CM6631 usb audio interface .... any good ? - Page 8 - diyAudio
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Old 27th November 2012, 02:38 PM   #71
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Join Date: Dec 2008
glad if I could help, please keep us updated how your firmware upgrade went and what improvements did it bring (I am mostly interested over an I2S connection using ASIO driver for bit-perfect reproduction)
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Old 2nd December 2012, 02:34 AM   #72
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Hi DIYINHK!
I purchased your CM6631 usb-ddc and several Japanese Audiophiles are now trying to connect their DACs. I'm looking forward the arrival of the device.

Is it possible to use this device with Linux e.g. Voyage MPD? According to one of the most famous Audio DIY-BBS in Japan, this device can be recognized with Linux with ALSA1.0.23, kernel 2.6.35 or later, however the sound was gradually 'choppy' (=in fragment; spdif) then system (driver?) was frozen.

Could you check and let us know about detail information about Linux?

Regards,
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Old 7th December 2012, 03:21 AM   #73
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Join Date: Sep 2012
Thank you for interesting in our product!
The 29.95 version pcb is target for highest price to performance ratio, it uses 15ppm NDK crystal from digikey, 50ppm KDS oscillator from shenzhen
We will have an galvanized isolation version with dual ultralow noise regulator and 15ppm NDK crystal+25ppm FOX oscillator all from digikey. It's target for the most demand Audiophiles
The SPDIF is a standard signal specification, the frozen problem should related to the software player. I recommed use I2S directly rather than SPDIF, all DAC convert SPDIF back to I2S to decode. It avoid one more unnecessary layer.

Quote:
Originally Posted by TMKYoshi View Post
Hi DIYINHK!
I purchased your CM6631 usb-ddc and several Japanese Audiophiles are now trying to connect their DACs. I'm looking forward the arrival of the device.

Is it possible to use this device with Linux e.g. Voyage MPD? According to one of the most famous Audio DIY-BBS in Japan, this device can be recognized with Linux with ALSA1.0.23, kernel 2.6.35 or later, however the sound was gradually 'choppy' (=in fragment; spdif) then system (driver?) was frozen.

Could you check and let us know about detail information about Linux?

Regards,
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Old 22nd December 2012, 06:01 AM   #74
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Join Date: Aug 2007
Hi,

I finally finished the CM6631 + AMB y2 build so here are some pics. I can switch between USB and external power so it can get clean power from a linear psu. In which case noise can only enter through the USB D+/- lines, so I'm not sure I will need to add an adum3440 isolator. However, there is space to try one, so, maybe. :-)

Anyway, it sounds good and the linear psu really helps. USB power is not as good - usb power has noticeably more mushy treble and harsh vocals, with less bass definition.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

And with a 30V Mini3

Click the image to open in full size.

Last edited by KlipschKid; 22nd December 2012 at 06:12 AM.
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Old 24th December 2012, 12:16 PM   #75
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The adum3440 arrived today. I don't have a wide body adapter pcb, so I cut a regular sop16 in half, soldered on the adum, and then used epoxy putty to make a very strong bridge. I'll try fitting it after the holidays, to see if it makes a difference.

Click the image to open in full size.

Merry Christmas !

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Old 25th December 2012, 06:04 AM   #76
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Hi, pls explain why have you chosen this particular adum chip? I see from the datasheet that is a highspeed multichannel isolator but it is not designed specially for USB isolation; why am I telling this? because looking to the ADuM4160 datasheet that was specially made for USB data (D+ and D-) data isolation, it is stated that
"USB lines must automatically switch between actively driving D+/D−, receiving data, and allowing external resistors to set the idle state of the bus. The ADuM4160 provides mechanisms for detecting the direction of data flow and control over the state of the output buffers. Data direction is determined on a packet-by-packet basis"

do you think your current chip behaves in the same way?
I am curious about your results with this chip, and judging by the datasheet is being able to support 150 Mbs (in contrast with the adum4160 that can support only 12 mb thus limited to only 24bit/96khz) so that means it could easily handle even 32 bit 352 khz sampling rates over I2S.
keep us updated pls if you succeeded and also with the sound impressions after the isolation, thanks
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Old 25th December 2012, 10:23 AM   #77
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Merry Christmas !

I plan to use on the I2S - but I could try it is on the usb lines, perhaps just to confirm it doesn't work. The 3440 does bi-directional flow according to the datasheet, but I don't know enough about usb protocols to know if this is enough. Probably not, but there's no harm trying.
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Old 25th December 2012, 10:57 AM   #78
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Merry Christmas for you too!

for I2S isolation better choice would have been the quadruple ISO7240 which has only 1ns eye pattern skew jitter declared for the 150 Mbs speed, or high speed cmos optocouplers like HCPL-7723 which have only 2ps jitter;
the ideea is not to add more jitter than you would achieve without isolation, better said not to do more harm than good
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Old 25th December 2012, 11:12 AM   #79
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7240C has noise filter but is only 25Mbps; 7240M does not have noise filter but is 150Mbps. There doesn't seem to be one that does both noise filtering and 150Mbps ? Optocouplers have issues apparently - never tried them myself. I have used adum4160, and heard the improvement so I know AD's isolators do the job.
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Old 25th December 2012, 11:28 AM   #80
syklab is offline syklab  Hong Kong
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Location: Hong Kong
Quote:
Originally Posted by KlipschKid View Post
Merry Christmas !

I plan to use on the I2S - but I could try it is on the usb lines, perhaps just to confirm it doesn't work. The 3440 does bi-directional flow according to the datasheet, but I don't know enough about usb protocols to know if this is enough. Probably not, but there's no harm trying.
Hi ,
Merry Christmas!
Couldn't wait to heard your result.

Enjoy the holiday.
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