2. pc-audio
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Looking for upgrade from Apple TV, would like to keep using iTunes and wifi

My wifi-based sound has never matched my dear departed Arcam Alpha 9 CD player.  I've read forum after forum but I don't see a simple solution.  One possibility is that an audible problem occurs when the bit rate is changed from the CD native 44.1 kHz bit rate to the more traditional 48 kHz.

Here is my wifi system: iMac (iTunes) -> wifi -> Apple TV -> optical TOS -> PS Audio Digital Link DAC. 

The 300GB of music has been ripped from CD and is stored using Apple Lossless compression.

Yes, I know it's a lot of Apple software and gear.  I want to keep the iMac and iTunes and the wifi link.  I like the playlist features of iTunes, including the Genius feature. 

The Apple TV comes with a remote control and I can access the iTunes playlists directly, using my TV as a monitor, even though the iMac is in a separate room.  Once the playlist is playing I turn off the TV.

I am an electrical engineer and I've even worked measuring jitter on serial bit streams.  I understand that converting from 44.1 kHz to 48 kHz will cause some sort of interpolation error whereas converting from 48 kHz to 96kHz can be done with no trouble.  However, the Apple TV outputs 48 kHz so the bit rate must have been changed somewhere along the chain.  My PS Audio DAC won't even lock to the native CD rate of 44.1 kHz.

Are there any suggestions for a wifi receiver and DAC that will match the sound of a good/great CD player?  The budget is about $600, with an upper limit of $1000.

Thanks
pmiguy

Showing 2 responses by pmiguy

pmiguy OP
9 posts
 
I don't see an easy solution for me yet.

This is getting pretty technical but here goes:

My DAC has two lights on the front, 96 kHz and 192 kHz.  That's why I assume it will lock to 48 kHz (double rate upsampling) but not lock to 44.1 kHz.  An interesting experiment for me would be to run a CD player output into my DAC and see if the LOCK light comes on (assuming the CD player would output 44.1 kHz).

Any upsampling DAC will reclock the data using a PLL generated clock.  The PLL has natural jitter reduction.  I'm not sure that adding another jitter reduction device would help much.  Most jitter reduction circuits are probably just using PLL reclocking anyway.

Interpolation for a 2x sample rate should be fairly easy, maybe just average the adjacent samples.  Interpolation for a 48/44.1 ratio would be computationally complex.  I doubt that the AppleTV does the interpolation well.

I do have a 10 year old Mac Mini that I can pull out of storage.  It has USB 2.0 and also an optical output.  Maybe the local server is the way to go.



pmiguy OP
9 posts
 
I like the idea of Async USB.  Why rely on the computer to do the timing?  It's better to let the DAC do the timing. 

I'll see what I can do with my old Mac Mini and the DAC that I have.  Eventually I may be in the market for a USB to SPDIF convertor or a new DAC.  I may look at the Remedy solution also.

Thanks everyone for the quality discussion!
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