SMSL M500 DAC and HP Amp Review

[Veri]

There is no balanced headphone output on this unit.

Woops, my bad

 

[skipost-it]

What about Power 50 Ohm & Channel Balance graphs?

 

[amirm]

@amirm,

So, may I ask, which would you get over the other - this, or the DX7Pro?? And why?

I am going through that decision making process. Will report which way I go.

 

[amirm]

What about power 50 Ohm & Channel Balnce graphs?

Channel balance is perfect in these products so I decided to not run that test. And 50 Ohm I only measure when a product has XLR headphone output. I can run it if you are curious.

 

[BDWoody]

Glad to see it do so well especially the amplifier, about as good as DX3 low gain? Nice!

It's really weird though, I saw reports of people complaining about anemic XLR output? When it goes to max 6.8V?! Odd.

I suppose the output impedance is 2ohm SE and thus ~4ohm balanced?

I saw the same thing...all I could think of after having had mine for a while is that it's some basic setting error, or broken unit. Connected to my 705p's there was certainly no lack of SPL's... 9-12 out of 40 was usually enough for casual listening for me.

I have really enjoyed mine...the display is nicely informative without being overly busy, and everything has worked flawlessly for me.

I took a bit of a flyer on this one after seeing the clear focus on quality this company has displayed in their recent products, and I hoped their trend of continuing to make subtle and meaningful improvents would continue with this one. It looks like I was right!

I hope they have a good supply on hand...I'm guessing they will have a few orders.

 

[tmtomh]

I was asked about MQA decoding. I found it work excellently, matching what my Roon player was reporting. [...]

The display on M500 showed the correct setting:

Translating for others who don't follow MQA, the backwards compatible in the clear format is 48 kHz. The hidden bits allow the DAC to decode this back up to 192 kHz sampling.

Amir, thanks for this review! I don't mean to go OT or sound pedantic or ungrateful for your efforts, but I think it's important to correct the bolded statement above, about MQA. The hidden bits allow the DAC to decode the signal back up to 96kHz, not 192k.

96k is the maximum sample rate of any MQA file. The 192kHz output is merely a doubling (upsampling) of the 96k "unfolded" signal. When an MQA file is created from a 192kHz PCM original, the MQA encoder first destructively downsamples the 192k source to 96k. Then it folds the samples between 48k and 96k into the "hidden bits." So the final 192k MQA playback does not contain a reconstruction of any original content above the 96k sample rate.

 

[miero]

It is nice that measurements done by SMSL almost matches amirm's measurements...

Source: http://www.smsl-audio.com/productshow.asp?id=157

 

[miero]

However it is still far from a reference ESS implementation:

The ES9038PRO SABRE DAC features ESS’ patented 32-bit HyperStream™ DAC technology with up to 140 dB – industry leading – DNR in mono mode and –122 dB (0.00008%) total harmonic distortion plus noise (THD+N).

Source: http://www.esstech.com/files/7414/5193/1716/ES9038PRO_Product_brief_121715.pdf

 

[armani006]

There is no balanced headphone output on this unit.

I had connected my 50 Ohm Planar Headphones to XLR outputs of M500 using balanced cable, is it bad idea? How much is impedance on pre-amp?

 

[amirm]

Amir, thanks for this review! I don't mean to go OT or sound pedantic or ungrateful for your efforts, but I think it's important to correct the bolded statement above, about MQA. The hidden bits allow the DAC to decode the signal back up to 96kHz, not 192k.

96k is the maximum sample rate of any MQA file. The 192kHz output is merely a doubling (upsampling) of the 96k "unfolded" signal. When an MQA file is created from a 192kHz PCM original, the MQA encoder first destructively downsamples the 192k source to 96k. Then it folds the samples between 48k and 96k into the "hidden bits." So the final 192k MQA playback does not contain a reconstruction of any original content above the 96k sample rate.

I am fully aware of this and chose my words carefully in the review. The original file was at 192 kHz sampling and the decoding therefore remains faithful to that. There is no useful information above 96 kHz to preserve. So simply upsampling to get to the original sample rate is just fine in my book. This is what a perceptual high-res coder needs to do and MQA is doing.

 

[amirm]

I had connected my 50 Ohm Planar Headphones to XLR outputs of M500 using balanced cable, is it bad idea? How much is impedance on pre-amp?

Usually the line out XLR has high output impedance so it will change the response of your headphone and cause so much internal loss that it will impact bass performance good bit. Best to use the 1/4 jack in the front for any headphone use.

 

[amirm]

However it is still far from a reference ESS implementation:

They may be backing out the analyzer noise figure to get those numbers. In contrast, both mine and SMSL are including the analyzer in those figures.

 

[armani006]

Usually the line out XLR has high output impedance so it will change the response of your headphone and cause so much internal loss that it will impact bass performance good bit. Best to use the 1/4 jack in the front for any headphone use.

Ok, I thought about this effect also but was not sure, ok I understand.

 

[franspambot]

Would this little guy function as a high end line amplifier as well? Say by hooking this up to the Benchmark AHB2 and using it to control the volume?

 

[amirm]

Would this little guy function as a high end line amplifier as well? Say by hooking this up to the Benchmark AHB2 and using it to control the volume?

Of course. And its higher output level should be a good thing for AHB2. You are just limited to digital inputs M500 supports.

 

[franspambot]

Thanks. What an age we live in! (Except of course, everything else. But, hi-fi, you are giving me life.)

 

[tmtomh]

I am fully aware of this and chose my words carefully in the review. The original file was at 192 kHz sampling and the decoding therefore remains faithful to that. There is no useful information above 96 kHz to preserve. So simply upsampling to get to the original sample rate is just fine in my book. This is what a perceptual high-res coder needs to do and MQA is doing.

Thanks for your reply. I don't doubt you chose your words carefully, but the question of whether or not there is any useful info above 96k is irrelevant to the question of whether MQA is decoding the original 192k or simply fabricating it. It's the latter, not the former.

 

[LTig]

I am fully aware of this and chose my words carefully in the review. The original file was at 192 kHz sampling and the decoding therefore remains faithful to that. There is no useful information above 96 kHz to preserve. So simply upsampling to get to the original sample rate is just fine in my book. This is what a perceptual high-res coder needs to do and MQA is doing.

With a recording done in 1974 I don't think there is any useful information above 22 kHz in the first place (except if you like tape hiss). MQA just don't makes sense here.

 

[vkvedam]

Thanks for the review @amirm
On the subject of SNR for headphone out, is it worth having another chart for the normal output along with the 50mV for highly sensitive headphones and earphones?

 

[LTig]

Conclusions
SMSL packs just about every desired feature into a DAC and headphone amplifier including MQA decoding with great measured and subjective performance. The only weakness is that its amplifier doesn't blow your ear drums.

This is not a weakness. It ensures that the user may enjoy this unit also tomorrow.