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SMSL A100 (ma 12070)

cycologist

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Jul 13, 2019
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I listened to the amp and think its an excellent amp for the money.

Pros -
- Small form factor
- Gets uncomfortably loud (Sony Core 5 speakers)
- No hissing, popping
- Excellent detail in music
- Runs cool even when being pushed hard

Cons -
- Internal DAC is so so (didn't test the Bluetooth input just USB)
- No tone controls
- No remote
- Can sound a bit thin / clinical (will listen again after it breaks in, upgrade the power cable)
- The speaker terminals in the back could be better


Overall, I think the amp is an excellent value. Sounds great especially for how small it is!
Had another complementary thought this morning:
Pros: agree, can get uncomfortably loud (Klipsch R41M, whole thing is a tiny office system)
Cons: When first turned on, it mutes itself for a second and defaults back to Bluetooth input rather than what it was set to when turned off. If bluetooth level doesn't match input level of line in source (I had been using a Motu M2 to control the "monitor out" source) you might experience uncomfortably loud.
 

baszek

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Feb 27, 2019
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Can I still buy this amp somewhere ? I can't find it right now even on aliexpress...
 

devoxel

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Mar 15, 2022
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Can I still buy this amp somewhere ? I can't find it right now even on aliexpress...

I can't speak about US but it's available in UK amazon.

I just got one. Its working well, except I can't get AAC or AptX bluetooth working. I tried both with an android phone and a linux laptop. Guess I'll contact the manufacturer
 

dr_mick51

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Mar 12, 2022
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I bought the last one available on Amazon US. But the delivery is on April 15th. There are plenty of SMSL A12, though.
Can anybody point at the differences between both A100 and A12? They use the same chips have BT and SW out, but I like the internal power supply on A100.
Is there a performance difference?
 
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Apr 5, 2020
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I bought the last one available on Amazon US. But the delivery is on April 15th. There are plenty of SMSL A12, though.
Can anybody point at the differences between both A100 and A12? They use the same chips have BT and SW out, but I like the internal power supply on A100.
Is there a performance difference?
The A12 doesn’t have a sub out and the a100 doesn’t have tone controls. I don’t think either have been measured. I’d probably take the A100 if EQ was available because either probably cleaner without tone controls but that’s just a guess.
 

dr_mick51

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Mar 12, 2022
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Guys. I had an early delivery. Instead of April 15th it was delivered yesterday.
So far me experience has been good. After testing it and making sure it works I proceeded to open it:

On the inside we find two boards: one is the power supply which seems of a good quality. It does not show any indication of the OEM, it says SMSL01POWER
IMG_20220321_193618.jpg

IMG_20220322_082251.jpg

IMG_20220322_082201.jpg

IMG_20220322_082151.jpg

It has a MBR30200FCT (30 Amp Schottky Barrier Rectifier 200Volts) and a Lonten LSD65R280HT (Lonten N-channel 650V, 15A, 0.28Ω LonFET TM Power MOSFET)

Now the actual amplifier board:
IMG_20220322_080811.jpg

IMG_20220322_081755.jpg

The main components are:
JL AS218P0A950-2504. I could not find anything about this chip. But it looks like the BT and USB receiver

We also have 2 ST072C opamps, but I traced those down and they don't seems to affect the audio coming from RCA imputs. They might be used 1 for amplifiying the signal coming from the receiver chip, and also used as a low filter for the SW out.
IMG_20220321_192634.jpg


We have a DC-DC step down buck converter for 5V supply and a MAX660 Switched Capacitor Voltage Coverter
IMG_20220321_192853.jpg



Next we have the OPA1678 opamp to feed the Merus MA12720 chip
Gefore the opamp we have the 3710 2007U which seems to be a Relay switch for the multiple inputs (RCA, USB or BT)

IMG_20220321_193059.jpg
IMG_20220321_192730.jpg

IMG_20220321_192816.jpg


The RCA input path is traced to those 2 input capacitors, then go into the relay switch and then to the to pot which is detachable and connect with the ribbon cable. Then it goes to the opamp and continues until it reaches the main chip.
IMG_20220322_081538 redmark.jpg


The case is made of plastic:
IMG_20220322_082843.jpg


The bottom is a metallic plate and it is used as heatsink for the Merus chip by connecting to an aluminum shim or adapter. I removed it and replaced the thermal paste for a better non conductive TIM.

Now, my so far analysis. This is a very nice and small amp. I'm not interested on its USB or BT features (I know they won't be the best ones), I already have a much better DAC for that use. But using the RCA inputs the sound is very good.

Let me tell you about my setup:
I use a computer USB and TV optical into a SMSL SU-6, then it goes into a SMSL SH-6 Headamp/preamp. I also use two Tube Preamps (FX Audio Tube 01 and FX Audio Tube 03 both heavily modified (Tubes, resistors and capacitors on both and opamps on the Tube 03 and fed by a Linear Power Supply). I was using the original black board with nice audio components Aiyima A04, the only mod was to change the opamps to OPA1656 on adapters. That's a good amp, even better than the Aiyima A07. I can confirm that the A04 has more power than the A100, but the sound on the SMSL is better, is more melodic and has more micro details and resolution. It is weird but somehow having three power states compared to two as the usual Class D amps produces a more linear sound, closer to class A, A/B. Even thou the A100 provided up to 5W into 8ohms with 0.005% THD, and up to 11W with 0.01%THD it is more than enough. We don't usually use more than 4-5W on a small room, it gives plenty of volume with speaker the 88 dB/mW and above sensitivity. If I want louder then I use my HIFIMAN HE400SE headphones.

I use a switch for multiple speaker outputs connected to a JVC SX-F50 towers, a Jamo C93 II and a Sony SS-SC5. Additionally I have a Mirage Omni S8 subwoofer which I can now connect directly from the Amplifier instead of one of the Tube preamps using RCA Y cables.
I don't really know how good this amp will measure, but for my ears is a step forward coming from the Aiyima A04. It sounds nice even streaming Amazon Music (not unlimited or HD).

With HiRes files it sounds wonderful. I know I can't compare this to high-end amps but it is enough for me. I might stay like this for a while.
 

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Shimager

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May 13, 2022
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@surfy @Nocturnal-G or anybody who has the SMSL A100 or A12. Can you please post a picture of the inside? I cannot find pictures of those amps. Thanks
Here you go: my SMSL A12 opened up... I was curious too and wondering if we would find the larger coils as also usual with higher power amps. I was expecting smaller coils which I noticed that those usually reduce the bass pressure. Nothing of that all... All small stuff. Amazing that the power can go through such small components. Decent wire on the speaker terminal still. On the back a small metal that shall touch the housing with heat paste. Two holes that should probably have two screws to tighten it with the housing. However those screws are not used. Sound of the A12 is very acceptable although I do miss some bass punch. Otherwise it is not lacking base. The tone buttons are very sensitive; better leave in the middle as it soon sounds offset.
 

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dr_mick51

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Mar 12, 2022
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Here you go: my SMSL A12 opened up... I was curious too and wondering if we would find the larger coils as also usual with higher power amps. I was expecting smaller coils which I noticed that those usually reduce the bass pressure. Nothing of that all... All small stuff. Amazing that the power can go through such small components. Decent wire on the speaker terminal still. On the back a small metal that shall touch the housing with heat paste. Two holes that should probably have two screws to tighten it with the housing. However those screws are not used. Sound of the A12 is very acceptable although I do miss some bass punch. Otherwise it is not lacking base. The tone buttons are very sensitive; better leave in the middle as it soon sounds offset.
Nice, thank you very much. Both amps have a very similar designs:
They share the same chip for USB DAC and BT, this signal is then amplified by the ST072c as in the A100. For the RCA input the amp uses the same 10uF coupling caps. Then both inputs (RCA and USB/BT) go into the same selector switch relay, and the output from the switch goes through the Bass and Treble Opamps which are also ST072c. The A100 uses a better Opamp(OPA1678) before the amp chip than A12, coupled with another set of 4 10uF caps as on the A100 as well.
As you could notice. This amp does not have inductors (coils or SMD chokes) on the output filter. It looks like none of SA300, A100 or A12 (and maybe others Meris amps like the new LoxjieA1) have those choke inductors, therefore the measurements won't look good if the required 4x 10 to 22uH chokes are not used during the measurements.
The Merus MA12070 uses a filterless (inductor-less) design because it can use the speaker coil inductance as an external filter inductor.
But other amps like the Loxjie A30 and the Topping PA3s they do have these tiny chokes and with them, measurements are much better.
You said you are not fully satisfied with the sound coming from A12. I wonder if the ST072c Opamps are at fault. The A100 has 2 of these Opamps but are used for amplifying the signal out of the USB/BT chip (as in the A12) and the other one is used for a low pass filter for the subwoofer outputs. So in the case of RCA inputs, those Opamps are not used at all. But on the A12 no matter which input is used, the signal needs to pass through those 2 Opamps which can degrade the sound.
 
Last edited:

Shimager

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May 13, 2022
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Nice, thank you very much. Both amps have a very similar designs....
Thanks for your additions. Interesting to understand that it uses the speaker inductance. This also would mean that speaker matching is an issue right? Maybe I shall try it with some different speakers to see if it gets the bass impulse pressure which I felt a bit lacking. I would also need some more prolonged listening probably to make final judgements. I did now mainly compare with SMSL SA-98E which did some better impulse pressure... Otherwise I could not place the A100 as I needed the A12 form factor (wider and undeep) and also enabled on 12-30V...
 
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