SMSL A100 class D amplifier test

[somebodyelse]

You do that often?

It's a commonly described way to do a quick and dirty check for bad RF emissions, especially if you know what frequency range is likely to be a problem.

 

[DoctorRobert]

I got one of these and I am quite happy with it. It was the cheapest tidy solution with an internal power supply and a sub out. I had to use an USB opto isolator to resolve a hum issue coming from my PC. It is used to power a pair of KEF Q100s I already had, and a subwoofer. Equalised with REW the result is quite enjoyable in my small office room. In the appartment building I live in there is so much RF-mess that I doubt that this little amp will affect anything.
As always, YMMV

 

[Bjorn]

Infineon is what Genelec uses if I remember correctly. But different chips.

 

[Sokel]

Infineon is what Genelec uses if I remember correctly. But different chips.

Someone will eat me alive for this,but I think is the car audio variation (which is not a bad thing considering the conditions in a car)

 

[Roland68]

It would be interesting to test an amplifier with a slightly "stronger" Merus MA5332 chip.

This is simple:
SMSL A300 Stereo Amplifier Review
I find the high performance as a mono amplifier in BTL mode particularly interesting.

 

[dr_mick51]

SMSL A100 is sold as a completed product, thus the customer is not supposed to insert inductors or anything into speaker wires. It must work “as is”. The complex load impedance of the speaker is also not pre-defined, parameters are specified to 4 and 8 ohm. I do not understand why some try to protect manufacturers, customers are to be protected.

And I don't disagree with you. I'm with you on this.
Maybe the problem is I don't think as a regular consumer, I'm a hardcore modder.
You are right, regula consumers should be informed and probably don't buy this amplifier under certain conditions.
The Loxjie A30 is a good MA12070 based amplifier and a better alternative.

 

[somebodyelse]

The Loxjie A30 is a good MA12070 based amplifier and a better alternative.

Which also lacks an LC output filter, if I remember the internal pics correctly. There was also a complaint about interference with powerline ethernet in that thread.

 

[SlowJim]

fwiw, i have a RSL ia255 which is also MA12070 and zero interference issues. It sits on my desk between two 4k monitors and a foot away from my mac mini. Also have a macbook pro I use for work and have never experienced any wifi or bluetooth issues.

 

[tmtomh]

The amp's rising distortion above 10kHz is not "unacceptable" unless it produces distortion in the audible band, as determined by something like an IMD test, which results were "better than expected" because "all the junk is above 20kHz."

It's amazing how some folks will avoid putting these two facts together into a single comment, lest other members realize that the amp's HF distortion is not necessarily a problem and not "clearly audible."

 

[Solveit]

MA12070 sounds best with balanced input as Topping Pa3s have, also an filterless amp.
But long speaker cable would pick up noise.

 

[DavidMcRoy]

"However, this brings troubles in the field of electromagnetic interference. My wifi staying near was almost paralysed."

???

 

[amirm]

However, this brings troubles in the field of electromagnetic interference. My wifi staying near was almost paralysed. The DAC feeding the amp with test signals was unable to work without using USB-ISO isolator. For the 5 minute rated power test I had to use analog generator, as the DAC was freezing at amplifier high power due to emitted interference.

You must have issues with your test setup. I am always listening to music while testing including when I reviewed the SMSL A100. Had no interference issues whatsoever. I have had DACs be subject to interference but never had them stop working.

 

[Head_Unit]

troubles in the field of electromagnetic interference. My wifi staying near was almost paralysed.

Ah, if only it was "My WIFE" now THAT might be a feature worth a lot of money!

 

[pma]

Let me return to the EMI issue with this amplifier. The operation of this amp has made Internet 2.4GHz modem/Wi-Fi totally unusable, as I already wrote in this thread. I was prepared to throw the amp to household waste recycling site. But I gave it one more chance finally.

Infeon application note AN_2105_PL88_2105_151947 says this: "The radiated emission test is passed with a margin better than 5 dB over the whole frequency range of 30 MHz to 1 GHz with speaker cables up to 40 cm (see section 3). It is also possible to pass radiated emission with 60 cm cables, though with less margin than
with 40 cm cables."

For cables longer than 60 cm they recommend this:

So I have prepared an additional filter to check the situation

Nothing very nice, but enough to try. I have used my my circular wire probe (placed near the speaker wires) that measures magnetic flux intensity dB/dt and compared results with and without the LC filter.

1. Without the LC filter

Peak-to-Peak induced voltage is 49.5 mV.

2. With the LC filter (33uH, 470nF)

The Peak-to-Peak induced voltage has dropped to 6.34 mV and there is no issue with Wi-Fi anymore. The circular probe is shown just for illustration, dB/dt was measured near the speaker cable.

Conclusion

I do not believe that the SMSL-A100 has passed any EMI radiation test, without additional filters and with cables. To me, any info about this amp passing the test is either misleading or fake.
It is possible to make it working without unwanted radiation, but then it is not a "filterless" amplifier.

 

[Old_School_Brad]

Well, that settles it then. Makes me wonder how many other budget amps have the same issue. There must be people out there spending hours troubleshooting their Wi-Fi and swapping out gear unnecessarily.

 

[thewas]

Well, that settles it then. Makes me wonder how many other budget amps have the same issue. There must be people out there spending hours troubleshooting their Wi-Fi and swapping out gear unnecessarily.

Such issues, plus questionable reliability, serviceability and support make me stay away from such "SINAD wonders" and rather buy devices with lower SINAD (which is still inaudible to me during normal music listening) from decades old and renown large manufacturers.

 

[pma]

Well, that settles it then. Makes me wonder how many other budget amps have the same issue. There must be people out there spending hours troubleshooting their Wi-Fi and swapping out gear unnecessarily.

It is only a case of filter-less class D, ICs like TPA3110 or MA12070. The cheapest junk amplifiers.

 

[Roland68]

It is only a case of filter-less class D, ICs like TPA3110 or MA12070. The cheapest junk amplifiers.

Various inexpensive MA12070 amplifiers (boards) for €/$ 25-50 have filters with coils as standard.
MA12070 PCB
MA12070 AMP

 

[Old_School_Brad]

It is only a case of filter-less class D, ICs like TPA3110 or MA12070. The cheapest junk amplifiers.

Probably -you definitely know way more about this than I do. My point was just that, outside of this very specific niche group we’re in right now, no one would ever notice what would be wrong when their Wi-Fi starts acting up.

Some budget gear clearly comes with its risks, no matter how well it performs otherwise.

Thank you for doing this.

 

[pma]

Some budget gear clearly comes with its risks, no matter how well it performs otherwise.

This one and other similar cheap amps based on TPA3110 (TI) series and MA12070 (Infeon) do nothing right. They are mediocre in all audio parameters. They are just cheap, so you can (or better say could before the start of customs wars) buy them at less than $20 - like this one:

Wondom AA-AB31471 1 x 30 Watt Class D Amplifier Board Review and Measurements

Wondom AA-AB31471 1 x 30 Watt Class D Amplifier Board Review 1. Intro I wanted to have a small audio system for my holiday trip, not to depend on usual TV set sound available at the hotels and pensions. As a speaker I would take my small JBL Control 1 Pro, so there was a question of the...

www.audiosciencereview.com

It has the same issue as the SMSL-A100 - forget about Wi-Fi if it is few meters from the speaker wires.