SMSL D-6s Balanced DAC Review

[Bleib]

Hi every one. If I connect the d6s's xlr to L30II's rca, can I get the 129dB Dynamic range?

100% RCA is more than enough

 

[nanook]

And last not least: If you use only one "leg" of the differential output (XLR) distortion figures are a lot worse. I recently posted a screenshot of a 400Hz signal at -100dBFS. This was feeding the XLR-output into the differential input of the oscilloscope. The sinewave still looked very nice at that level.
Unfortunately I have not made screenshots looking at one individual "leg" of the XLR - the sinewave was visibly distorted.

-> The RCA- output as implemented (low noise OpAmp, low resistive feedback network) is the best you can get when feeding into single-ended input (RCA)

 

[Calolo]

Do you think that using one leg of the XLR output would be good enough to connect a subwoofer RCA inputs ?

 

[nanook]

I just did a quick check comparing the RCA output with the individual XLR-"legs" (non-inverting: pin2-pin1 ; inverting: pin3 - pin1).
My audio-interface is not really good, but I can say that for 630Hz, -10dBFS and 33Hz, -10dBFS (volume at D-6s fully open) distortion is < 0.001% limited by the performance of my ADC. For 630Hz the harmonics were at or belo 0.0002% - again very likely limited by my ADC.
--> No problem with using "one leg" of the XLR if that is convenient. Make sure you use pin2 (signal) and pin1 (Gnd) when connecting to an RCA input at the sub.

The chassis and audio-Gnd is connected to protective earth (PE) in the D-6s. You may encounter problems with ground-loops when several components (worst case all of them DAC, Amp, Sub) have their audio-Gnd connected to PE. This usually results in "hum". Connecting all of the unis to the same power stripe should alleviate this.

PS: In this frequency range (sub) for most music you would not notice 1% of low order harmonics anyway

 

[nanook]

Schematic:
The muting is performed by the well known SG3710. This chip seems to have a charge-pump for the internal negative supply such that it can handle +/-11V signal voltage range with just +11V supply.

AVCC generation:
EDIT: AVCC buffer U2 might be supplied by +5V / Gnd. I have to check next time I have the unit open.

I'v updated the schematic:
- The AVCC buffer OpAmp is supplied by +11V / Gnd. (using the +5V is indeed not possible due to input common-mode range of OPA1612A)
- The SGM3710 is supplied by +12V / Gnd. It has an internal charge pump delivering -12V.

 

[trungdtmc]

I'v updated the schematic:
- The AVCC buffer OpAmp is supplied by +11V / Gnd. (using the +5V is indeed not possible due to input common-mode range of OPA1612A)
- The SGM3710 is supplied by +12V / Gnd. It has an internal charge pump delivering -12V.

If I remember correctly, the SMG is supplied with 4.2V power from the IC A6163Y step down

 

[nanook]

I did indeed measure +12.0V and -12.0 at the cap for the neg. charge pump.
With VCC = 4.2V the analog switch would need to handle signals outside its supply range.

I was actually wondering which +12V are used, but haven't traced that down further.
Probably SMSL did not want to connect the charge pump to the clean +11V so they used the ca. 12.2V directly from the SMPS (maybe with a small resistor in series to end up with +12V)?

I'm talking about the SGM3710 (datasheet attached). Nice Muting-switch b.t.w.

 

[staticV3]

Do you think that using one leg of the XLR output would be good enough to connect a subwoofer RCA inputs ?

It would work, but a 10-20dB boost in THD+N is a likely consequence:



Why not use the D-6s' RCA output to connect to your subwoofer?

If it's already connected elsewhere, then you can use an RCA splitter:

 

[nanook]

It would work, but a 10-20dB boost in THD+N is a likely consequence:

Thanks a lot @staticV3, that's confirming my suspect. And these effects were below what I can measure straightforward.
Topping D10B: Looks like AVCC is properly filtered (at least same filter for AVCC and for Vref of the I/V-stage), so only distortion rises
Topping Pre90: That's actually weird. I would not expect this for a preamp, where there's no need to substract substantial DC anywhere.

An RCA- splitter is the safe way to go, I agree.

Your measurements are perfectly clean - this is an Audio-Precision, right?

 

[staticV3]

Thanks a lot @staticV3, that's confirming my suspect. And these effects were below what I can measure straightforward.
Topping D10B: Looks like AVCC is properly filtered (at least same filter for AVCC and for Vref of the I/V-stage), so only distortion rises
Topping Pre90: That's actually weird. I would not expect this for a preamp, where there's no need to substract substantial DC anywhere.

An RCA- splitter is the safe way to go, I agree.

Your measurements are perfectly clean - this is an Audio-Precision, right?

The measurements are @nagster's:

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[Skelethor]

Hi guys,
can someone tell me if this SMSL D-6S dac works in always on mode?
Or does it have auto power on/off based on input current status?
Is it possible to choose one of these options in the menu?

 

[Skelethor]

Hi, I am using the D-6S together with a Sabaj A20h Amp and I'm very pleased with this combo. Can't imagine anything better in this price range. I have also tested the SMSL DL200 and the Topping DX 3 Pro+ and can compare with my Presonus Studio 1810c. Wouldn't say that there are huge differences in soundquality between the mentioned devices. Maybe there are, but I don't hear them... But the D-6S is looking nice and does the job very well, so it stopped me looking for alternatives any further.

For cables I can highly recommend the Sommer Galileo 238. I use them for ages for everything XLR (Microphones, Studio-Monitors, D-6S to A20h). They are very well built and have sturdy Neutrik Plugs, absolutely nothing to complain about.

Hi Hafnix,
Please help me,
Can you tell me if this SMSL D-6S dac works in always on mode?
Or does it have auto power on/off based on input current status?
Is it possible to choose one of these options in the menu?

 

[trungdtmc]

D6s always on and no setting for auto standby

 

[Skelethor]

D6s always on and no setting for auto standby

trungdtmc,​

Thank you so much.

 

[Kane1972]

Does this DAC have a DAC only mode, where the volume knob is bypassed?

I would love to have the RCA’s connected to a headphone amp (in 2.5v DAC only mode - D6s volume know bypassed) and have the XLR’s connected to my powered monitors in pre amp mode so I can use the volume control on the D6s for the monitors. Would this be easy to do?

Thanks

 

[PyramidElectric]

Does this DAC have a DAC only mode, where the volume knob is bypassed?

I would love to have the RCA’s connected to a headphone amp (in 2.5v DAC only mode - D6s volume know bypassed) and have the XLR’s connected to my powered monitors in pre amp mode so I can use the volume control on the D6s for the monitors. Would this be easy to do?

Thanks

It does not, although volume at '99' works exactly the same as a 'bypass' mode, although for your use case this isn't very helpful. I'm struggling to think of any DACs that do this tbh.

 

[PyramidElectric]

My original Topping E30 has a selectable dac/pre mode, though it doesn't have a knob.

The manuals for the SMSL SU-9n and SU-10 shows the user can select either fixed/variable output volume. I'd think that anything "higher" in the product line would also have that, too.

None of these allow fixed output to the RCAs and variable output to the XLRs at the same time. The E30 doesn't even have XLRs.

 

[sejarzo]

None of these allow fixed output to the RCAs and variable output to the XLRs at the same time. The E30 doesn't even have XLRs.

Sorry, I completely misread the previous post. Will delete my previous reply.

 

[nanook]

Almost all of the DACs use the (so called "digital") volume control inside the DAC chip and this is as good as it can be because the internal resolution of the datapath is 32bit.
Adding separate attenuation for XLR and RCA would either mean 2 DAC chips (separate digital volume control, conversion + I/V) or an additional analog volume control.
Both adds cost, so it will rarely be implemented.

 

[trungdtmc]

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