Dual Merus MA12070 Amplifier Sabaj A20 fully balanced : pictures inside )

[milan616]

Sabaj's solution is for me to ship the amp to them, which I am hesitant to do because I'd just be paying money to ship them mine and likely get back one with the same problem. I hardly ever listen at -32 on the dial and I haven't come across any other song yet that had the issue. So right now I'm trying to decide if living with it or sending back to Amazon is the way to go. I still have my SA300 ...

 

[ModDIY]

Yes if for you the problem does not cause you any harm, you should keep it.

 

[peterwen]

A20a using the MORNSUN 350w power supply. This power supply makes the amplifier sound better. Compared to the normal 250w power supply A10a used.
In order to comply with environmental protection standards, this power supply has an automatic low power consumption mode, and that relay in the power supply is to control power consumption.When the critical point is triggered, the power supply will automatically switch, and the sound comes from the switched relay.

We are looking for a solution. This machine has an external power interface. Connect the DAC to A20A and there should be no such problem.

You can turn the power amplifier sound louder, and the sound source sound lower to avoid the sound from the relay.

 

[bud947]

@peterwen what do you mean by "This machine has an external power interface. Connect the DAC to A20A and there should be no such problem" ?

 

[Toku]

A20a using the MORNSUN 350w power supply. This power supply makes the amplifier sound better. Compared to the normal 250w power supply A10a used.
In order to comply with environmental protection standards, this power supply has an automatic low power consumption mode, and that relay in the power supply is to control power consumption.When the critical point is triggered, the power supply will automatically switch, and the sound comes from the switched relay.

We are looking for a solution. This machine has an external power interface. Connect the DAC to A20A and there should be no such problem.

You can turn the power amplifier sound louder, and the sound source sound lower to avoid the sound from the relay.

The cause of the abnormal noise was the operating noise of the relay isn't it.

The power supply used for the A20a is MORNSUN's LOF350-20Bxx series 350W power supply, which is the same as the power supply used for the SA400. So the same problem should occur with the SA400 and VMV A2.

On the other hand, the power supply used for DA-9 and AO200 is 225W of LOF225-20Bxx series. Therefore, this problem does not occur in DA-9 and AO200 even though the amplifier configuration is the same as A20a.

The A20a has the same MA12070 chip double configuration as the DA-9 and AO200, but it seems that abnormal noise was caused by adopting a large capacity 350W type depending on the power supply.

However, I don't think this problem can be avoided by adjusting the volume of the A20a.

 

[ModDIY]

Hi,

This is what I wrote above, it is the sound of a relay that is on/off.

 

[Moosi]

Do the two MA12070 instead of one actually improve the sound on lower levels too, or does it just double the power? Would one having an AMP with one chip benefit from going to the A20a if one would only listen on low volumes (Dektop-Levels)?

 

[milan616]

@peterwen what do you mean by "This machine has an external power interface. Connect the DAC to A20A and there should be no such problem" ?

@peterwen do you mean that if we use the A20d and power it via the 15 VDC out port the low power mode of the A20a will be bypassed?

Do the two MA12070 instead of one actually improve the sound on lower levels too, or does it just double the power? Would one having an AMP with one chip benefit from going to the A20a if one would only listen on low volumes (Dektop-Levels)?

It doesn't even double the power (though in theory with a larger power supply it might). The A20a is listed at 90 watts/4 ohms and 50 watts/8 ohms while the A10a is listed at 80 watts/4 ohms and 50 watts/8 ohms (typo from Sabaj? the SA300 and Loxjie A30 say 40w/8ohm). The A20a however should be able to deal a little better with speakers that go below 4 ohm at certain loads, which is not uncommon. It also has sufficiently better SNR (+7 db) and channel separation (+4 db) along with balanced inputs to make better use of the cleaner channels.

 

[bud947]

@milan616 A10a/SA300/A30 power are overestimated. 30w@50ohms and 50w@4ohm are more accurate.
https://archimago.blogspot.com/2020/11/measurements-smsl-sa300-infineon-merus.html

 

[milan616]

@milan616 A10a/SA300/A30 power are overestimated. 30w@50ohms and 50w@4ohm are more accurate.
https://archimago.blogspot.com/2020/11/measurements-smsl-sa300-infineon-merus.html

Oh for sure, but we also don't have any reviews of the A20a or DA-9 max output so I didn't want to compare unlike numbers. Still, that's a great point to include!

 

[milan616]

I decided to try to answer my own question to @peterwen about if using the 15 VDC port would prevent the relay from ticking on and off by using my SMSL SA300 as a load. Short answer: it clicked once and then no longer did for any of my testing!

Longer answer: I knew the SA300 could powered with less than 24v and the barrel plug from the included A20a power bridge cable fit it, so I figured the standby load generated would be a few watts (nothing connected to the SA300 except power). The A10d and A20d use 3.5 watts according to the listing so close enough. I used some burst tones as well as the infamous track @Toku got us started with. Started at -32 with the tones because they're much easier to test with and just as reliable as the song. Got an initial click but never again. I only tried the song to -30 since sitting near field with it is so loud, but the tones were fine down to -24 or so. At -22 one channel seems like it got sent into protection mode on the 35 hz tone so I stopped playing around there. The tones aren't easy loads so I'm not going to read into that too much.

 

[Moosi]

Since the display of my SMSL AS300 broke (went black) and I need to send it in, I am considering the A20a as an alternative. I have no trust in the (O)LED displays SMSL uses for their amps anymore, since mine broke after only 4 month of daily use. I'd rather have a simple one that lasts over a beautiful one that breaks. Power-wise the AS300 is plenty for my Dektop usage tho.

My plan was to use a 108W Mean Well medical PSU to power the AS300. This would be ~50 bucks + another ~20 bucks for the case.

Unfortunately the A20a can't be connected to an external PSU unless you screw it open and connect the plug from the PCB to an external one. The qualities of the internal PSU (Morsun) seem to be in the okayish zone, but none the less inferior to a medical Meanwell.
Since its about rouhgly the same costs, what would you prefer?

a) AS300 +Medical MeanWell 108W PSU
b) A20A +Morsun internal 350W PSU

MeanWell medical:
Earth leakage current < 300uA A/264VAC , Touch leakage current < 100uA/264VAC
Line Regulation Rated load -- ±0.2 -- Load Regulation 0% - 100% load -- ±0.5
Output Ripple & Noise = 24V : 150mV / 48V : 240mV
Morsun:
Leakage Current 240VAC ＜0.1mA; Single fault ＜0.5mA
Line Regulation Rated load -- ±0.5 -- Load Regulation 0% - 100% load -- ±1
Output Ripple & Noise = 24V : 150mV / 48V : 250mV

MeanWell has much better Line&Load-Regulation, in fact twice as good. From using a 108W power with 24V I would benefit from a much lower rippe&noise too compared to a 300W+ high power PSU.
What's better to have? More power or less, but cleaner power?

 

[peterwen]

The cause of the abnormal noise was the operating noise of the relay isn't it.

The power supply used for the A20a is MORNSUN's LOF350-20Bxx series 350W power supply, which is the same as the power supply used for the SA400. So the same problem should occur with the SA400 and VMV A2.

On the other hand, the power supply used for DA-9 and AO200 is 225W of LOF225-20Bxx series. Therefore, this problem does not occur in DA-9 and AO200 even though the amplifier configuration is the same as A20a.

The A20a has the same MA12070 chip double configuration as the DA-9 and AO200, but it seems that abnormal noise was caused by adopting a large capacity 350W type depending on the power supply.

However, I don't think this problem can be avoided by adjusting the volume of the A20a.

Not right,The output voltage of power supply is different, please refer to the data. It's a different product.

I don't know exactly about the power supply of sa400. But it is not the same.

The power supply of A20a contains a relay to control it, once it reaches its high position,it will automatically switch to energy-saving mode. The sound is made by the relay. You can change the sound to pass the peak so that no more sound will be emitted. The relay only has this sound when it works at the moment of conversion. You can try.

We have now requested the power company（monsun） to turn off the energy-saving mode so that no sound will be produced if the relay does not work.

 

[Toku]

Not right,The output voltage of power supply is different, please refer to the data. It's a different product.

I don't know exactly about the power supply of sa400. But it is not the same.

The power supply of A20a contains a relay to control it, once it reaches its high position,it will automatically switch to energy-saving mode. The sound is made by the relay. You can change the sound to pass the peak so that no more sound will be emitted. The relay only has this sound when it works at the moment of conversion. You can try.

We have now requested the power company（monsun） to turn off the energy-saving mode so that no sound will be produced if the relay does not work.

Thank you for the explanation.
Where can I find the explanation about switching the operation of the power supply unit that you say? Please tell me if it is good.
I read the catalogs and data sheets but couldn't find such a description.

The biggest problem with the A20a is that Sabaj has not tested the product for quality.
Such problems can be easily found by performing quality tests before launching the product.

 

[peterwen]

I received a reply from monsun today, and it is possible to stop the relay from working or only work once time that made without this noise, and it can be dealt with soon. Thanks

 

[Moosi]

I received a reply from monsun today, and it is possible to stop the relay from working or only work once time that made without this noise, and it can be dealt with soon. Thanks

a) Will stopping the relay result in a higher standby/idle power consumption?
b) If I want to ensure getting an A20a with the updated relay, at what point in time would I need to order as a European? Since there are no serial numbers printed on the outside of the device, It could be a hassle to seperate the updated ones from the old ones.

 

[Moosi]

It also has sufficiently better SNR (+7 db) and channel separation (+4 db) along with balanced inputs to make better use of the cleaner channels.

If my DAC only has unbalanced (RCA) outs, would I still benefit from using a RCA->XRL cable-adaptor to connect to the A20a?

 

[Zek]

No.

 

[Toku]

If my DAC only has unbalanced (RCA) outs, would I still benefit from using a RCA->XRL cable-adaptor to connect to the A20a?

It's electrically meaningless. You should obediently make an unbalanced connection from RCA to RCA.

 

[Moosi]

So there is a new SMSL AO200, which is technically 100%(???) identical to DA-9, but has the knob in the middle and the display to the side?
https://www.smsl-audio.com/portal/product/detail/id/756.html

Now Im totally confused.