amir.

 

[Kaameelis]

This amp have some kind new D-class modulation, what allows to use output filter without inductors?

 

[Whiskey the Cat]

It is tempting to buy one of these and listen to it for comparison with some of the very high performing electronics that I have on hand. I would learn just how much of a real improvement the better stuff affords.

 

[SuicideSquid]

We consider this (see below) very poor distortion performance for an amplifier, but fantastic performance for a loudspeaker! This starts to puzzle me more and more: why all this focus on electronics while our loudspeakers show so much more distortion...

View attachment 504440

Because it's cumulative, and electronics performance is, in theory, a solved problem, whereas loudspeaker performance is not, so it's worth noting when an amplifier misses the transparency mark by such a wide margin.

 

[solderdude]

hmmm poor measurements, no (recommended) EMC filter with ferrite beads being used (but should be), discontinued power IC being used...

 

[EERecordist]

The subwoofer integration, which costs little, is good feature. But once you add that, it should include a variable crossover point, then the consumer selecting that, usually without a measurement microphone, or auto EQ with a microphone.

I think you may be right that this is a derivative of a soundbar ODM amplifier where distortion is neglected, including from very small drivers in novel geometries to the listening position. The soundbar maker would supply the sub and determine the crossover.

It is cheap!

 

[testp]

hah, i wondered where topping hides all of it's noise..

 

[Endibol]

Because it's cumulative, and electronics performance is, in theory, a solved problem, whereas loudspeaker performance is not, so it's worth noting when an amplifier misses the transparency mark by such a wide margin.

But my point is: f you add all distortion levels of a typical SOTA electronics chain (streamer, DAC, amplifier) then the total is still much lower than that of a top quality speaker.

 

[JohnBooty]

You really have to wonder who this is for. How many people are running passive subs? The number must be minuscule.

I am actually one of those people, maybe -- been meaning to build a Voxel DIY mini sub for ages. So something like this would be ideal if the performance was better. But still... how many of us are there? Dozens?

 

[respice finem]

Maybe it's technical art - title: amp for no reason

 

[JohnBooty]

But my point is: f you add all distortion levels of a typical SOTA electronics chain (streamer, DAC, amplifier) then the total is still much lower than that of a top quality speaker.

Somebody will surely correct me if I'm wrong....

In nearly all cases, the distortion will be cumulative (multiplicative?)

Yes, your speakers will distort the incoming signal from the amplifier. But if that signal is already distorted when it leaves the amplifier, now the distortion is potentially multiplied. A bad photocopy of a bad photocopy, so to speak.

(There are some possible exceptions, like if they're distorting in different parts of the spectrum or something, but that's probably not a typical or realistic scenario?)

 

[JohnBooty]

Maybe it's technical art - title: amp for no reason

Hahaha. Yeah!

As Amir said, it feels like a product created for another purpose. Maybe they got a pallet of the amp boards for next to nothing... somebody else's excess inventory... and figured, well, somebody else paid the development costs... maybe we can make some money on these....

 

[dannut]

The subwoofer integration, which costs little, is good feature. But once you add that, it should include a variable crossover point, then the consumer selecting that, usually without a measurement microphone, or auto EQ with a microphone.

I think you may be right that this is a derivative of a soundbar ODM amplifier where distortion is neglected, including from very small drivers in novel geometries to the listening position. The soundbar maker would supply the sub and determine the crossover.

It is cheap!

These 'soundbar ICs' are a great actually. It is sad that if you want a correctly integrated sub system (delay, variable xo and some kind of trivial 'room correction' - 3 band PEQ) an AVR is still the best solution...

Take e.g. TAS5830, make a nice UI with the above mentioned functionality, package it in a 100-150eur/usd solution and the market is yours. Arylic had something with their ACPWorkbench-compatible devices, but those can be considered borderline-broken in terms of performance.

 

[SuicideSquid]

But my point is: f you add all distortion levels of a typical SOTA electronics chain (streamer, DAC, amplifier) then the total is still much lower than that of a top quality speaker.

The device measured here is far from state of the art.

Speakers and electronics distort in different ways, as well. A good-quality studio monitor is going to have extremely low distortion in the upper-midrange where our ears are most sensitive, but even the best ones will still have (relatively) high distortion in the bass region, whereas electronics typically distort either uniformly across the audible spectrum or in some cases, distortion rises with frequency (many Class D amplifiers), which is generally the opposite of how speakers distort.

Send a 300Hz tone through this SMSL amplifier at decent volumes and you're going to get audible distortion products at 600Hz and 1200Hz, right where our ears are most sensitive.

And again, this is cumulative. It's not like noise where if a source has an -80dB noise floor and an amplifier has a -100dB noise floor, your noise floor is just the higher of the two, -80dB. If you have an amplifier that adds 2% distortion at 10 watts to a speaker that will add another 2% distortion at that volume and frequency, you're going to get more than 2% distortion. [edit] DanielT kindly posted the formula below.

 

[DanielT]

Somebody will surely correct me if I'm wrong....

In nearly all cases, the distortion will be cumulative (multiplicative?)

Yes, your speakers will distort the incoming signal from the amplifier. But if that signal is already distorted when it leaves the amplifier, now the distortion is potentially multiplied. A bad photocopy of a bad photocopy, so to speak.

(There are some possible exceptions, like if they're distorting in different parts of the spectrum or something, but that's probably not a typical or realistic scenario?)

Tip:
For example
0,03% + 0,3% = 0,33%?
Nop...
So this addition is done as follows:
Distortion = SQRT(0.3^2 + 0.03^2) = 0.301%

How do you sum up distortion in the sound chain?

That's the question. Anyone have the answer? It's not as simple as just a plus, is it? For example 0,03% + 0,3% = 0,33%? Edit: After a bit of googling that it seems to be about some kind of Root Mean Square calculation ..Or...

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