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Micro DAC: USB vs. optical connection

post #1 of 6
Thread Starter 
My setup is:

wireless iTunes streaming via Airport Express --> 8" optical cable --> Micro DAC --> Hornet --> HD600 with stock cable

I have my music ALAC on itunes. I noticed that switching from USB to optical input added more body and impact to each note, with slightly more detail overall. However, the notes seem hazy around the very outer edges, "blurry" in a sense. Would this be due to the ultimate shortcomings of the Micro DAC//Hornet, or jitter? Songs through USB seem more "polite" in a sense (as if the haziness on the edges of each note are smoothed over and not presented); I'm wondering if this is because such details are not manifested as much through USB (I'll blame it on kmixer if so).

Another improvement through optical is greater stereo separation. Sounds are better defined and presented at the extreme left and extreme right of the soundstage, giving the impression that the stereo separation has increased. For example, on Radiohead's "Let Down" track at 4:00, the two voices at the extreme left and extreme right are better defined and presented more realistically. Through USB, it sounds like the voices are "chopped off" or "blocked" at the left and right extremities; through optical they have fuller body and realism. It was a mind trip when I first heard this song through optical

Overall I like the optical connection more than USB, even though it is more of a hassle with wireless streaming. When you click to play a new song, jump within song, or pause a song then start it up again, I hear a faint hiss during a slight pause period before the 1s and 0s are wirelessly trasmitted and locked. Through USB I don't hear any hiss because the locking is instant.
post #2 of 6
I'm not sure if headroom does this, but I do believe there's a maximum sample rate for USB 1.0 (as in the PCM2704). Which isn't the case with optical (correct me if I'm wrong.)

So yes it kinda makes sense (to me at least).. and its probably jitter you hear.. do you use a nice glass cable or a plastic one?
post #3 of 6
Thread Starter 
I think it's plastic...definitely not glass.

All of my music is sampled at 44.1 kHz...would the APX be streaming 16 or 24 bit audio?

Either way I like it more since it isn't resampled.
post #4 of 6
(Hope this isn't considered thread-hijacking, but it seems to be relevant to the issue at hand)

Two questions:

1. Has anyone got any recommendations for a not hugely expensive, glass Toslink to mini cable in a 6 foot length. I can't seem to find one that doesn't use a Toslink to mini adapter at one end instead of a proper mini end.

2. Has anyone done any serious testing of acrylic vs. glass optical attenuation over a 6 foot cable. It's hard for me to believe that over that short a cable length that a well-built acrylic cable degrades the signal enough to be audible.

FYI: I'm currently using the Airport Express Stereo Connection Kit toslink to mini cable which is supplied by Monster (yeah, I know - evil ) but can still return it if I can find a suitable glass replacement.
post #5 of 6
Thread Starter 
AintLDS, I think your best bet is to get a regular 2-meter glass Toslink cable and use a Toslink-to-mini adapter on one end. I think I saw Fry's carry this adapter jack in the store...ebay might have some too.

I heard that 1 meter lengths for plastic were the [most reasonably] longest lengths before signal degradation
post #6 of 6
I would think that use of the adapter would introduce the similar jitter-type issues that you'd be trying to avoid with the straight glass cable. But I'll check into it.

Thanks!
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