• Registered: 2017-08-30
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Topic: lot of white noise when playing an audio source through the SPDIF

Hello,

I recently purchased the RME ADI-2 Pro. First of all, I did some tests with different setting, in particular in USB mode and in AD/DA mode with the SPDIF (using an U-XMOS192 USB to SPDIF converter).
The previous DAC I used was the RME ADI-2. It was connected to my PC through the USB to SPDIF converter, and I can say that I was totally satisfied with the quality of the sound, the transparency, the degree of definition and precise sound stereophonic image.

Before exposing my problem with the new ADI-2 Pro, I would like to give my general impression about the new product:

Compared to the old ADI-2, the ADI-2 Pro clearly provides more details, particularly in the high frequencies, and a better bass frequency rendition. Both female and male voices are rendered with less arshness and sibilance, however I'm somewhat disappointed to find that voices have sometime such a twangy feeling, as if there was an excess of high frequencies and a lack of low and medium frequencies, especially in USB mode. In USB mode I also notice a significant loss of accuracy in the stereophonic image, the locations of instruments and voices being not well defined.
Finally I get the best result when using the SPDIF input instead of the USB, in AD/DA mode, and with the SRC turned off. 

Let me now come to the specific problem I'm facing with the ADI-2 Pro when using the SPDIF.

Note that the RME ADI-2 Pro is connected to my PC/Windows10 through an USB to SPDIF converter (AUDIOPHONICS U-XMOS192). 

*** I get a lot of white noise when playing an audio source through the SPDIF. ***

- The problem did not occur when using the old ADI-2 (with same PC and same USB/SPDIF converter);
- The problem occurs solely on Outputs 1/2 but not on Phones Out 3/4;
- The problem occurs only when using the SPDF input, not the USB;
- The problem does not occur when using the Windows device driver in the Exclusive mode.
- The level of the noise does not depend on the volume level, but on the sample rate provided by the Windows driver. The noise level is maximum at the highest rate (192 kHz).

Thank you in advance for your support!

Regards

Roland

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Re: lot of white noise when playing an audio source through the SPDIF

What is the firmware version of your ADI-2 Pro?

When you have the white noise effect, what does the State Overview say? And how much 'white noise' is there in level?

Sounds a bit like DSD playback without DSD mode getting active.

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Matthias Carstens
RME

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Re: lot of white noise when playing an audio source through the SPDIF

It's the latest version of firmware.
The level of the noise is quite high. It is as if it depends on the difference between the native signal bitrate of the audio stream and the output bitrate defined in Windows sound panel. It can be of the same order of magnitude as the audio signal when the volume is at a moderate level, let say between -40 or -30 dB.

Before going further, I think I would better set back the ADI-2 Pro to the factory settings, in order to be sure there is no unexpected combination. I will get back to you then.

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Re: lot of white noise when playing an audio source through the SPDIF

I would still like to know what the State Overview says. You can type down the few information in there or take a photo and upload it somewhere.

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Matthias Carstens
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Re: lot of white noise when playing an audio source through the SPDIF

Sorry I'm not at home now. I'll do it this evening.

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Re: lot of white noise when playing an audio source through the SPDIF

Also you should tell us which Basic Operation mode you use - AD/DA (Auto) or DAC.

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Re: lot of white noise when playing an audio source through the SPDIF

The State Overview says that :

Input       Sync     SR           State       Bit
SP co    sync        192     cons        16
AES          --          --        --             --
USB         conn     192      2/2
SRC         off
Clock Source                  SPDIF

The problem is the same in both AD/DA and DAC modes, and with or without SRC.

The noise disapears only if I set the output bitrate in shared mode to the same value as the native bitrate as the source (e.g., 48k for a YouTube video) in the Sound panel of Windows :

Audiphonics U-XMOS192 interface USB/SPDIF
  > Properties
    > advanced
      > select the sample rate and bit depth to be used when running in shared mode
        > 16 bits, 48000 Hz (DVD Quality)

The highest level of noise is obtained with 24 bits, 192000 Hz (Studio Quality)

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Re: lot of white noise when playing an audio source through the SPDIF

Does the problem disappear if you remove the USB cable from the ADI-2 Pro?

I have to ask again for the exact firmware version. It is shown on start in the RME screen: Vxx.

You still have the old ADI-2?

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Matthias Carstens
RME

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Re: lot of white noise when playing an audio source through the SPDIF

I'll be able to remove the cable in the evening once back home.

Firmware Update 144 DSP 81

I still have the old ADI-2

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Re: lot of white noise when playing an audio source through the SPDIF

You could use the old ADI-2 SPDIF output to feed the ADI-2 Pro, by using the DD mode of the unit (Input LED off). Just to see if inserting the old ADI between U-XMOS192 and ADI-2 Pro makes a difference.

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Re: lot of white noise when playing an audio source through the SPDIF

I've made the experiments you've suggested :

1 - remove the USB cable
     => no effect, same noise


2 - insert the old ADI-2 in digital pass-through mode between U-XMOS192 and ADI-2 Pro
     => no effect, same noise

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Re: lot of white noise when playing an audio source through the SPDIF

And while you do the pass-through you listened to the (same) signal at the ADI-2 analog output? Please do so. If that one is clean and the Pro is noisy then it looks like the Pro is defective. I have no other explanation at this time.

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Matthias Carstens
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Re: lot of white noise when playing an audio source through the SPDIF

Yes, in the digital pass-through mode with analog monitoring, I listened a clean, noise-free, signal at the ADI-2 analog output. As before, the pro is noisy at ADI-2 Pro analog outputs 1/2 but not at analog outputs 3/4. So I tend to agree with you that the ADI-2 pro is faulty.
What is particularly disturbing to me is that it works fine at outputs 3/4. How is it possible ?
Also I notice that the noise is present only when the Kernel Audio Mixer of Windows applies a conversion rate different from 1:1.

At this stage of the problem analysis, do you suggest I should make use of the guarantee ?

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Re: lot of white noise when playing an audio source through the SPDIF

roland.jouanigot wrote:

Yes, in the digital pass-through mode with analog monitoring, I listened a clean, noise-free, signal at the ADI-2 analog output. As before, the pro is noisy at ADI-2 Pro analog outputs 1/2 but not at analog outputs 3/4. So I tend to agree with you that the ADI-2 pro is faulty.
What is particularly disturbing to me is that it works fine at outputs 3/4. How is it possible ?

Easy. Completely separate DAC and analog output path.

roland.jouanigot wrote:

Also I notice that the noise is present only when the Kernel Audio Mixer of Windows applies a conversion rate different from 1:1.

That one I can't explain, it is too strange.

roland.jouanigot wrote:

At this stage of the problem analysis, do you suggest I should make use of the guarantee ?

Sure.

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Matthias Carstens
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Re: lot of white noise when playing an audio source through the SPDIF

Ok, I'll send it to repairs.

There is a question I keep asking myself :
How the ADI-2 Pro knows the difference between, let say, a 192k signal sent by Windows in Excusive Mode and a 192k signal sent by Windows in Shared Mode (ok with the first one, noise with the second one) ?!

Thanks Matthias for the support.

Roland

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Re: lot of white noise when playing an audio source through the SPDIF

I have come up with a new idea:
I remembered that I had an old sound card with SPDIF input/output (TERRATEC PRODUCER/PHASE 22). So I have tried to use it instead of the UXMOS-192 as SPDIF stream to the ADI-2 Pro with the Windows kmixer in shared mode at 96k (the max value supported by the legacy Phase 22). Suprisingly I did'nt hear the unwanted "white" noise.
So this suggests, against expectations, that the ADI-2 Pro is not faulty but instead there is some incompatibility between UXMOS-192 output format (out of spec ?) and the formats supported by the ADI-2 Pro.
There is an explaination in the ADI-2 Pro User's Guide that is somewhat related to this issue :
"But SPDIF and AES can also transport AC-3 and DTS encoded surround sound. This signal
sounds like chopped noise at full volume. Therefore the ADI-2 Pro receiver circuit checks the
Non-Audio flag within the Channel Status. If found the signal is already muted directly in the
receiver. An error message is shown in red colour in the lowest line, saying SPDIF NONAUDIO,
explaining why there is no sound at the analog outputs despite a valid input signal."

As I don't get the "SPDIF NON-AUDIO" message, this suggest to me that the SPDIF signal has some unexpected/exotic characteristics that the ADI-2 Pro cannot properly handle  ...

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Re: lot of white noise when playing an audio source through the SPDIF

Sure. There might be a problem with the DOP 'header' from DSD, which is only supported on output 1/2. This one would even survive the ADI-2 passthrough, as it is within the audio bits. On the other hand the ADI-2 Pro does not switch into DSD mode (unless you forgot to mention that), so the noise must be something different. And the ADI-2 would show the same noise too.

When sending the unit in we would check that PCM and DSD via SPDIF In works as expected. That's all we could do in this case.

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Matthias Carstens
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