SMSL RAW-MDA 1 DAC & Headphone Amp Review

[nanook]

The problem of electrostatic charge accumulation and device restarts under their influence is a real problem!

@Burns: You are sure it is electrostatic discharge?
You can check this by discharging yourself before touching the unit; e.g. touch the case or RCA sockets of a different device (or even those of the DAC). Do not move your feet, do not stand up from a chair etc. before you plug in the 3.5mm connector.

There might be another possible cause, which looks more likely to me:
These TRS connectors (3.5mm as well as 6.3mm etc.) tend to make a short- circuit while getting inserted. In case the RAW MDA 1 is using the TPS6120A, this chip is capable of typ. 0.7A output current per channel. The datasheet does not comment on whether the outputs are short- circuit protected, so the current might be even higher.
--> It might be, that when you plug in the 3.5mm connector (causing a short circuit) while there's music playing, the HPA draws a lot of current and the internal supplies are overloaded. The SMPS may in turn shut down and restart. The microcontroller in the unit will in turn reboot.
With the music stopped (or with the line outputs engaged), the DC offset voltage at the output of the HPA will likely be small enough such that the output current remains in a reasonable range. I actually feel a bit uncomfortable plugging and unplugging TRS connectors while there's significant signal present.
This behaviour might even be somewhat different depending on the 6.3mm - 3.5mm adapter used; the likelihood of making a short- circuit may differ.

@flint350 described he was quickly plugging and unplugging the 4.4mm HP connector. I'm not familiar with this connector, but maybe this one does not make transient short- circuits while being plugged / unplugged?

 

[Burns]

@Burns: You are sure it is electrostatic discharge?
You can check this by discharging yourself before touching the unit; e.g. touch the case or RCA sockets of a different device (or even those of the DAC). Do not move your feet, do not stand up from a chair etc. before you plug in the 3.5mm connector.

There might be another possible cause, which looks more likely to me:
These TRS connectors (3.5mm as well as 6.3mm etc.) tend to make a short- circuit while getting inserted. In case the RAW MDA 1 is using the TPS6120A, this chip is capable of typ. 0.7A output current per channel. The datasheet does not comment on whether the outputs are short- circuit protected, so the current might be even higher.
--> It might be, that when you plug in the 3.5mm connector (causing a short circuit) while there's music playing, the HPA draws a lot of current and the internal supplies are overloaded. The SMPS may in turn shut down and restart. The microcontroller in the unit will in turn reboot.
With the music stopped (or with the line outputs engaged), the DC offset voltage at the output of the HPA will likely be small enough such that the output current remains in a reasonable range. I actually feel a bit uncomfortable plugging and unplugging TRS connectors while there's significant signal present.
This behaviour might even be somewhat different depending on the 6.3mm - 3.5mm adapter used; the likelihood of making a short- circuit may differ.

@flint350 described he was quickly plugging and unplugging the 4.4mm HP connector. I'm not familiar with this connector, but maybe this one does not make transient short- circuits while being plugged / unplugged?

it may be as you describe and what should I do now? Why didn't I manage to repeat it on other devices like l50 and dx3pro+ and a stationary Denon receiver. As you can see, all devices, despite the wooden base, are close to the TV. The phenomenon does not occur in the morning when everything was turned off. Only in the evening when MDA1 and TV are turned on for a long time, min. 1-2h. It seems to me that the DAC housing or maybe other circuits of the device collect MDA1 collect charges from the TV, which would make sense when others described their computer stations and mentioned velour armchairs or Alpaca carpet

 

[nanook]

it may be as you describe and what should I do now? Why didn't I manage to repeat it on other devices like l50 and dx3pro+ and a stationary Denon receiver. As you can see, all devices, despite the wooden base, are close to the TV. The phenomenon does not occur in the morning when everything was turned off. Only in the evening when MDA1 and TV are turned on for a long time, min. 1-2h. It seems to me that the DAC housing or maybe other circuits of the device collect MDA1 collect charges from the TV, which would make sense when others described their computer stations and mentioned velour armchairs or Alpaca carpet

Ok. that really sounds like it could be electrostatic discharge.

The RAW MDA 1 has an internal power supply like most of the SMSL gear. For the D-6s e.g. the case is connected to protective earth (PE). If this is the case the unit cannot get charged. Still you - holding the cable - can get charged.
-> Can you measure if the Gnd-terminal of the RCA jacks of the RAW MDA 1 are connected to the PE pin of the mains cable?

Another thing you can check, is, if this happens as well when you stop the music playing before you plug/unplug (to rule out / confirm the short-circuit theory).
The TPA6120A2 seems to be somehow short circuit protected: https://e2e.ti.com/support/audio-group/audio/f/audio-forum/377352/tpa6120a2-short-circuit-protection

 

[Burns]

-> Can you measure if the Gnd-terminal of the RCA jacks of the RAW MDA 1 are connected to the PE pin of the mains cable?

How to do it without opening the device?

Another thing you can check, is, if this happens as well when you stop the music playing before you plug/unplug (to rule out / confirm the short-circuit theory).

It doesn't matter if the music is on. Just select the HP output source and insert anything into the 6.3mm socket. It doesn't matter if I insert the 6.3/3.5mm adapter, the 5m/3.5mm cable, which can be seen in the picture, or the headphones themselves. As I wrote, I did it even in rubber gloves, which should provide insulation? It seems to me that when the 3.5mm plug passes through the socket connectors, it causes a restart. I associate this phenomenon with very old devices from the 90s.

 

[nanook]

How to do it without opening the device?

I meant just measuring if the resistance between the Gnd of the RCA jacks and the PE pin of the mains connector is high or if it is close to 0 Ohms.
-> Do you have a simple multimeter that can measure resistance?

On the SMSL D-6s and the DO400 the internal Gnd of the unit (e.g. RCA jacks) = case = PE pin of the mains inlet. On these units I measure close to 0 Ohms for these connections.

It is very likely, that SMSL did the same for the RAW MDA 1, but maybe someone else can confirm in case you do not have a multimeter.

 

[nanook]

 

[Burns]

I meant just measuring if the resistance between the Gnd of the RCA jacks and the PE pin of the mains connector is high or if it is close to 0 Ohms.
-> Do you have a simple multimeter that can measure resistance?

On the SMSL D-6s and the DO400 the internal Gnd of the unit (e.g. RCA jacks) = case = PE pin of the mains inlet. On these units I measure close to 0 Ohms for these connections.

It is very likely, that SMSL did the same for the RAW MDA 1, but maybe someone else can confirm in case you do not have a multimeter.

I have a meter, tell me where to put it.
Do you have a good enough eye to judge the construction of the device based on the pictures of the integrated circuit board that someone showed in this thread?

 

[Burns]

View attachment 412793

I understand, I'll do it when I get back from work

 

[Burns]

Personally, I don't like what I marked in red in the photo, as you can see it is another layer of the board, maybe this screw if it is a screw that goes into the device housing?

 

[nanook]

From the photos in the video, the power-supply looks just like the one in the D-6s, so it is very likely they connected the PE pin of the mains terminal to the chassis an the internal Gnd.
The screw that you marked looks indeed a bit strange. SMSL usually puts some connectors or rotary encoders (knob) on a breakout board in order to change the vertical position in the front panel. Here the difference in height seems to be very small.
I cannot really believe that the only connection from Gnd (PCB) to the chassis is through this screw and one or several of the neighboring solder joints.

Anyway I would check if the resistance is close to 0 Ohms between
- PE pin of the mains inlet and chassis screws on the rear
- PE pin of the mains inlet and RCA jacks

The meter must be in the Ohms position (range either 200 Ohms or 2000 Ohms depending on the multimeter).

On the DO400 it looks like this:

The screw in the front with the symbol for PE seems the one that contacts the chassis to PE. It's next to the PE connection to the mains inlet, so that looks good.
And I think I see that symbol on the MDA1 as well:

B.t.w., the HP connection breakout board on the DO400 looks like this. So "business as usual".

Anyways, I would check the connections of PE to chassis and internal Gnd (RCA jacks).

 

[nanook]

The MDA1 seems to have a nice discrete HP-Amp. The measurements Armir showed in this review speak for themselves - the circuit seems to outperform the TPS6120a2.

 

[Burns]

The MDA1 seems to have a nice discrete HP-Amp. The measurements Armir showed in this review speak for themselves - the circuit seems to outperform the TPS6120a2.

View attachment 412813

as I said: I'll take measurements with a multimeter in the afternoon (I'll let you know)

Maybe you have another idea what I can measure (voltage?) when the device is turned on, e.g. between the housing and the HP 6.3mm plug?

Since it has such a nice amplifier and measures well and plays nicely, what do you advise, ignore these short circuits and learn to live with it because it's no big deal, or shouldn't it happen and another restart of the device qualifies it for a definite return?
I still have the purchase of the Topping L70amp in the back of my mind because I already have the E70 Dac.

 

[nanook]

Maybe you have another idea what I can measure (voltage?) when the device is turned on, e.g. between the housing and the HP 6.3mm plug?

If there was relevant DC voltage at the output you would notice while plugging / unplugging with the music stopped.

Since it has such a nice amplifier and measures well and plays nicely, what do you advise, ignore these short circuits and learn to live with it because it's no big deal, or shouldn't it happen and another restart of the device qualifies it for a definite return?
I still have the purchase of the Topping L70amp in the back of my mind because I already have the E70 Dac.

Given that both DACs and both HPAs measure just SOTA, I doubt that there's an audible difference between the MDA1 and the Topping combo, unless you have extremely demanding headphones that need a balanced output stage.

The MDA1 has the newer generation DAC chip (Hyperstream IV) and it is an all-in-one solution offering great flexibility regarding its input capabilities.
-> Depends on how much money you want to spend and if "space for two units" is a concern.

Features:
I recently figured out that I do not want to do without equalization. The speakers in my living room clearly have a frequency response issue - yet I want to keep them because the cabinets have been built very nicely by my father almost 20 years ago. I've started to experiment with the room-equalization of the WiiM Pro (so far just a best guess setting based on a frequency response graph - the UMIK 1 should arrive before Christmas to allow for a more accurate correction) and I already don't want to miss this feature anymore. So I try to get all sources (incl. TV) into the single Toslink input of the WiiM Pro. I can stream from my laptop using the foo_out_upnp plugin in Foobar2000, so everything is routed through the PEQ of the WiiM. The SMSL D-6s is connected via coax and serves just as a DAC.
--> Features might make a bigger difference

 

[Burns]

After testing the Topping L50 I don't expect to hear the differences in the L70, I just need an internal power supply and a remote control. I really like the functionality of the RAW-MDA1, I would really like to keep it. I don't look for problems on purpose. It just so happens that I connect the headphones in the evening, when I can no longer listen to large audio. The problem appeared by itself and it is real, not invented.

The RAW MDA1 device, which can be seen in the photo, is already in its final location and not in the testing phase like the others. It really was supposed to stay at my house, but it is ungrateful for the hospitality.

 

[JIW]

it's possible that it's the fault of the song or the mqa being sewn into the song. it's true that some are smooth and some with a skip in about 4s https://tidal.com/track/165535576?u

this maq is not important to me. The problem of electrostatic charge accumulation and device restarts under their influence is a real problem!

No problem on that track for me. It takes maybe half a second to detect MQA and make the switch.

 

[nanook]

The problem appeared by itself and it is real, not invented.

I absolutely believe this and that's really a nasty fault.

In case the fault doesn't show up when plugging / unplugging with the music stopped, you can still decide if this is a way to go. Still this behavior is not the way it should be, so maybe your unit is faulty indeed.

@JIW: Do you experience similar problems (reboot) when plugging /unplugging a 6.3mm jack or a 3.5mm jack?
I cannot test this out, I haven't got the MDA1.

 

[JIW]

I absolutely believe this and that's really a nasty fault.

In case the fault doesn't show up when plugging / unplugging with the music stopped, you can still decide if this is a way to go. Still this behavior is not the way it should be, so maybe your unit is faulty indeed.

@JIW: Do you experience similar problems (reboot) when plugging /unplugging a 6.3mm jack or a 3.5mm jack?
I cannot test this out, I haven't got the MDA1.

I also don't have one. I only have a DL200 with no such issues.

 

[Burns]

SMSL AO300 clicks/resets due to headphones esd while petting cat, wearing socks, etc.

While wearing headphones, I can reliably force a clicking noise, which is caused by the AO300 unit itself seeming to temporarily reset. The sound will cut out and the LCD will display "DoP 2.8224 MHz" for about 1 full second before the unit switches back to the previous output settings and plays...

www.audiosciencereview.com

 

[nanook]

SMSL AO300 clicks/resets due to headphones esd while petting cat, wearing socks, etc.

While wearing headphones, I can reliably force a clicking noise, which is caused by the AO300 unit itself seeming to temporarily reset. The sound will cut out and the LCD will display "DoP 2.8224 MHz" for about 1 full second before the unit switches back to the previous output settings and plays...

www.audiosciencereview.com

That photo indeed looks a bit strange to me. I would expect that a unit like this needs the chassis be connected to PE. The mains inlet seems to be 3-prong, but internally it's not connected and I can't see a screw that is labelled with the PE symbol.

In case you want to keep the MDA1, I'd return it with the fault description and ask to ship a replacement.

 

[Burns]

That photo indeed looks a bit strange to me. I would expect that a unit like this needs the chassis be connected to PE. The mains inlet seems to be 3-prong, but internally it's not connected and I can't see a screw that is labelled with the PE symbol.

In case you want to keep the MDA1, I'd return it with the fault description and ask to ship a replacement.

I ordered a second one, but I don't really believe in a miracle because the reviews on Amazon also mention this problem, there are more posts with similar problems to mine on this forum. This also applies to other devices from this manufacturer, which I linked above. If the same thing happens to the second one, I will definitely part with this device once and for all, maybe also with the SMSL company.