Wolf's Measurements of SMSL M400 DAC

[JohnYang1997]

Why is the vertical scale of the graph set to SPL?

Probably didn't bother to change that setting in REW. SPL is default.

 

[misterdog]

@JohnYang1997 so you happened to take measurements yesterday on your APX 500 and posted them 14 minutes after @ChrisUK posted an anonymous 'review' left on Amazon Japan some 4 weeks ago.

 

[misterdog]

Probably didn't bother to change that setting in REW. SPL is default.

So the review plot from the anonymous Amazon Japan user is taken by someone using a £ 20 SPL microphone and some free REW software ?

 

[JohnYang1997]

So the review plot from the anonymous Amazon Japan user is taken by someone using a £ 20 SPL microphone and some free REW software ?

Probably not microphone. A sound card I guess.

 

[JohnYang1997]

@JohnYang1997 so you happened to take measurements yesterday on your APX 500 and posted them 14 minutes after @ChrisUK posted an anonymous 'review' left on Amazon Japan some 4 weeks ago.

I didn't feel the need to explain any of this. But...
This forum has a function to send notification email to you when there's update in the threads you participated in(reply). So basically I was in the lab was going to measure something else(see okto dac8 stereo thread for information). Saw the notification, found it interesting. So I measured it. It takes only a few minutes to measure stuff like this. Trivial stuff. Then I posted and verified the finding essentially.

 

[JohnYang1997]

Yeah. Went back and check the graph. It's measured on TASCAM US-366 audio interface (a sound card essentially).
I looked at this interface back in 2014. Ola englund was using a similar interface for AMT pedal demo. Old times..

 

[Toku]

It seems that this data was measured by connecting the XLR output and RCA output from the M400 to the TASCAM(TEAC) US-366 digital audio interface.
https://tascam.jp/jp/product/us-366/spec

My doubts,
For some reason, the frequency characteristic of the DAC has not been measured so far. I wonder why?

 

[Veri]

It seems that this data was measured by connecting the XLR output and RCA output from the M400 to the TASCAM(TEAC) US-366 digital audio interface.
https://tascam.jp/jp/product/us-366/spec

My doubts,
For some reason, the frequency characteristic of the DAC has not been measured so far. I wonder why?

-JohnYang also verified it on AP analyser
-XLR output shows no sign of problems. Probably, reviewer would assume RCA to show no problems too. But, it seems only RCA shows the 'fault'.

 

[SECA_alan]

I am a layman, please forgive the question: how is it the RCA and the XLR can have a different frequency response?

BTW @WolfX-700 I wanted to thank you for your review earlier, I appreciate your efforts and always enjoy reading them.

 

[Veri]

I am a layman, please forgive the question: how is it the RCA and the XLR can have a different frequency response?

Normally this wouldn't happen! It has to be a mistake in the hardware. Unless the cause is verified, it is hard to say for now but it likely has something to do with the uncommon output stage (with its high output impedance). Perhaps it is random luck XLR does not have it while RCA does, but still they really should have seen the mistake during the product development.

 

[SMSL-Mandy]

Because we already have an XLR interface with very good performance, we hope that the RCA interface is more musical, this is a design based on sound adjustment, and I hope this interface is more analogous! There is no problem! Just like the normal SLOW type of digital filter will also have a great attenuation in the high-frequency range!

If the parameters data need to be better, we only need to change the output capacitance value.

We can provide tutorials and tools, which will be updated later, you can contact the seller to get capacitors and tools for free.

 

[sq225917]

Mandy, so is this roll off just caused by the output coupling caps on the rca line?

 

[JohnYang1997]

Mandy, so is this roll off just caused by the output coupling caps on the rca line?

Not coupling caps. A low pass.

 

[BAMCIS]

It has been a long time since the last time I published the measurement report.

There are many reasons for the disappearance of this period. At the beginning, it was caused by the epidemic and the Chinese New Year. It is difficult for me to receive new equipment for measurement.Everyone knows that the development and production of new equipment has also been affected a lot.

As the impact of the epidemic in China disappears, my family is preparing for the birth of a new baby ... In order to prepare for this, I am busy renovating one of my garages-using it as my measurement studio-this work is not yet complete carry out.

In fact, I have received some equipment since April, but they are all prototypes. In addition to Topping A90, there are areas where I have feedback and the manufacturer said that it will make improvements before the official sale. ----- Again I emphasize that this feedback is free.

Debugging of prototypes and pre-production equipment is my pleasure. After the product fixes the related bugs, it will go on the market again-let the fans get a more complete product. This process will make me very happy.

SMSL M400 is one of the devices that has been improved and sent to me in the official retail version.

Okay, go for it!

View attachment 65936

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In terms of interface, apart from the texture of the connector, there are not many complaints (I wanted to say that AES is missing, but I know there is really no place )

I'm still not satisfied with industrial design and workmanship. One of the simplest improvements: the interface fixing screw on the back should be black! The surface treatment of aluminum alloy, the acrylic on the upper surface, the texture and feel of the front knob ... There are too many places to discuss and improve.

Measurements:

View attachment 65938

Since the output level is relatively high, I lowered the volume to 75 (80Max) to obtain the measurement result (XLR) at 4V level:
View attachment 65947

But what actually impressed me more is the result of RCA:
View attachment 66081



View attachment 65941

View attachment 65939

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View attachment 65944

What volume level was the RCA measurement taken at, 75 or something else? This would be a great standard item to include with the SNR screen shot considering some DACs with volume control reach 4 volts at different places in the volume range than others. If the best SNR is reached at different volume levels that worth knowing, I run the XLR's to my power amp and the RCA's to my subs. I know that's not going to be a big deal for sub SQ if they are optimum at different levels but since we are already here... what do the RCA's measure at the best SNR of the XLR's and vice versa? Apologies if this is already shown and I overlooked it-

 

[ShiZo]

Is the rca fixed in the new m400s?

 

[sq225917]

The differences in snr with volume at the top of the dial is likely due to autoranging on the AP, not the DUT. Follow the trend line instead.

 

[JohnYang1997]

The differences in snr with volume at the top of the dial is likely due to autoranging on the AP, not the DUT. Follow the trend line instead.

It's very normal and expected to have reduction in SNR when reducing the volume. It's when the SNR suddenly drops as the volume increases, the issue of AP's autoranging.

 

[SMSL-Mandy]

All sell now is the new version.

Is the rca fixed in the new m400s?

 

[ShiZo]

All sell now is the new version.

So all the new units have the rca fixed? Trying to clarify.

 

[JohnYang1997]

So all the new units have the rca fixed? Trying to clarify.

Yes and iirc there would be a sticker on the side indicate newer/fixed version.