SMSL D-6s Balanced DAC Review

[Feesh]

I just tried sample-rate changes via Toslink.
Setup was: RWE (ASIO) @800Hz, -80dBFS -> RME Fireface UC -> Toslink -> SMSL d-6s
I did observe sometimes clicks when changing the sample rate in REW. They were about as loud as the sinewave @ -80dBFS and the amplifier was cranked up to max.
No "pops" however. The D-6s displayed the new samplerate immediately without displaying "---" in between.

Sometimes the D-6s did not recognize the 44.1kS/s (and more rare the multiples of 44.1); sounds distorted then. 48kS/s and multiples were always fine. Still no "pops".

Tried the D6-s with a (slightly) different amp - the SMSL AO200 MKII.

Still had a click/pop which was even a bit louder (the noise floor was noticeably higher on the MKII than my original version).

I guess I will have to try something like the SMSL DO100 or DO300. Hope that's a better match with no clicking/popping.

 

[UA8890]

Tried the D6-s with a (slightly) different amp - the SMSL AO200 MKII.

Still had a click/pop which was even a bit louder (the noise floor was noticeably higher on the MKII than my original version).

I guess I will have to try something like the SMSL DO100 or DO300. Hope that's a better match with no clicking/popping.

I have Topping and Smsl DACs. There are no pops or clicks on the Topping. There are pops and clicks on the Smsl DACs. On some amplifiers. Why is that? Write to the engineers, as I wrote. It should not be.

 

[nanook]

@Feesh: You wrote in #568, that you get these "pops" at the moment when the D-6s displays "---", right?
When I made my tests with the RME- Fireface UC, the D-6s did not display "---" when changing the sample rate.

There are pops and clicks on the Smsl DACs. On some amplifiers.

"On some amplifiers": It might be that the D-6s mutes the output when it displays "---". The output resistance of the D-6s could be different in the muted vs. the active state.
As I pointed out earlier, it is unlikely but possible that the input of the amplifier is DC-coupled and that the input either has some DC-offset voltage or some bias-current. In both cases a change of the source resistance (e.g. due to muting of the source) would become an input signal to the amplifier and become audible.

I can try to check the output resistance on my D-6s.

 

[Feesh]

@Feesh: You wrote in #568, that you get these "pops" at the moment when the D-6s displays "---", right?
When I made my tests with the RME- Fireface UC, the D-6s did not display "---" when changing the sample rate.

"On some amplifiers": It might be that the D-6s mutes the output when it displays "---". The output resistance of the D-6s could be different in the muted vs. the active state.
As I pointed out earlier, it is unlikely but possible that the input of the amplifier is DC-coupled and that the input either has some DC-offset voltage or some bias-current. In both cases a change of the source resistance (e.g. due to muting of the source) would become an input signal to the amplifier and become audible.

I can try to check the output resistance on my D-6s.

Yes, the pop exclusively happens when the DAC displays ''---''.

While streaming Tidal from my desktop PC over USB, I mostly get sample rate changes without the ''---'', which means the ''pop'' happens less often, but it's still there.

Any streamer I tried via toslink has the ''---'' appear on basically every sample rate change with a small ''pop''.

I might try another SMSL DAC like the do100/do300, to see if the same type of problem is present.

I guess the next question would be why the ''---'' appears and how to get sample rate changes without the ''no signal'' step in-between...

 

[danielpugh]

spent some time trying to get clicks. not getting anything currently.
my source was roon, i tried using output of the default device and also wasapi direct to the device.
mulltiple files tried including old mp3 through flac, 24-bit/192, some mqa, and a range of music.
setup: windows 11 -> usb -> wiim amp -> rca to quad s2 + sub out to svs 3000 mini

key things that may be related .
1. windows detected the devices slightly differently depending on the usb port used on the rear of the motherboard (am using blue usb-a).
2. i am using the xmos driver download (i.e. not the default windows driver)
3. i have enabled "always on" on the driver to remove the delay when playing starts. I think this effectively blocks the device from usb sleep
https://www.audiosciencereview.com/...os-driver-settings-for-no-cutoff-delay.25838/
4. i am using a longer cable - i made sure it was usb3.1 capable.

 

[Feesh]

Here are all of my tests summed up. All the testing was done with the amp at 70% volume, playback paused and just switching songs back and forth without playing the actual song.

Tidal Android app

WIIM Mini (coax/optical)> D6-s (xlr/rca)> AO200 - Loud pops when switching bit rates

WIIM Pro (coax/optical)> D6-s (xlr/rca)> AO200 - Loud pops when switching bit rates

WIIM Pro (coax/optical)> 2ndD6-s (xlr/rca)> AO200 - Loud pops when switching bit rates

WIIM Pro (coax/optical)> D6-s (xlr/rca)> AO200mkII - Loud pops when switching bit rates

WIIM Pro (coax/optical)> 2ndD6-s (xlr/rca)> AO200mkII - Loud pops when switching bit rates

WIIM Pro (coax/optical)> DO300 (xlr/rca)> AO200 - Loud pops only when switching to a lower bit rate (192khz>96khz > 44.1khz), the reverse switch (lower to higher) has 0 pops.

WIIM Pro (coax/optical)> Sanskrit 10th MKII (rca)> AO200 - NO POPS whatsoever

Tidal Desktop app

Desktop PC (USB)> DO300 (xlr/rca)> AO200 - No pops - This doesn't really solve my issue since I exclusively stream through coax/optical.


I am feeling a bit lost as to what should be the next step, I really want a slight DAC upgrade so I can use my old Sanskrit 10th MKII on another system.

Is it possible I am missing something? Should I try another model like the DO100 hoping the stars align?

Thanks for all the input!

 

[PyramidElectric]

The DO100 makes little popping noises on sample rate changes and audio start/stop (going into my Genelec 8020) I think it's internals are very similar to the D-6s.

 

[nanook]

The DO100 makes little popping noises on sample rate changes and audio start/stop (going into my Genelec 8020) I think it's internals are very similar to the D-6s.

The D-6s looks like a DO100 just with 1x ES9039 instead of 2x ES9038; I would guess software and muting scheme are comparable.
-- >Is this popping noise also related to the DO100 showing "---" on its display?

The Genelec 8020 seems to have no larger caps in its input section (see PCB photo in https://www.audiosciencereview.com/forum/index.php?threads/genelec-8020b-repair.32876/), so this could mean the 1st stage behind the XLR might be DC-coupled. In case the input stage of the Genelec 8020 is indeed DC-coupled this could be a vague hint to my (admitted - very speculative) suspect that the amplifier might be involved.

@Feesh:
- Do you get a pop when you use the "mute" button on the remote control?
I can hear a very faint click (amp fully open) when I activate the muting as well as when changing the signal source with the remote control

- Can you improvise an adapter with which you can connect headphones to the RCA or XLR output?
If the "pop" still is audible the amplifier is out of suspect.

In order to sort out (or confirm) the amplifier is involved, you could check if there is a "pop" when you compare "input open" vs. "input shorted". If the amplifier has a DC-coupled input with some DC-offset or bias-current, there will be a "pop" too.
!!! But please take great care if you try this. If you touch the inner conductor of the RCA plug while not maintaining a proper connection to the outer conductor, there might be a very loud hum, eventually damaging the speaker or your ears if you closely listen to the woofer if you turn up the volume very high !!!

Edit: replaced D-6s with DO100 in first paragraph

 

[Human Bass]

Mine arrived and it is working perfectly. Super neat and compact

 

[Toku]

Mine arrived and it is working perfectly. Super neat and compact

What kind of device is the audio output of your D-6s connected to? Please tell me the specific device name and connection terminal. . This will be very helpful in pursuing the cause of D-6s.

 

[Human Bass]

What kind of device is the audio output of your D-6s connected to? Please tell me the specific device name and connection terminal. . This will be very helpful in pursuing the cause of D-6s.

Im using my LG TV via optical, that some dacs can struggle with stuttering due to excessive jitter rejection and no problems. Also cellphone Bluetooth working fine

 

[Toku]

Im using my LG TV via optical, that some dacs can struggle with stuttering due to excessive jitter rejection and no problems. Also cellphone Bluetooth working fine

Sorry, my question is regarding the RCA and XLR audio output connections of your D-6s. What kind of device is the audio output connected to? Please tell me the name of the device. It seems that the symptoms that occur with the D-6s differ depending on the device connected.

 

[behindthesofa]

Just to add my observations - hopefully this helps @Toku - I have my D-6s hooked up via RCA to my NAD C268 power amp. I notice subtle pops when the D6s is switching samplerate (and thus is showing --- ). As the pops are soft, I have no issues with them whatsoever.

 

[Toku]

Just to add my observations - hopefully this helps @Toku - I have my D-6s hooked up via RCA to my NAD C268 power amp. I notice subtle pops when the D6s is switching samplerate (and thus is showing --- ). As the pops are soft, I have no issues with them whatsoever.

Thank you for the information.
I started having doubts about the audio output circuits of recent SMSL products from everyone's reports. @nanook seems to have the same doubts as me.
A friend of mine was having trouble with popping noises when connecting his D-6s to SMSL's amplifiers and certain audio manufacturers' amplifiers. However, they have reported that when they connect the D-6s to Topping's PA3s, AIYIMA, and Fosi's amplifier products, no symptoms occur at all. This led me to believe that the problem lies in the audio output coupling circuit method of SMSL products.

 

[Human Bass]

Sorry, my question is regarding the RCA and XLR audio output connections of your D-6s. What kind of device is the audio output connected to? Please tell me the name of the device. It seems that the symptoms that occur with the D-6s differ depending on the device connected.

XLR to my Edifier speakers.

 

[nanook]

In the last few posts there are several hints that the "pops" are related to the interaction of D-6s and the amplifier connected.

The D-6s has no coupling capacitors in the output (just like the application circuit for the ES9039 suggests).
These caps would need to be film caps (electrolytic caps are not well accepted in the audiophile community) and thus large and expensive (and still there would be people that feel that these caps need to be polypropylene and thus even larger and more expensive).

I just measured the output offset voltage and output resistance on my D-6s:

------- RCA output ----------
RCA, left, active: +0.37mV , 101 Ohms
RCA, left, muted: +0.00mV , 110 Ohms
RCA, right, active: +0.32mV , 101 Ohms
RCA, right, muted: +0.00mV , 110 Ohms

The DC output voltage (offset voltage) is fairly small. In the muted state the outputs are connected to Gnd with a similar source resistance.
(I guess they use the SGM3710 muting chip and this chips has either 1 Ohm (active path) or 11 Ohms (muted path), so SMSL should have implemented a 91 Ohm resistor in the muted path and not 100 Ohms like in the active output path).
These ca. 0.36mV should show up on the amplifier output as ca. 7mV assuming an amplifier Gain of 26dB. On my setup this click/pop is audible, but this is an old integrated amplifier with almost 43dB gain with the volume knob fully open.
There is no significant change in the output resistance in the muted state, so even a DC-coupled amplifier (with some input offset voltage or bias-current) should not produce a significant "pop" noise. The turn-on, turn-off and break-before-make times for the SGM3710 are in the order of 100 ... 200ns, so the output of the D-6s will be left "open circuit" for just 100ns (break-before-make-delay).

------- XLR output ----------
XLR, left, "+", active: -0.68mV, 110 Ohms
XLR, left, "-", active: -1.77mV, 110 Ohms
XLR, left, "+", muted: +0.00mV, 21 Ohms
XLR, left, "-", muted: +0.00mV, 21 Ohms

XLR, right, "+", active: -1.26mV, 110 Ohms
XLR, right, "-", active: -1.91mV, 110 Ohms
XLR, right, "+", muted: +0.00mV, 21 Ohms
XLR, right, "-", muted: +0.00mV, 21 Ohms

The DC output voltage is in the order of -1.5mV with the difference for the individual pair being ca. 1mV. This is nothing to worry about, not even when feeding a transformer based input since the source resistance is 200 Ohms and 1mV translates into 5uA assuming the transformer has a DC resistance of 0 Ohms.
The output resistance changes significantly when changing to the muted state. This may produce a DC- step (pop) when connected to a DC coupled input stage with relatively large offset voltage or unequal bias currents, but equipment with XLR inputs usually is AC- coupled.

Looking at the PCB of a Topping E50 you find 4x 100uF electrolytic caps near the output/filter stage. I guess they do AC-couple the XLR outputs and the RCA output is still DC-coupled. Since the RCA output subtracts the XLR "+" and "-", the offset will be fairly small like for the SMSL D-6s.
Edit: Looking at the layout carefully these caps in the Topping E50 are power-supply bypassing.

Remark: The measured value for the output resistance in the active state is influenced by the offset voltage; reversing the input terminals of the DVM and taking the mean value of both readings gives an accurate result.

My personal conclusion:
There's nothing wrong with the implementation of the filter / output stage. The small DC- offset voltage will be easily tolerated in almost any application. Omitting AC-coupling capacitors in the output is a tribute to the audiophile community (cheap caps in the signal path are not welcome) and the ESS application circuit does not suggest capacitors in the outputs either.
I thus have no real clue what's the reason for the audible "pops" that @Feesh observes. Still it would be interesting to see if an "old school" amplifier with AC-coupled input does produce a "pop" too.

 

[Palladium]

Judging from my own SMSL DACs with PC USB mode, those clicks probably occurs from the DAC rapidly entering and exiting soft standby depending on digital input activity.

 

[Glennza]

I've been using the SMSL M8 since it originally came out. Would this be considered a worthwhile upgrade? I'm really only concerned with audio quality, not features. Thanks guys!

Additional: And can it do DSD Direct?

 

[Feesh]

Thanks for all the great information @nanook ! Way out of my league, but a very interesting read nonetheless.

I am in contact with Aoshida support regarding my observations and will hopefully get things sorted.

I am attaching a video of said ''pop'' with the DO300 connected to my AO200.

I would like to note that the sound in the video is practically identical (loudness/type) to all the other combinations using the D-6s and AO200 mkII stated in my previous posts.

Amp was set to 70% volume using the coax input. (USB did not produce any popping sounds).

What is also interesting is that the pop only appears when going to a lower bit rate (96 > 44.1 and seems to be absent when switching from 44.1 - 96). You will also notice 1 transition without a ''pop'', but it happens about 80% of the time.

IMG_8384 (1).MP4

drive.google.com

 

[PhnomPenhPaul]

I've been using the SMSL M8 since it originally came out. Would this be considered a worthwhile upgrade? I'm really only concerned with audio quality, not features. Thanks guys!

Additional: And can it do DSD Direct?

Others familiar with your SMSL M8 may be able to reply to your first query. But as regards your additional question, no the SMSL d-6s will not be able to do DSD Direct since it is ESS Sabre based. [No DAC with ESS Sabre chipset can do DSD Direct].