S/PDIF optical out - noise, narrowed down issue, need advice

[CaptainFantastic]

Hello,

I have been using optical out to all of my DACs for a long time. (RME ADI-2, Hugo 2, TT2 with and without M-Scaler).

Quite recently I discovered the following issue. I did a lot of troubleshooting and narrowed down the problem to one aspect. I need help resolving it. I know it can't be RF, not possible with optical.

Optical out #1) Optical out from ASUS ROG Strix Z490-H motherboard (a high quality motherboard, bought brand new last month and installed professionally).

Optical out #2) Optical out from ASUS Essence STX II (via Mini Toslink adaptor as required by this sound card).

#1) Dead quiet I thought. But if I pause either a music track or a Youtube video and I take the volume of the amp to near or at maximum, I hear a hissing noise (somewhat pulsating) for about 10 seconds. The lower impedance the headphone, the higher the hiss, but audible even on 300 ohm Sennheiser. Then it goes pitch black again after 8 to 10 seconds. If after that I lower my volume to normal and restart any audio out (except a Windows system beep, warning sign, etc.) the exact same happens if I pause and take volume to near maximum.

#2) Dead quiet throughout. If I do the same as described above, pause the audio and listen to the amp silence at max volume it is still pitch black on all headphones.

Tests I performed -

a) all my DACs/amps exhibit this for #1.
b) tried switching around three high quality optical cables, same issue with #1, never an issue with #2.
c) updated to latest drivers.
d) disabled all other cards (even the STX) - #1 hiss persists at the near max and max volume (when music paused of course)
e) in Windows quadruple checked that for Realtek Digital Output (this is #1) the following are off: DTS Audio, Dolby Digital, Microsoft WMA Pro Audio, Signal enhancements, audio enhancements, spatial sound. It is set to 2 channel, 16 bit, 44.1k. The two Exclusive mode permissions are allowed.
f) I also made sure in the Realtek app (which I never use), all enhancements/effects are set to off.

The issue persisted. Then I did the following thing:

Qobuz - play a song via Realtek Digital Output - Wasapi -- same issue.
Qobuz - play a song via Realtek Digital Output - Wasapi (Exclusive moed) -- ISSUE GOES AWAY, no hiss at max volume.

So I need help. What is Windows doing in non-exclusive mode that is causing this noise? I disabled all things that could be causing it, but there must be something left. I have the same settings in Windows for #2 and it doesn't exhibit the noise, exclusive or not - except that goes through the STX sound card.

Any help would be much appreciated because I want to use both of my optical outputs.

Thanks!

 

[PurpleAngel]

If you remove the STX II card, do you still get noise thru the Realtek's optical?
If you disable the on-board audio (Realtek), in the BIOS, will you still get hiss thru the STX II's optical port?

 

[technobear]

TLDR: what you are doing is stupid and you should stop doing it and stop worrying about it.

The more technical explanation is that the ROG Strix is outputting very low level dithered noise to keep the DAC awake in between tracks so that you don't get the possibility of switching on noise when the next track starts. This noise is not present during music and cannot be heard even at concert listening levels between tracks. It can only be heard when you apply an absurdly high level of gain way beyond what is normally required to reach full listening volume which is what you are doing here. Stop doing it. You are worrying about nothing here.

 

[CaptainFantastic]

TLDR: what you are doing is stupid and you should stop doing it and stop worrying about it.

The more technical explanation is that the ROG Strix is outputting very low level dithered noise to keep the DAC awake in between tracks so that you don't get the possibility of switching on noise when the next track starts. This noise is not present during music and cannot be heard even at concert listening levels between tracks. It can only be heard when you apply an absurdly high level of gain way beyond what is normally required to reach full listening volume which is what you are doing here. Stop doing it. You are worrying about nothing here.

Wow, I would have never guessed this to be the reason. Thanks.

 

[CaptainFantastic]

If you remove the STX II card, do you still get noise thru the Realtek's optical?
If you disable the on-board audio (Realtek), in the BIOS, will you still get hiss thru the STX II's optical port?

The STX II optical port never exhibits any noise. But I will try at some point removing the STX II to see if the on-board noise persists, although now with Technobear's response it might be a while before I try it. I am going to go ahead and assume he knows what he's talking about, because it's good news.

 

[PurpleAngel]

TLDR: what you are doing is stupid and you should stop doing it and stop worrying about it.

The more technical explanation is that the ROG Strix is outputting very low level dithered noise to keep the DAC awake in between tracks so that you don't get the possibility of switching on noise when the next track starts. This noise is not present during music and cannot be heard even at concert listening levels between tracks. It can only be heard when you apply an absurdly high level of gain way beyond what is normally required to reach full listening volume which is what you are doing here. Stop doing it. You are worrying about nothing here.

Cool, I've learned something new today

 

[Somatic]

TLDR: what you are doing is stupid and you should stop doing it and stop worrying about it.

The more technical explanation is that the ROG Strix is outputting very low level dithered noise to keep the DAC awake in between tracks so that you don't get the possibility of switching on noise when the next track starts. This noise is not present during music and cannot be heard even at concert listening levels between tracks. It can only be heard when you apply an absurdly high level of gain way beyond what is normally required to reach full listening volume which is what you are doing here. Stop doing it. You are worrying about nothing here.

I wouldn’t call it stupid. Using AMP mode in low gain mode with AHB2 at -20 L I can hear this noise. I will test it out today and see if the same noise I’m getting is from Optical. If so, I wouldn’t consider this minor as someone who spent significantly on their system wants zero noise.

 

[Somatic]

Hello,

I have been using optical out to all of my DACs for a long time. (RME ADI-2, Hugo 2, TT2 with and without M-Scaler).

Quite recently I discovered the following issue. I did a lot of troubleshooting and narrowed down the problem to one aspect. I need help resolving it. I know it can't be RF, not possible with optical.

Optical out #1) Optical out from ASUS ROG Strix Z490-H motherboard (a high quality motherboard, bought brand new last month and installed professionally).

Optical out #2) Optical out from ASUS Essence STX II (via Mini Toslink adaptor as required by this sound card).

#1) Dead quiet I thought. But if I pause either a music track or a Youtube video and I take the volume of the amp to near or at maximum, I hear a hissing noise (somewhat pulsating) for about 10 seconds. The lower impedance the headphone, the higher the hiss, but audible even on 300 ohm Sennheiser. Then it goes pitch black again after 8 to 10 seconds. If after that I lower my volume to normal and restart any audio out (except a Windows system beep, warning sign, etc.) the exact same happens if I pause and take volume to near maximum.

#2) Dead quiet throughout. If I do the same as described above, pause the audio and listen to the amp silence at max volume it is still pitch black on all headphones.

Tests I performed -

a) all my DACs/amps exhibit this for #1.
b) tried switching around three high quality optical cables, same issue with #1, never an issue with #2.
c) updated to latest drivers.
d) disabled all other cards (even the STX) - #1 hiss persists at the near max and max volume (when music paused of course)
e) in Windows quadruple checked that for Realtek Digital Output (this is #1) the following are off: DTS Audio, Dolby Digital, Microsoft WMA Pro Audio, Signal enhancements, audio enhancements, spatial sound. It is set to 2 channel, 16 bit, 44.1k. The two Exclusive mode permissions are allowed.
f) I also made sure in the Realtek app (which I never use), all enhancements/effects are set to off.

The issue persisted. Then I did the following thing:

Qobuz - play a song via Realtek Digital Output - Wasapi -- same issue.
Qobuz - play a song via Realtek Digital Output - Wasapi (Exclusive moed) -- ISSUE GOES AWAY, no hiss at max volume.

So I need help. What is Windows doing in non-exclusive mode that is causing this noise? I disabled all things that could be causing it, but there must be something left. I have the same settings in Windows for #2 and it doesn't exhibit the noise, exclusive or not - except that goes through the STX sound card.

Any help would be much appreciated because I want to use both of my optical outputs.

Thanks!

Are you sure you get the hiss/reverb sound in Wasapi mode as well. I believe this is a Direct Sound issue. Anything that uses Direct Sound I have been able to replicate. All other WASAPI etc I have not. Macs and IOS do not have the issue.