CM6631 usb audio interface .... any good ?

[Pano]

Klipschkid, please read this thread an consider it when posting your photos with giant files sizes.
Pictures -- Why Not attach Them ??
Thank you.

[KlipschKid]

Seller has asked me to delete the image of the underside of his board; so if they are missing above, you know why. I have deleted it from Flickr. Sorry. I suggest you contact the seller if you want to see it. There's so much copying in this part of the world, it's a perfectly reasonable request.

Pano - is this a browser problem ? The images resize automatically on every PC I use. What exactly is the issue ? Anyway, feel free to delete post 45 and any offending pictures. Please accept my apologies.

[luxury54]

thanks for your answers, although I must say that I find it a little bit strange that all of you who replied in favor for that design are from the same country as the ebay seller of this design, having the HK flag beside your usernames...maybe coincidence

[diyinhk]

Originally Posted by luxury54

thanks for your answers, although I must say that I find it a little bit strange that all of you who replied in favor for that design are from the same country as the ebay seller of this design, having the HK flag beside your usernames...maybe coincidence

this pcb ship from HK, local people should received it faster
our lastest well known design is ddc pump pcb in the water cooling world,
many diyer are happy with it's performance, google is good source for it.
negative comment is also welcome to improve this pcb

[luxury54]

thanks for your clarification, I saw that you provide also a board which has optical output already mounted, so my question is if you could provide a board with coax SPDIF output mounted instead of optical (with or without isolation transformer), since coaxial electrical output is well known in the audiophille world to sound much better than optical, thus many buyers would be searching for such a design instead of optical output.

[diyinhk]

Originally Posted by luxury54

thanks for your clarification, I saw that you provide also a board which has optical output already mounted, so my question is if you could provide a board with coax SPDIF output mounted instead of optical (with or without isolation transformer), since coaxial electrical output is well known in the audiophille world to sound much better than optical, thus many buyers would be searching for such a design instead of optical output.

All DAC convert SPDIF to I2S signal before decode.
Use I2S is far better than using one more SPDIF layer
The best way to get low jitter/highest quality sound is using I2S feed to the DAC chip directly. The optical SPDIF on the other pcb is just for user's convenience

[KlipschKid]

Originally Posted by diyinhk

this pcb ship from HK, local people should received it faster

...I thought it was because we are such generous, talented and modest people ;-)

Originally Posted by diyinhk

negative comment is also welcome to improve this pcb

Hi,

For the I2S, you might consider (if you didn't already) :
- 22r smd low inductance resistors near the IC
- remove the kinks in the lines
- fan them out and add ground pours (with a few vias) in between the lines
- go back to the original GSGSGSGSG

For the usb power, you might consider (if you didn't already) :
- use two regs - one for the 3 xo's and one for the rest
- add a cap multiplier before each reg (BC550, 100uF and a suitable collector-base resistor)

Although I2S usually sounds better, many people need spdif, so you should think about adding the circuit I used above just to please the people, but don't please them too much = use a 75 ohm BNC, not RCA. RCA is a joke for digital.

For the hard core people, you might consider using Crystek CCHD-957 xo - ultra low phase noise makes a real difference, but they're US$30 each, so maybe just allowing this option would be enough.

Finally, a 4 plane board with 2 ground planes would be sweet, and it'd stop people copying your design.

Just my 2 cents from what I've learned form the great people here at diyaudio.

Actually, the board sounds very good as is, so there's no real need for changes.

[syklab]

How about an isolator for the I2S feed?

[KlipschKid]

Originally Posted by syklab

How about an isolator for the I2S feed?

I'd love it too. How would you do this ? There are four lines ... four transformers ? Maybe two adum4160 isolators ? I haven't thought of a good way to do it, but I really hope someone has thought of it - any ideas ?

[syklab]

How about the ADuM6400? Got 4 data channels with enough bandwidth. Got a sample chip but haven't got time to try it out yet?

Ian got a nice isolator board but not yet in production.