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My PC Audio Question Journey

I finally took the step of getting an external DAC (Maverick D2) allowing me to stream iTunes from my computer via an Apple TV. So far, I have only used a PC, but purchased a Macbook Pro over the weekend that will become the primary computer in the near future.

My system is the following:
Computer with iTunes (Apple Lossless)
Apple TV
Maverick D2 DAC (tube and solid state outputs)
Yaqin MC-30L amplifier
Focal 836v speakers

As a baseline, I have been unable to tell a difference between the solid state DAC output and my Elite SACD player. I am also aware that the Apple TV streams 48 kHz instead of 44.1 kHz which, in theory, is weakness in the digital signal.

Overall, I'm satisfied with my current sound, but I could be convinced to upgrade the Apple TV to an Airport Express and also to use a parallel software that works with iTunes (as long as Airplay is still supported) if I was convinced that an objective improvement could be expected in my system.

There's several layers to the discussion so I thought I'd ask my questions one at a time in an effort to keep things focused.

TOPIC 1:
The goal when ripping a CD is to create a "bit perfect" digital copy on the hard drive. Should it be expected that using iTunes will achieve this goal? If not, is there an objective way to validate that another software performs this step better? Is the primary reason that most recommendations are to not use Apple Lossless vs. other lossless formats is because it is propriatary to Apple making it the most limiting format in the future?
mceljo

Showing 6 responses by kijanki

kijanki's avatar
kijanki
4,410 posts
 
I use Itunes with Airport Express for playback but MAX on the Mac for ripping. Conversion 44.1 to 48kHz on Apple TV is audible, according to few threads here but Airport Express is a little bit jittery. Is not an issue for me (with Benchmark DAC1) but you might look for jitter suppressing (reclocking)DAC or stand alone reclocker.

https://wyred4sound.com/products/digital-converters/remedy-reclocker

I'm not sure what format is used with Apple TV but Airport Express uses, AFAIK, ALAC. Storing files in different format would force computer to do additional conversion.
kijanki's avatar
kijanki
4,410 posts
 
Airport Express is connected by Wi-Fi and as such does not receive in real
time. Itunes/Airplay does not transmit PCM. Computer transmits ALAC data
in packets that are stored in AE in a buffer containing about few seconds of
music. Timing is added from internal AE clock (resulting in 258ps peak-
peak jitter) and S/Pdif PCM stream is created. In order to use format
different than ALAC computer would have to make on the fly conversion
that would not affect the sound since transmitted is data without any
timing.

read this discussion on APPLE support forum:

tstart=0>https://discussions.apple.com/thread/3339297?tstart=0
kijanki's avatar
kijanki
4,410 posts
 
That's the beauty of the network bridge - computer, playback program etc make no difference since no timing is involved. PCM stream like S/Pdif coming directly from computer to DAC can be affected since computer creates timing.

Timing on the DAC side is recreated with new clock. AE is a little jittery and limitted to 16/44.1 but there are better choices. Logitech stopped making Squeezebox Touch but Sonos makes Wi-Fi Bridge.
kijanki's avatar
kijanki
4,410 posts
 
Mcelio, Stereophile measured 258ps jitter on Toslink output. Jitter
artifacts on analog output corresponded to about 2400ps jitter.

Little jittery is very loose term. To me 258ps is still OK (requires some
suppression) while 2400ps is pretty bad. I remember reading that 50ps is
already audible and very good clocks are much better than that.

Jitter is a system thing - even 1ps AE would still suffer higher jitter
created by system noise since Toslink transitions are pretty slow. Coax
output would be faster but then you have to pay attention to characteristic
impedance of the cable and impedance matching. I have both AE and
DAC plugged into power conditioner to avoid any system noise that could
possibly come from mains. In addition Benchmark DAC1 has pretty good
jitter suppression. Benchmark DAC1 in comparison to CDP (Cambridge
CD4SE) sounded too clean at first. Many people perceive jitter also as
poor image and harshness, perhaps because noise screws-up everything.

My AE is first generation (model A1264), perhaps I should upgrade to
second generation that has lower jitter (but not always) - discussion
below:

[url]http://www.computeraudiophile.com/content/466-measurements-
first-and-second-generation-apple-airport-express/[/url]

Interesting review of latest AE:
[url]
http://kenrockwell.com/apple/airport-express-audio-quality-2014.htm
[/url]
kijanki's avatar
kijanki
4,410 posts
 
Mceljo, Whatever lossless format you choose it will be converted to Apple compressed lossless (ALAC) anyway, before sending to AE. As long as it is bit perfect it is data - no timing difference (that could affect sound).
kijanki's avatar
kijanki
4,410 posts
 
That's what I concluded and ripped everything into ALAC. Batch converting to other format is also possible if necessary.
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