C-MEDIA CM6631 USB-to-S/PDIF receiver

Cubietruck related support

C-MEDIA CM6631 USB-to-S/PDIF receiver

Postby bejoro » 23 Dec 2015, 21:15

I have got an USB DAC with a C-MEDIA CM6631 USB-to-S/PDIF receiver.

I am using DLNA with BubbleUPNP to control RuneAudio on my CubieTrucks.

There is this sample rate change bug with C-MEDIA CM6631 receivers.

Is there a fix for this bug?

Thanks.
Best regards,
Bernhard
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Re: C-MEDIA CM6631 USB-to-S/PDIF receiver

Postby bejoro » 03 Jan 2016, 08:31

I would appreciate any help.

I would like to use the very nice Meier Audio DACCORD with RuneAudio. A really nice DAC with great features also especially for headphone users.

There is cracking noise if you change tracks manually.

More important, the CM6631 does not recognize a sample rate change correctly. You have to pause the track and start again, then it works.

It seems that there is an ALSA fix or patch.

I would need instructions how to implement that ALSA patch.
Best regards,
Bernhard
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Re: C-MEDIA CM6631 USB-to-S/PDIF receiver

Postby hondagx35 » 03 Jan 2016, 12:42

Hi Bernhard,

your Cubietruck has an onboard optical SPDIF output which works very good.
Is there a reason for not using this instead of an external usb to SPDIF converter?

.... the CM6631 does not recognize a sample rate change correctly......
It seems that there is an ALSA fix or patch.

I do not own such a device, so i can not test this.
Can you point me to a resource for this fix?

Frank
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Re: C-MEDIA CM6631 USB-to-S/PDIF receiver

Postby bejoro » 05 Jan 2016, 19:05

Hi Frank,

The whole device is a very good D/A converter with digital inputs and one USB input. I think it is available since 2011 and XMOS was not so popular at that time already.

The USB input uses the CM6631 USB to SPDIF receiver which has the mentioned sample rate change bug.

The CM6631 is connected to a Wolfson DAC which has a very good SPDIF input with ultra precise clock, extreme low jitter etc. That's why the unit uses the USB to SPDIF decoder.

Sorry if I do not point to a link or page, because I do not know what you need.

But you might google for "CM6631 sample rate change bug". This would lead you to several pages of ALSA patches, different versions.
Best regards,
Bernhard
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Posts: 10
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