SMSL D-6s Balanced DAC Review

[nanook]

Thanks a lot for confirmation @trungdtmc. So my measurement seems not to be flawed.
On both D-6s that I measured the left channel did show the THD-vs-level hump more pronounced than the right channel. I might just measure my third unit the next days to see if this is consistent across all three units.

I'm wondering why the DO400 (1x ES9039Pro) does not show this. The output of each of the stereo channels of the DO400 is the average of 4 DAC outputs of that 8-channel chip. In case the phenomenon is related to limit cycles in the SD-DACs that occur at this level, these limit-cycles would very likely be somewhat different on the 4 merged channels due to tolerances and noise. Each internal channel only contributes 1/4 of the amplitude, so this could provide ca. 12dB attenuation. compared to the D-6s.
If merging of several channels alleviates this hump, e.g. the SMSL RAW MDA-1 or DO100 Pro (2x ES9039q2m, but likely very similar analog stage) should show this hump at the same digital drive level, but ca. 6dB less pronounced.
I might as well try to dig deeper into the noise floor of the DO400 - perhaps a hump will then also become visible.

Any other "dual ES9039q2m" based DAC would be welcome to be measured.

 

[atothek]

Is there any disadvantage in using the volume feature of the D-6s, for example to go directly into a power amp like using the D-6s as a preamp/DAC-combo?

 

[Esprit]

This is what I do by connecting it to active monitors.
My Bryston is covered in dust.
No disadvantages, on the contrary...

 

[trungdtmc]

Thanks a lot for confirmation @trungdtmc. So my measurement seems not to be flawed.
On both D-6s that I measured the left channel did show the THD-vs-level hump more pronounced than the right channel. I might just measure my third unit the next days to see if this is consistent across all three units.

I'm wondering why the DO400 (1x ES9039Pro) does not show this. The output of each of the stereo channels of the DO400 is the average of 4 DAC outputs of that 8-channel chip. In case the phenomenon is related to limit cycles in the SD-DACs that occur at this level, these limit-cycles would very likely be somewhat different on the 4 merged channels due to tolerances and noise. Each internal channel only contributes 1/4 of the amplitude, so this could provide ca. 12dB attenuation. compared to the D-6s.
If merging of several channels alleviates this hump, e.g. the SMSL RAW MDA-1 or DO100 Pro (2x ES9039q2m, but likely very similar analog stage) should show this hump at the same digital drive level, but ca. 6dB less pronounced.
I might as well try to dig deeper into the noise floor of the DO400 - perhaps a hump will then also become visible.

Any other "dual ES9039q2m" based DAC would be welcome to be measured.

I will try changing the VRdiv Vref and re-measure when I have time to see if it has any effect

 

[nanook]

I will try changing the VRdiv Vref and re-measure when I have time to see if it has any effect

Do you mean the AVCC divider (the resistive voltage divider that makes ca. 3.67V that gets buffered and provides the analog supply voltage AVCC to the output stages)?
These are modified on my units in order to get the AVCC down to the recommended nominal value of 3.30V.

 

[trungdtmc]

Do you mean the AVCC divider (the resistive voltage divider that makes ca. 3.67V that gets buffered and provides the analog supply voltage AVCC to the output stages)?
These are modified on my units in order to get the AVCC down to the recommended nominal value of 3.30V.

No, i mean this VR

 

[nanook]

No, i mean this VR

Ok. got it.
But wouldn't that only adjust the offset at the XLR+/- pins (the RCA is the difference, so it will stay close to 0mV anyway)?

As far as I figured out (see attached pdf) the output stage that SMSL uses is quite straight forward. They do not apply the common-mode "noise" cancellation proposed in one of the datasheets (see attached png) and as a consequence they need an offset adjustment. But to my understanding this should not really have an effect on the DAC chip. Of course adjusting this Vref away from the common-mode voltage of the DAC chip outputs will introduce some DC current into the DAC chip outputs.

Disclaimer: I can't guarantee my schematic extracted from the D-6s is correct, but I'm relatively confident it is correct

 

[trungdtmc]

Ok. got it.
But wouldn't that only adjust the offset at the XLR+/- pins (the RCA is the difference, so it will stay close to 0mV anyway)?

As far as I figured out (see attached pdf) the output stage that SMSL uses is quite straight forward. They do not apply the common-mode "noise" cancellation proposed in one of the datasheets (see attached png) and as a consequence they need an offset adjustment. But to my understanding this should not really have an effect on the DAC chip. Of course adjusting this Vref away from the common-mode voltage of the DAC chip outputs will introduce some DC current into the DAC chip outputs.

Disclaimer: I can't guarantee my schematic extracted from the D-6s is correct, but I'm relatively confident it is correct

yup, i also just thought of that vref because 9038Q2M hump is affected by it.
The only difference between DL200 and D6s in DAC part i noticed is that DL200 has an extra external LDO supplying DVDD

 

[nanook]

yup, i also just thought of that vref because 9038Q2M hump is affected by it.

There was something related to the operating point of the output stage I remember. The DC current introduced into the DAC chip outputs (when adjusting Vref away from AVCC/2) may indeed have an influence on the SD-modulator.

I would really love to see the output stage proposal shown in the ES9039Pro datasheet implemented. It's the smartest topology I've seen so far. It removes the common-mode "noise" present on the individual +/- outputs and it accomplishes the offset adjustment.

 

[petch]

This might be a stupid question, but can I (and should I) connect the XLR to V3 monos and the RCA to a subwoofer?

 

[staticV3]

This might be a stupid question, but can I (and should I) connect the XLR to V3 monos and the RCA to a subwoofer?

Yes, you can.

There are better ways to create a 2.1 setup, but it'll totally work.

 

[petch]

Yes, you can.

There are better ways to create a 2.1 setup, but it'll totally work.

I'm interested in hearing how!

 

[staticV3]

I'm interested in hearing how!

Using the D-6s this way will send identical signals to both the Sub and your main speakers.

Better results can be achieved if you can modify each signal independently, like for example with a miniDSP 2x4 or miniDSP Flex.

 

[petch]

Using the D-6s this way will send identical signals to both the Sub and your main speakers.

Better results can be achieved if you can modify each signal independently, like for example with a miniDSP 2x4 or miniDSP Flex.

So you would get a miniDSP Flex and use that as the DAC instead of SMSL D-6s? My plan was to just use the crossover dial on the back of the sub

 

[nanook]

So you would get a miniDSP Flex and use that as the DAC instead of SMSL D-6s? My plan was to just use the crossover dial on the back of the sub

I think @staticV3 rather meant that with advanced filtering with one of the miniDSP devices you have more flexibility to achieve a good transition between mains and sub.
If you want to run the mains full-range and use the internal filtering of the sub, your proposal to wire the amplifiers for the main speakers with XLR and to connect the sub via the RCA jacks sounds very reasonable. The outputs of the D-6s are both active all the time, so this is a straightforward way to connect both.

 

[petch]

I think @staticV3 rather meant that with advanced filtering with one of the miniDSP devices you have more flexibility to achieve a good transition between mains and sub.
If you want to run the mains full-range and use the internal filtering of the sub, your proposal to wire the amplifiers for the main speakers with XLR and to connect the sub via the RCA jacks sounds very reasonable. The outputs of the D-6s are both active all the time, so this is a straightforward way to connect both.

Ideally I'd like to exclude the low end entirely from the bookshelves and let the sub handle that exclusively - but the price to do that with miniDSP products is as much as an AV receiver which can do the same thing and more, which I struggle to justify!

 

[nanook]

The low frequency roll-off is different depending on if the bookshelves are ported (24dB/octave) or closed (12dB/octave) cabinets, you can use the roll-off of the bookshelves as high-pass filter. If the sub filter is adjustable in frequency and the filter order (24 vs. 12dB/octave) does match, this can work properly.
The drawback of course is a higher distortion due to the bookshelves having hard times when you hear louder. Having a HP-filter well above the LF roll-off of the bookshelves relieves them from this stress.

 

[petch]

The low frequency roll-off is different depending on if the bookshelves are ported (24dB/octave) or closed (12dB/octave) cabinets, you can use the roll-off of the bookshelves as high-pass filter. If the sub filter is adjustable in frequency and the filter order (24 vs. 12dB/octave) does match, this can work properly.
The drawback of course is a higher distortion due to the bookshelves having hard times when you hear louder. Having a HP-filter well above the LF roll-off of the bookshelves relieves them from this stress.

I'm all for it! I just can't find (or rather, I'm not aware of) a reasonably priced solution that will fit on my desktop

 

[nanook]

There are cheaper devices around, yet miniDSP surely is a (the?) well established product line.
E.g.:

the t.racks DSP 4x4 Mini

the t.racks DSP 4x4 Mini, ultrakompakter 4-Kanal DSP, Eingänge: 4x 6,3 mm Klinke symmetrisch, Ausgänge: 4x 6,3 mm Klinke symmetrisch, Programmierung über USB (Windows), Spannungsversorgung: externes Netzteil 12 V DC (plus innen), Gewicht: 0,6 kg,...

www.thomann.de

the t.racks DSP 4x4 Mini Pro

the t.racks DSP 4x4 Mini Pro, ultrakompakter 4-Kanal DSP, Eingänge: 4x XLR symmetrisch, Ausgänge: 4x XLR symmetrisch, Programmierung über USB (Windows), Spannungsversorgung: externes Netzteil 12 V DC (plus innen) / 1,5 A (Netzteil Inklusive), 3x...

www.thomann.de

I have never "played" with such a device, so you should rely on someone else's recommendation.

These units usually include AD and DA conversion and given the price, they will not live up to the performance of a D-6s. Still debatable if the difference in DAC performance is audible..
If you head for such a relatively complex solution (miniDSP, etc), you will have to dig into filter characteristics and measurement techniques and equipment - it surely is not "plug and play" as far as I can estimate.
--> Maybe someone who's gone through the process of properly adding a sub using miniDSP devices can shed some light on the process and effots?

In the end it depends on how happy you are with your system "as is" and how much effort and money you want to spend.

 

[ICIETDIYEUR]

People hi .

Has anyone 'tested' the SMSL DO100 PRO compared to the SMSL D6s ?

Amir has not (yet) reviewed the SMSL DO100 PRO, although they must have excellent results, and I can't find any measures other than those proposed by SMSL regarding this DAC...

My question here is not only 'aimed' at a comparison of measurements because I doubt that we cannot differentiate at this level between these two models but some people 'perceive' differences when listening (subjective, etc, etc,...) and I would like to know their impressions because I am one of those who (despite the precise measurements known and made) are convinced that there are still differences, even if they are (very) subtle.

NB: I am not trying to create a 'subject' of endless controversy but simply to know the impressions that users have perceived

Thank you