CM6631 usb audio interface .... any good ? - Page 26 - diyAudio
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Old 7th March 2013, 08:12 AM   #251
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Join Date: Aug 2007
Quote:
Originally Posted by wklie View Post
Here's RMAA test results of various USB->SPDIF chips. Although the discussions are in Chinese, all the RMAA screenshots are in English and self-explanatory:
USB->SPDIF芯片不完全RMAA测试。内含热门的CM6631测试 - 音响DIY论坛 - HIFIDIY论坛 - Powered by Discuz!

There is a follow up thread that talks about someone modified the CM6631 2205 firmware to correct the Intermodulation distortion anomaly, but I'm unable to find it for now - my google skills are failing me.
Unfortunately his rig isn't up to the job. He's only able to test up to 24 bits, which could be 144dB but his test gear seems limited to 113dB, where everything hits a brick wall.

Even the taobao seller I got my cheapo card from claims he gets 120db from his into an EMU that can do 140dB, and it sounds worse than the diyinhk one.

It seems the bad imd of the cm6631 was because he was running a single 12mhz crystal and he's suggesting adding a 45 and 49 ? Where did you read about modding the firmware ?

If you want to know, then it really has to be tested on 32bit digital rig because the major difference between the firmwares is 24 and 32 bit operation.
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Old 7th March 2013, 08:21 AM   #252
JarekC is offline JarekC  Poland
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Location: Krakow
Quote:
Quote:
Hi,

One again.
Can anyone read USB descriptor of converter based on CM6613/CM6631A.
Here is free software-descriptor dumper to do it. http://www.thesycon.de/tdd/tdd.exe
(no instalation needed)
Then we can compare the versions differences.

BR
JarekC
Quote:
Originally Posted by KlipschKid View Post
I can't, and to be honest, even if I could, I wouldn't spend my time trawling through lines of code looking for differences. Sorry, you need someone far less busy and totally into coding. That's not me.
The result of descriptor dumper is text file with full information about device.
(sampling rates, numer of outputs & inputs, etc)
It is not code.

BR
JarekC
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Old 7th March 2013, 08:45 AM   #253
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jarek - is there a reason you need this ? is there a reason you can't do it yourself ? If I may be blunt, this is DIYaudio, not get-someone-else-to-do-it-audio. if you have a problem or something, then I'll try to help. but I wonder why you insist on asking others to do something it seems you already know how to do. Care to explain ?

Last edited by KlipschKid; 7th March 2013 at 08:49 AM.
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Old 7th March 2013, 02:29 PM   #254
wklie is offline wklie  Hong Kong
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Quote:
Originally Posted by JarekC View Post
Can anyone read USB descriptor of converter based on CM6613/CM6631A. Here is free software-descriptor dumper to do it. http://www.thesycon.de/tdd/tdd.exe
I ran it and got a really long output for my 0108 firmware. If you need it you can PM me your e-mail address.

Interestingly enough it reports a few sections of descriptor errors:

Endpoint Descriptor (Audio):
------------------------------

*** ERROR: Invalid descriptor length 0x07
Hex dump:
0x07 0x05 0x01 0x02 0x40 0x00 0x00

Endpoint Descriptor (Audio):
------------------------------

*** ERROR: Invalid descriptor length 0x07
Hex dump:
0x07 0x05 0x82 0x02 0x40 0x00 0x00
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Old 7th March 2013, 03:08 PM   #255
wklie is offline wklie  Hong Kong
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Quote:
Originally Posted by wklie View Post
Disclaimer: I'm not responsible for any damage that occurs as a result of using these files or these instructions.

CM6631A Firmware 0101 VID 0x0D8C PID 0x0319:
https://docs.google.com/file/d/0B_6Y...it?usp=sharing

CM6631A Firmware 0108 VID 0x0D8C PID 0x0314:
https://docs.google.com/file/d/0B_6Y...it?usp=sharing

To be used with the flash update tool found in the CM6631 Firmware 2203 package VID 0x0D8C PID 0x0309 on Windows XP _ONLY_:
http://www.nutsaudio.com/driver/CM6631_Firmware.zip

Instructions:
- A Windows XP PC is needed (XP compatibility mode on newer Windows does not work - do not try it)
- Connect the CM6631(A) unit to a USB 2.0 port at the back of the PC, do not use the front ports even if available
- Run the flash update tool
- Erase firmware
- Unplug the CM6631(A) unit then reconnect it again
- Update using a new firmware hex file
- If a File Format Error or a Flash Error is shown, reconnect the unit again and flash it again
Found two other firmware for CM6631. Note the PID difference compared to the nutsaudio 2203.

CM6631 Firmware 2205 PID 0304
http://bbs.hifidiy.net/attachment.ph...760&sid=lWbFc2

CM6631 Firmware 2206 PID 0304
http://bbs.hifidiy.net/attachment.ph...760&sid=lWbFc2

I cannot check these firmware, so upgrade at your own risk. These are the differences I've read but cannot confirm:
- 2205 and 2206 PID 0304 add 88.2kHz support missing from 2203
- 2203 PID 0309 does simultaneous I2S/SPDIF output, whereas 2205/2206 PID 0304 only outputs I2S but not SPDIF via ASIO (similar to CM6631A 0108 PID 0314?)
- Multiple reports state that 2203 gives better audio quality than 2205/2206.
- Note that only the two PID 03x9 firmwares for CM6631 and CM6631A are named as UsbDAC, the other PID 03x4 firmwares are not.

If anyone try out these firmware, please post your findings.
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Old 7th March 2013, 03:56 PM   #256
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thanks wklie for your contribution

unfortunatelly there are so many combinations of firmware and drivers with this board that add or delete certain functionalities that I ordered an Amanero board that it's supposed to work up to 352 khz out of the box with no problems and lately they also added ASIO support as well and on Linux I see that it won't even need a driver

we'll see about a sound comparison in an A/B test where the rest of the audio chain remains unchanged, only a fast switch between I2S signals and the DAC
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Old 8th March 2013, 12:28 AM   #257
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Are there any usb-asrc-i2s boards out there ? I'd love to get one that uses an fpga to buffer+upsample to 384khz/32bit.

I got this but the usb is 16 bit, so I'm gonna have to change the usb receiver.
USB/SPDIF TO SPDIF/I2S and ASRC | myl8test

wklie - the 2203 is 32 bit, the 2205 and 2206 are 24bit. I'd bet my last kidney the 32 bit firmware sounds better. Did you have fun trawling through the code to find nothing of use ? ;-) If you like that sort of thing, then run the card through the asio @24bit and 192khz (sox resampler is easy if you use foobar and have no hi-res files), and do the dump. then use the direct sound and force 16bit in foobar and 44.1khz and do the dump. then have fun comparing the two ;-) Do you know hex ? http://en.wikipedia.org/wiki/Hexadecimal

Last edited by KlipschKid; 8th March 2013 at 12:30 AM.
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Old 8th March 2013, 03:18 AM   #258
wklie is offline wklie  Hong Kong
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Quote:
Originally Posted by KlipschKid View Post
the 2203 is 32 bit, the 2205 and 2206 are 24bit. I'd bet my last kidney the 32 bit firmware sounds better.
I can understand with upsampling or digital volume control 32bit would make a difference. However, if one plays raw 44.1kHz 16bit unchanged without upsampling and without digital volume, do you think the firmware being capable of 32bit makes a difference?
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Old 8th March 2013, 03:59 AM   #259
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It would depend on the dac. But it can sound better and I'd bet it's the bit depth that is the reason people say one firmware sounds better than another. Then again, maybe the firmware changes the way the buffer/pll operate together, although I'd think this highly unlikely; it'd be too much work for the engineers to try to have two alternate systems under development within the same chip. So I expect the core operations remain unchanged and the bit depth changes because of an input/output selection, such as dts and four channel outputs, because that'd require more data bandwidth, this a reduced bit depth. However, I'm just speculating.
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Old 8th March 2013, 10:23 AM   #260
ttan98 is online now ttan98  Australia
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Hi Fellows,

Most of you have been using the 6631 or 6631A for a while I have been following this thread and I cannot pretend I understand all the techinical aspects related to these models.
If someone can recommend me a model to buy at Ebay I would appreciate it. I have my eye on this model:
eBay Australia: Buy new & used fashion, electronics & home d?r

what do you think?
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