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Old 4th February 2013, 09:22 PM   #151
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Quote:
Originally Posted by tdtsai View Post
I know why alsa driver does not work in CM6631 device. The problem is set sampling rate time. Alsa driver set clock unit after select interface, its different with mac osx driver. if you change set clock unit before select clock unit then alsa driver can work fine.
I have one of these ebay devices. The only problem I have found using it under Linux and ALSA is that it has problems playing sound with the right sample rate. A quick "pause/play" click solves the problem and it locks to the correct sample rate. However this is not acceptable... This is a known problem and you are mentioning a solution to it.

How can I configure ALSA to set clock unit first? Can it be done in some configure file? Is there a patch? Do I need to change the source code and recompile? Pleeeease tell me
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Old 5th February 2013, 03:42 AM   #152
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Quote:
Originally Posted by triode_al View Post
Thanks. This was my thinking too.

Other question:
  • is this a synchronous or a-synchrous application? (looks like a pun, zen guys would love it).
  • I have understood asynch to offer best click-less working in other threads; now I understand it is claimed that with the Sabre interface the normal old fashioned synch gives a better result, without un-lock clicks.
  • would that go for other I2S DAC too (like my silly old fashioned TDA1541?

    albert :-)
Hi,

CM uses asynch to receive/process usb data. This is usually better than synchronous usb data transfer, and in this case it's much better than the TE7022L and pcm270X etc.

Sabre DAC is special - it can use any clock asynchronously to the I2S source - but gives the best sound quality when the clock is synchronised with the I2S clock.

I2S is I2S. TDA1541 uses SAA receiver for I2S - does that have an independent clock input ? I think the question of synch/asynch is irrelevant for SAA. Better to ask a NOS expert about this.

cheers
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Old 5th February 2013, 09:53 AM   #153
tdtsai is offline tdtsai  Taiwan
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Hi Arcturus:
C-Media has new firmware for CM6631A to fix this issue. But I don't know does there is new firmware for CM6631. But the easy way is to modify ALSA driver. Yes you need to change the source code and recompile.
Quote:
Originally Posted by Arcturus80 View Post
I have one of these ebay devices. The only problem I have found using it under Linux and ALSA is that it has problems playing sound with the right sample rate. A quick "pause/play" click solves the problem and it locks to the correct sample rate. However this is not acceptable... This is a known problem and you are mentioning a solution to it.

How can I configure ALSA to set clock unit first? Can it be done in some configure file? Is there a patch? Do I need to change the source code and recompile? Pleeeease tell me

Last edited by tdtsai; 5th February 2013 at 10:05 AM.
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Old 5th February 2013, 10:02 AM   #154
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Originally Posted by wklie View Post
I enabled them but no sound at 88.2 kHz. I think that earlier in this thread you got foobar ASIO output to SPDIF working, right? Would you mind telling me what's listed in your foobar ASIO channel map? Thanks.
Hi, you could check post #68 and #69 in this thread where I linked the driver and the firmware what is used to enable SPDIF or I2S (but not both at the same time); remember to do this procedure ONLY under WIN XP cause WIN7 has issues and gives errors on these updates

CM6631 usb audio interface .... any good ?


my question for those who use this card on linux is wether ALSA driver is able to output SPDIF and I2S at the same time?
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Old 5th February 2013, 10:07 AM   #155
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Quote:
Originally Posted by KlipschKid View Post
Hi,

CM uses asynch to receive/process usb data. This is usually better than synchronous usb data transfer, and in this case it's much better than the TE7022L and pcm270X etc.

Sabre DAC is special - it can use any clock asynchronously to the I2S source - but gives the best sound quality when the clock is synchronised with the I2S clock.

I2S is I2S. TDA1541 uses SAA receiver for I2S - does that have an independent clock input ? I think the question of synch/asynch is irrelevant for SAA. Better to ask a NOS expert about this.

cheers
This clarifies a lot. It is the local connection to the Sabre that intentionally is synchronized. I understand, that is why others want reclocking.
The TDA1541 does not need the SAA-chipset; it can handle a direct I2S input in NOS (44.1 kHz), but also oversampled in the computer, 88.1 KHz or double that; and any bits beyond 16 bits are stripped. [If I understand correctly]
Similar to TDA1543.
  • Hypothesis: The SAA7220 digital filter has a buffer and runs on an input clock. Probably also there a synchronous connection is needed (distributing the clock, half or quarter clock . . .).
    I think that is reason for connection to Sabre in the specified way.
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Old 5th February 2013, 10:26 AM   #156
UnixMan is offline UnixMan  Europe
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Quote:
Originally Posted by tdtsai View Post
I know why alsa driver does not work in CM6631 device. The problem is set sampling rate time. Alsa driver set clock unit after select interface, its different with mac osx driver. if you change set clock unit before select clock unit then alsa driver can work fine.
interesting. Sounds like an easy fix, which should not interfere with other chipsets (and going toward a more "standardized" behavior between different OSs is IMHO a good thing).

Have the ALSA driver developers been informed about this? If not, we should do that ASAP!

Quote:
Originally Posted by Arcturus80 View Post
How can I configure ALSA to set clock unit first? Can it be done in some configure file? Is there a patch? Do I need to change the source code and recompile? Pleeeease tell me
I'm afraid this is not something that can be changed in a config file: sources need to be modified, and drivers rebuilt.

Perhaps tdtsai may already have / suggest a patch?
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Old 5th February 2013, 10:37 AM   #157
tdtsai is offline tdtsai  Taiwan
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Hi UnixMan:
I think no one informed ALSA driver developers. Because no one tracing this issue.

Quote:
Originally Posted by UnixMan View Post
interesting. Sounds like an easy fix, which should not interfere with other chipsets (and going toward a more "standardized" behavior between different OSs is IMHO a good thing).

Have the ALSA driver developers been informed about this? If not, we should do that ASAP!


I'm afraid this is not something that can be changed in a config file: sources need to be modified, and drivers rebuilt.

Perhaps tdtsai may already have / suggest a patch?
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Old 5th February 2013, 11:03 AM   #158
tdtsai is offline tdtsai  Taiwan
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Hi wklie:
Basically CM6631A can do 6 channels output(Speaker Out, Headphone Out, Spdif Out) 6 channels input (Microphone In, Line In, Spdif In) at the same time. CM6631A has MCU inside so you can programming it then change it to what you want.
Can you tell me the URL about say native ASIO driver is incompatible with everything except foobar? I want to check it. Do you need to add spdif out support in native ASIO driver? If you need it please PM me.

Quote:
Originally Posted by wklie View Post
Thanks tdtsai! You are correct! Mine is really using 0x0D8C/0x0314. May I ask from where can these PID - ASIO relationship information be obtained?

Thanks to KlipschKid for your help too!

I discussed with the seller before reading this message. He sent me a newer driver package (other than including a Windows 8 directory, the other file dates are the same as July 2012 drivers), which does not fix this issue. I raised the possibility that maybe a different firmware is required for the driver to show SPDIF instead of Speaker/Headphone, but he does not think this is the case. Instead he believes there is some problem with my PC settings.

Now I can put this issue to rest. I just need to learn the truth, and hoped to try out the native ASIO driver, in the unlikely event that I can hear an improvement over ASIO4ALL, which works well. I don't really have to use the native ASIO driver. Someone from a Chinese forum tested its compatibility with eight different player software, and found that is incompatible with everything except foobar.
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Old 5th February 2013, 12:43 PM   #159
wklie is offline wklie  Hong Kong
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Originally Posted by tdtsai View Post
Hi wklie:
Can you tell me the URL about say native ASIO driver is incompatible with everything except foobar? I want to check it.
转让全新佛山伟良CM6631 高端USB转同轴加光纤、独立电源0.5-1PPM高精版整机 二手交易与购买咨询区 耳机大家坛 - powered by phpwind.net
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Old 5th February 2013, 12:56 PM   #160
wklie is offline wklie  Hong Kong
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Originally Posted by luxury54 View Post
Hi, you could check post #68 and #69 in this thread where I linked the driver and the firmware what is used to enable SPDIF or I2S (but not both at the same time);
Hi luxury54, I did try the linked driver before. I think that driver is the April 2012 version, which refuses to install on my setup (cannot detect the CMedia USB) - perhaps because it's expecting CM6631 instead of CM6631A.

I also looked at the firmware zip and the pdf inside. This firmware is the 2203 version. I do not dare to try this out because (1) I cannot restore to my current firmware if it goes wrong; and (2) I'm afraid it might not support CM6631A.

If I were to go through a firmware reflash, it's not clear to me how to choose SPDIF or I2S (different PID?) - could you explain that? Thanks.
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