Hello,

my Opus/WM8804 combi is up and running. There is only one problem left. Every time when there is no spdif source connected to the wm8804, this happens every time I switch on my system, I hear a really annoying noise. In addition to that, my cdp seems to generate no (or no valid) spdif when I change the disc. As a consequence I hear the changing of the disc through my speakters either as one or several clicks or as the same annoying noise like on startup (changes from time to time). My old DAC combi (Opus Prototype with CS8416 onboard) did not show these problem with the same cdp

Here in the forum noone reported this problem, or I did not find the post.

According to the Datasheet, there is a Flag to control the behaviour in the case of corrupt or invalid data (FILLMODE) in software mode as far as I understand. But in hardware mode, there is no possibility to influence this behaviour.

Any ideas?

Best regards

Flo

Hi Brain,

thanks for the quick reply.

At the moment I am running a Stereo Opus that will be converted to dual mono as soon as my DAC arrives (the planes fly very slowly these days). My layout has already been posted here:



the wm8804:



and the DAC:



Mono on the DAC-Board is now set to 1 - I thought this could have been the error. And the IWO switch is in the correct position now too.

For the power supply-wiring: I use your dual supply, one for the analog section, one for digital. The digital section also supplies a LM7905 that supplies a relais-board similar to darwin but built on stripeboard.

- The analog ground is tied to the straground of my preamp.
- The digital and the analog ground meet each other on the DAC as far as I see.
- The spdif wires (not on the picture) are wired to the spdif input directly.

Do you think, that the grounds (analog and digital) should be linkes "offboard"? Together with the spdif-ground?

At about 3 cm from the i2s wires there is the lm7905 located that is supplied by 7,5V DC and that supplies the relais-board - the load of this part is really static.

Best regards

Flo

I don't connect the power gnds anywhere except to the power supply. The signal gnd (audio out from the DAC) will meet the analog gnd of the RCA inputs in the preamp/amp (I don't think this is the source of the noise though)

I don't see anything wrong with your OPUS switch settings. Perhaps you might be interested in this post regarding how OSR works (again this will not solve your noise problem, but it might improve your sound :-))

Thank you for the answers,



My DAC is in the pre, thats the reason for the connection to the star ground.



Thank you, very interesting reading. But as far as I understood at a glance, I would need to work in sw-mode then. I wanted to avoid this.



I think that if I ha a problem with the PS (or the wires), I would have the noise in every case, if the spdif source is switched on or not. But the noise only appears if the source is switched off, or if it's loading a cd. When the source is on, no matter if there is a cd in the tray or not, the DAC is "dead quiet".



Regards

Flo

Oh, should have looked better, thanks.

Edit: Which setting do you prefer for 44.1/48kHz input?

Edited by user Wednesday, January 5, 2011 2:59:11 PM(UTC)  | Reason: Not specified

I have never seen this before. If there is no SPDIF signal the receiver should be transmitting silence. It could be that the output of the SPDIF module is damaged, or perhaps the input of the Opus. Otherwise it is likely a wire routing or power supply issue.

Hi Russ,

I use the LCDPS for the digital and analog part of the DAC. Should be fast enough ;-). It's set to 8V an each rail.

I think that a wiring issue and a defect of the spdif transmission should affect the sound even with an spdif source present. Am I wrong?

Regards

Flo

LCDPS is fine.

Opus does not accept SPDIF.

Do you have OSR set to match your sample rate?

Update:

Changed the osr setting to low. The noise on startup dissapeared, the noise when reading in an new cd remained. Now its a "buzzing" like sparks from electrical voltage. All the LEDs on the wm8804 flicker when this appears.

This might be an error of the cdp. But the old Opus with cs8416 onboard did not show this effect.

So there are some questions left:

- What's the reason for this buzzing? How could it be avoided?

- Why does the startup noise dissapear when I change the osr setting? Medium osr should work with 44.1kHz too. Apart from this, how does the reciever/dac know, which kind of signal is going to come when there is no signal present? As far as I understood will the reciever accept any sampling rate and transmit it to the dac.

- What will happen if osr is set to low but I transmit signals with a sampling rate higher than 48kHz via spdif? That's going to happen when this setup is ready and I start to digitalize my favourite LPs.

Thank you so far. And best regards

Flo

If you input a higher sample rate than 48K signal and set the OSR to low, you are telling the DAC to do a 4X oversampling which it cannot support. The DAC will either be silent or output constant static (I tried this in s/w mode and with a Metronome - I don't remember what caused silent and what caused static).

When I was using the WM8804/WM8741 OPUS, I was able to use all 3 settings of the OSR with 44.1K material and had no buzzing issues. The WM8804 was in h/w mode, the WM8741 was in s/w mode.

I think the DAC should have an automatic OSR mode but it doesn't. In s/w mode you could read the sample rate reported by the receiver and then program OSR accordingly