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RE: cMP - the open source high-end Memory Player

First, I have powered the Juli@ analog section separately, but it was still mounted on the digital section.

The sound quality improvement was stunning... one of the four top improvements I've had while tweaking out my cMP. Most striking was the increased senses of clarity, purity, sweetness, and dynamics.

I posted about this and also listed some of the connector pinouts in this sub-thread:

http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=48851

Sorry, I didn't list all of the data and control pinouts on J3. If you are using the just the analog out of the Juli@ and don't intend to use the A-D portion, you won't need most of the non-listed J3 pins, likely just a few that control the signal mixers.

Separate power to the analog card is well worth it. You'll need at least a +5v and a +-12 supply.

And the AK4358, while not the most modern DAC, sounds very nice in this implementation. I've considered re-doing a Juli@ analog portion while bypassing the mixing and op-amp output stages to see how good I can make it.

One caution in doing what you plan, though... the connections from the Juli@ digital section to the analog section are in I2S format. This is not a format designed for long runs... anything longer than a few inches will cause signal integrity degradation. While it will work, it won't work as well as short connections. BUT, there are a couple of devices that can help you in this regard...

First, and available now, is the K&K I2S interface. It uses the same protocol and process as on the latest PS Audio Transport & DAC to support a long I2S interface using an HDMI cable. You can see it here:

http://www.kandkaudio.com/digitalaudio.html

One benefit is that they already have a version designed to pick up the output I2S signals from a Juli@ & pass them to a remote DAC, so there's less work to do to parse the J3 pinout. Of course, you still need to determine if you need any of the other pins (like the mixer ones I mention above).

Then there's a soon-to-be-released Bit-Teleporter from Twisted Pear Audio. It uses similar devices to the K&K / PS Audio interface to perform a similar function for I2S signals, but is intended for use with a network cable instead of an HDMI cable. You can see it here:

http://www.twistedpearaudio.com/digital/teleporter.aspx

and find a bit more information on it here:

http://www.diyaudio.com/forums/twisted-pear/201106-introducing-bit-teleporter-2.htm

Both of these provide some isolation from the noise generated in the computer as they use non-ground-referenced differential signals. Not quite as isolated as opto-couplers or GMR's, but they do provide the ability to drive pretty long cables.

There's further discussion of I2S isolation here:

http://hifiduino.wordpress.com/2011/11/24/which-digital-isolators-for-i2s-or-not/

I'm currently using alternative DAC cards mounted on the Juli@ digital and opting for keeping my I2S connections very short in an attempt to minimize degradation. My intention is to try isolation using both the TP Bit-Teleporter and the IL715 GMR, both of which seem to be pretty easy to implement.

You can read more about what I'm currently up to here:

http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=96880

Greg in Mississippi

P.S. The other three top improvements in my cMP?

First, implementing the Linear-Hybrid ATX power supply. It was a large step from even a modified computer SMPS. While a fully-linear supply is even better and almost as large of a difference, the Linear-Hybrid difference is a leap to another dimension while the move to a fully-linear is a huge refinement, but within the same sonic context as the Linear-Hybrid.

Second, performing the initial Windows-slimmings that were pioneered by Steppe. I'm only up through Steppe 5 or 6, but that progression was an eye-opener. I'm eager to find the spare time to go the rest of the way.

Third, performing the Juli@ digital section mods that I hint at in the last link above. While I've got a lot more I need to try (under-volting, alternate clocks, and I2S isolation being the main ones remaining), the sonic upgrades wrought by these somewhat hard-to-perform tweaks to the digital section are in the same class as the ones above.
Everything matters!


Edits: 02/27/12
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  • RE: cMP - the open source high-end Memory Player - GStew 19:49:32 02/27/12 (0)
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