Calling XMOS and CM6631 experts

ttan98

Member
2006-04-04 11:24 am
Melb
Hi,

There are currently 3 options to convert USB to SPDIF/I2S which are based on:

1. TE7022
2. CM6631 or CM6631A
3. XMOS

The 1st one is considered a little old and the max speed limited to 96kbit/s. The last 2 chipsets, CM6631/A and XMOS are current chipset used in the current crop of convertor designs. I bought a convertor based on CM6631 and I found it to very good at the same time it is quite cheap.

I don't know the differences(technically) between the CM6631 and XMOS chipsets, my query is that, is there a clear/distinct advantage, e.g. jitter spec. of the XMOS chipset over the CM6631/A? If so please explain. If I am getting a new convertor should I buy a convertor based on XMOS or CM6631A? Thanks.
 

Hugh Jazz

Banned
2013-02-15 5:19 am
Hi,

I am not the expert. But I have all these and I learn little bit. Tenor is isochronous and good but not the same level as the asynchronous. CM and XMOS are asynchronous. You know this and understand this difference ?

CM use the higher speed XO (good for ES9018 DAC in synch mode but xo on CM is not the best so not the best for Es9018 ?). It make the mclk as division inside the IC - maybe add little bit jitter ? It have both mclk always on. I guess it have a slower bus speed because it not get hot and maybe it have smaller buffer... maybe. I guess it is single core processor.... guesses.

XMOS is multi-core. It use the common speed xo and turn off/on. It does not divide mclk so mclk is sent direct, not through IC. Buffer depend on the IC but usually 64K or maybe 128K.

Both have asio driver for windows. Don't know for mac / linux ...

There are some CM to choose and some are very good, some not as good because of the layout, component choices, etc. There are some XMOS - Matrix, Lurien WaveIO, Diyinhk DXIO, MiniDSP USB streamer ....

So, I think you need to say which DAC, which OS, etc. Then people can make the recommendation to you.

I think XMOS is sounding better than CM6631 anyway.

http://www.diyaudio.com/forums/digital-source/217764-cm6631-usb-audio-interface-any-good.html

http://www.diyaudio.com/forums/digital-source/233926-new-xmos-usb-384khz.html

http://www.diyaudio.com/forums/digital-source/188902-xmos-based-asynchronous-usb-i2s-interface.html

http://www.minidsp.com/products/usb-audio-interface/usbstreamer

http://www.ebay.com/itm/ws/eBayISAP...51192844815&item=251192844815&vectorid=229466

And there are more options. There is Amanero, Musiland... and more.
 
Last edited:
Both links that you've provided are no longer available.

Anyway, a problem that the AD1865 has is that it takes input in an 18-bit serial two's complement MSB first format. Most available USB to I2S converters provide exactly that : I2S. You'll have to be able to provide glue logic to convert the I2S into the format needed by AD1865.

There ARE projects in this forum though that would be able to address that. I think I saw somewhere that Ian is developing (has developed) a board that simplifies connecting NOS DACs to I2S sources. Not sure if it's ready for use .... Look it up. :)

Another option though is Joro's I2SOverUSB board
http://www.diyaudio.com/forums/group-buys/237301-gb-thread-xmos-dsd-384-khz-32bit-usb.html

His XMOS implementation is capable of directly providing input for your AD1865 NOS DAC. You just need to configure it to output for AD1865 using resistors.

I'm using this board by the way, feeding an AK4396 DAC, and it sounds VERY good.

Hi!
I am a bit confused. I read so many pro and contra about theese devices. (Xmos and CM6631)
One question:
Which one would be good for a classical NONOS AD1865 DAC???

- 24/192 , 24/96 CM6631 USB to COAX OPT SPDIF convertor for DAC - PCM270X killer | eBay

- Commpleted 192K 24bit Xmos USB to Fiber Coaxial Output I2S Asynchronous WLX | eBay

Greets:
Tyimo
 

hyperma

Member
2008-10-04 5:53 am
The Xmos much better

The sound quality of CM6631A is same as Xmos if well designed.Sometimes it not works well on the computer,you can hear pops frequencly......very high possibilities.....

After 3 months suffering,I found the reason,you have to remove some devices drivers and keep the starting menu as clean as possible,anyway,to have fun with CM6631A is not an easy question.
 

3nity

Member
2009-04-06 8:28 am
The sound quality of CM6631A is same as Xmos if well designed.Sometimes it not works well on the computer,you can hear pops frequencly......very high possibilities.....

After 3 months suffering,I found the reason,you have to remove some devices drivers and keep the starting menu as clean as possible,anyway,to have fun with CM6631A is not an easy question.

Curious to know, which driver did you have to remove to achieve the CM6631A fully working state?

TIA
 
Hi Hyperma!
The sound quality of CM6631A is same as Xmos if well designed.Sometimes it not works well on the computer,you can hear pops frequencly......very high possibilities.....

After 3 months suffering,I found the reason,you have to remove some devices drivers and keep the starting menu as clean as possible,anyway,to have fun with CM6631A is not an easy question.

After some week without any problem, now I am in the same situation too: "pops" are coming.
What device drivers should I remove???

greets:
Tyimo