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SMSL SU-8 Version 2 Balanced DAC

mononoaware

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Hi everyone,

Just thought I should clear some things up.

Noise directly from device (switched on in isolation):
- SMSL SU-8 V2: with ear to DAC constant quiet whine, silent from listening position.
- Apple TV 3 streamer: with ear to ATV, silence.

Noise from ATV -> Optical -> DAC (SU-8 V2) + Monoblocks connected to speakers - all switched on
- XLR outputs: silence from speakers.
- RCA outputs: “coil whine” like sound from speakers, audible from listening position (when nothing is playing, during quiet passages in audio).

Temporary fix: With everything else on, Turn off the ATV. The noise stops.

-

At first since the SU-8 switched on in isolation makes a coil-whine noise (quiet auxiliary sound from device itself), I first assumed this is the same noise coming from the speakers when using the RCA outputs from DAC.

But after further troubleshooting and understanding of the components, it is most likely a ground loop due to the ATV acting like a switch for the noise.

The “coil whine” noise coming from the speakers sounded that way because the speakers used single Fostex FE103NV drivers which when given a pure/un-colored signal produce little to no low-frequencies. This is what must have taken away the typical low-frequency “hum & buzz” associated with ground loop noise, making it sound more like a high pitched whine through the speakers.

Plugged all other components into the same power board into a single wall socket and there is still noise.
Then tried plugging only the ATV to every single other Wall power socket in the room and there is still noise.

So current conclusion is still:
Only use the SMSL SU-8 V2 for its XLR outputs.

A better description of the noise coming through the speakers is like the “ringing” you hear after an extremely loud noise.
It is audible from listening position as soon as the ATV is switched on (playing AirPlay wakes it up from standby) and depending on the dynamic range of the audio content. A way I found to check this is by listening to music that fades away slowly at the end.

Currently it seems like the only option to connect to Monoblock RCA inputs is to get a decently built Streamer/DAC/Pre-amp like the Yamaha WXC-50, and connect the RCA pre-outputs to the Monoblock Power Amplifiers.


Update.

After changing the source to the M1 Mac Mini (via USB) and having the Apple TV 3 unplugged, the coil whine noise from speakers in gone.

Then the auxiliary noise (also coil whine like noise) directly from the SU-8 V2 DAC became more obvious and could be audible from listening position.
I only noticed it occasionally before when close to DAC (sometimes it is just silent) but now it is more noticeable.
I remember reading somewhere that the noise is related to the display, so I tried changing the brightness level of SU-8 display.

When noise is present, I go into menu then change brightness 1-4 (+auto display off = 0), after changing display and then time-out (returning to previous display) the noise changes in pitch and volume.

Oddly Brightness level 3 noise is the loudest, level 4 is slightly quieter, level 2 is then quieter than 4, and level 1 is quietest and inaudible from listening position.
I am currently using level 1 since I need to have a power indicator.
 

Daiyama

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I have a question to this very old device. ;)

Does anybody knows, how the 37-step-volume-control is implemented?
Is it completly in the digital domain by reducing bit depth?
and therefore not really recomended, when not internally upsampled to 32 bit.
or is there some kind of analog pre amp intergrateted? (I doubt this, because of remote control)

Or the other way around: Would recommend to use the SU-8 as a preamp, for example in combination with a fixed power amplifier and or active speakers?
 

denydog

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I'm using the SU-8 V2 directly into my power amp. Controlling the volume via the hand held remote is cumbersome, but it does work. It sounds fine.

The problem is the implementation. The remote is cheap, and I often have to press the buttons multiple times to get it to register. When changing the volume up or down one level, it sometimes skips a level or two. It's kind of cheap and crude. Also the volume steps are a bit large for fine adjustment. Add to that; The numbers on the DAC display are small and hard to read from my listening chair.

All that said, I do like the direct path eliminating the pre-amp, but my pre-amp's volume control set up is far more user friendly.
 

Celty

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I'm using the SU-8 V2 directly into my power amp. Controlling the volume via the hand held remote is cumbersome, but it does work. It sounds fine.

The problem is the implementation. The remote is cheap, and I often have to press the buttons multiple times to get it to register. When changing the volume up or down one level, it sometimes skips a level or two. It's kind of cheap and crude. Also the volume steps are a bit large for fine adjustment. Add to that; The numbers on the DAC display are small and hard to read from my listening chair.

All that said, I do like the direct path eliminating the pre-amp, but my pre-amp's volume control set up is far more user friendly.
I have the same DAC, though not with the remote issues you experience. Nevertheless, I prefer to keep the DAC on full volume and control volume with the amplifier. Works great for me.
 

Daiyama

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Thanks for your comments.
Does anybody can measure that the audio quality is not reduced when using the volume control of the DAC.
I know a lot of people prefer to keep the volume at max but is this really justified or is it only a habit from "old days" aka 16/44 bit DACs.
 

denydog

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I think I remember reading that the volume control on this DAC is a built in function of the ESS dac chip, and is of good quality.
I can't prove it though.
 

JRG123

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Thanks for your comments.
Does anybody can measure that the audio quality is not reduced when using the volume control of the DAC.
I know a lot of people prefer to keep the volume at max but is this really justified or is it only a habit from "old days" aka 16/44 bit DACs.
99% of my music library is 16/44.1. I use the volume control on the SU-8 because A) What's the point of having a DAC with remote control if you're not able to manipulate the volume with it B) My ears cannot detect any lost in the sound quality when I go below the 0dbs ('max' volume on the DAC, 38) and C) I simply don't want to lose my hearing. This is more important to me than losing a handful of bits in the audio stream
 

mononoaware

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Thanks for your comments.
Does anybody can measure that the audio quality is not reduced when using the volume control of the DAC.
I know a lot of people prefer to keep the volume at max but is this really justified or is it only a habit from "old days" aka 16/44 bit DACs.

I have been using SMSL “SU-8 V2” DAC in main system, and Sabaj DA3 Desktop DAC connected with PC.
With both I regularly listen with DAC volume at or slightly below 50%.
It is not because I am completely ignorant, it is because I cannot notice any audible degradation to audio with 50% DAC volume (even listening to DA3 with headphones).

One thing I must mention is SU-8 V2 has a habit of making “popping” sound (output voltage spike) in signal when certain function is adjusted.
Functions which cause this are: 1.initial USB input clock sync, 2.changing sample rate, 3.muting/unmuting, 4.changing “filter/sound color”.

I avoid 1 & 2 by keeping DAC always powered on (I think SMSL claims power consumption: 1 watt) and using fixed sample rate.
I do not use mute or change filter/sound color.

Output Voltage spike was confirmed by Russian person on YouTube using multimeter, it is present on both XLR and RCA outputs.
Russian person used expensive powerful Monoblock amplifier which caused a low frequency “thump” instead of “pop”, so he stated he is concerned about potential damage and will send SU-8 V2 back and purchase another DAC.

In my experience with active studio monitors this “pop” is very quiet, I have no issue or concern with it, but when connected to Monoblock power amplifier it is more noticeable, and therefore I make sure to avoid triggering the popping sound.
 
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Oukkidoukki

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Anyone have opinion about the quality of usb input vs optical? Are they equal? I was able to get chromecast audio (connects with optical and its wirelesly hi res capable). Still, when I connect phone via usb sound is somehow superior. Not much, but enough.
 

JRG123

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Anyone have opinion about the quality of usb input vs optical? Are they equal? I was able to get chromecast audio (connects with optical and its wirelesly hi res capable). Still, when I connect phone via usb sound is somehow superior. Not much, but enough.

I am not familiar with Chromecast audio, can you confirm that the device is not applying some type of processing like re.sampling or EQ? Have you tried the optical input using another source maybe a TV or a CD transport (DVD/Bluray)? I don't think there should be any difference between digital inputs on the DAC, I use USB and Coaxial and they're the same

[QUOTE="I connect phone via usb sound is somehow superior[/QUOTE]


I didn't know you can OTG with the SU-8, I must try that someday
 

Oukkidoukki

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Yes you can otg with su 8. Sound is pretty great. I stream gobuz with usb audio player pro so it is bit perfect. 24bit 192khz works fine. Pretty awesome. There is no prosessing , re-sampling, eq etc. In chromecast. Optical input works from tv and there is nothing wrong with it. I just feel sound is tiny bit better with wire to usb input. I remember amirm tested inputs some time ago and usb was superior in some cases. I don’t know.
 

tades

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Hello
Question on this very old DAC
I use Foobar to read my files (Mostly FLAC)
It's possible in foobar to convert FLAC towards Wav or PCM (and thus avoid this job to the DAC)
Would you advise WAV or PCM to ease DAC job's
Thanks
 

Lucagiovanni

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Something we have changed.

In order to prevent my translation errors, I will keep the Chinese that the engineer told here.Thanks.

输出端这三个开关的供电,由原来的5V提高在9V供电而已,其它在无更改。我们再说明一下,他之前测试时是因为他们测试方式都是以0dB频率信号进行测试的,之上一版本机器就后面开关供电的电压幅度不够所以看起来参数会差一点,但上版本的机器以-6dB频率信号进行测试,参数也会是很好的,当时设计人员认为用户正常使用播放歌曲信号,是不会有0dB频率信号那么高的幅值的,而且这个机器是有前级功能。

还有就是一个多余的时钟没用,删了,加了一个备用的保险丝。这些都不会影响参数的。View attachment 18159


The power supply of these three switches at the output is increased by the original 5V to 9V, nothing other have changed.

Because all tested with a 0dB frequency signal. In the previous version of the machine, the voltage of the power supply behind the switch is not enough, so it seems that the parameters will be a little worse. But if tested with a -6dB frequency signal, and the parameters would be very good,too. When we designed SU-8, the designer thought that the normal user would not have the same high amplitude as the 0dB frequency signal, and the machine is pre-AMP.

An extra clock is useless, deleted, and a spare fuse is added.These do not affect the parameters.
can I replace the fuse with the spare fuse? does it simply come out if I pull up? after I had a power surge mine does not turn on
 

AnalogSteph

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Hello
Question on this very old DAC
I use Foobar to read my files (Mostly FLAC)
It's possible in foobar to convert FLAC towards Wav or PCM (and thus avoid this job to the DAC)
Would you advise WAV or PCM to ease DAC job's
No. The DAC has nothing to do with decoding files at all, that's the first stage of Foobar's processing chain. (Decoder --> ReplayGain --> DSP chain --> output format conversion, then samples are passed to the sound API.) FLAC also is explicitly designed to decode with very little computing power in order to conserve battery power on portable players, and any 10-year-old PC will do so at several hundred times realtime (e.g. an i3-2120 - over 800x according to the Decoding Speed Test component using just 1 thread). You can have the SoX resampler DSP active and still see only a fraction of a percent of CPU usage.
 

tades

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Thank you AnalogSteph!
I asked this because in Foobar/preferences/UPNP/Server/Streaming Profiles you have a box for decoding to PCM with 2 choices:
Never or Always
And if you decode the choice between wav and LPCM.
So I was trying to understand if a DAC as SU-8 has a sort of "native" format limiting the number of conversion?

Should I set Decode to PCM on never?
Thanks by advance
 

tades

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Good question !
I'm controlling my remote foobar by FoobarCon from my Phone ( thus I guess over UPNP)

I was streaming untill recently on a ChromeCast Audio in UPNP/DLNA (then optically to my DAC)... So I supposed question was pertinent.
Was It?

But music is now brought to my DAC over Ethernet RJ45 and a Wattson Emerson streamer.
So does this conversion apply ??? I'm now doubting; You're right probably not

Thanks a lot for this remark !
 
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MrOtto

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How do I interpret these (or the original test) measurements charts in terms of quality of the volume control modultation which this DAC offers?
 

MAK1975

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Anyone have opinion about the quality of usb input vs optical? Are they equal? I was able to get chromecast audio (connects with optical and its wirelesly hi res capable). Still, when I connect phone via usb sound is somehow superior. Not much, but enough.
My SU8 V2's USB port has the popping/drop out issues when I switch tracks using Roon player. Others have reported this issue and from what I can find there seems to be no fix as it appears to be a defect with this DAC. It still plays music fine once it gets passed the inital popping/clicking when you switch a track, but it is still annoying. The SU8's coax port is what I use and it is far superior, at least for me. I get no drop outs or pops when switching tracks. It also has higher volume output when volume matched against the USB port. The lower volume output on the USB might be due to the defective port. I'm using the SU8 V2 connected via an ifi Audio Zen Stream which supports output in both coax and USB. I have tried other USB DACs connected and don't have any issues with the popping and clicking noise. At some point I'll probably replace this DAC to eliminate this popping/clicking startup issue. Other than the popping startup issue, the DAC sounds very good. I have the volume set to max, sound to standard, and PCM filter to fast minimum.
 

JRG123

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My SU8 V2's USB port has the popping/drop out issues when I switch tracks using Roon player. Others have reported this issue and from what I can find there seems to be no fix as it appears to be a defect with this DAC. It still plays music fine once it gets passed the inital popping/clicking when you switch a track, but it is still annoying. The SU8's coax port is what I use and it is far superior, at least for me. I get no drop outs or pops when switching tracks. It also has higher volume output when volume matched against the USB port. The lower volume output on the USB might be due to the defective port. I'm using the SU8 V2 connected via an ifi Audio Zen Stream which supports output in both coax and USB. I have tried other USB DACs connected and don't have any issues with the popping and clicking noise. At some point I'll probably replace this DAC to eliminate this popping/clicking startup issue. Other than the popping startup issue, the DAC sounds very good. I have the volume set to max, sound to standard, and PCM filter to fast minimum.
Have you tried using the SU-8's USB port with another source besides the Zen Stream and Roon? Maybe a PC? Does it behave the same? It is well known that the DAC produces this fade transition when changing bettween different sample rate tracks when using USB (I have confirmed it myself) but nothing about clicks and pops. At least I've never experienced that problem

From iFi website:

"The USB ports – both input and output – support the SuperSpeed USB3.0 standard and benefit from iFi’s Active Noise Cancelling technology to remove distortion from the audio signal.
Similarly, the coaxial S/PDIF output incorporates iFi’s iPurifier signal purifying technology."

ANC for USB ports? What is that even mean? Could it be that said implementation is producing the different volume levels between outputs?
 
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