[kukrisna]

Hey All,

After revisiting DACs and all things digital I came to an assumption that I might not be feeding my DAC correctly.

PREMISE:

A) Source = MacBook Pro

B) two options for digital out:
1) built-in optical out
2) M-Audio Transit

C) two operation systems:
1) Mac OSX where i primarily use Cog
2) WinXP where i primarily use Winamp

D) IC = regular Toslink cable

E) DAC = Presonus Central Station

QUESTIONS:

A) is the built-in optical out bitperfect for all applications in OSX?
B) what's this about the CoreAudio MIDI settings in the Audio MIDI Setup in OSX? i have everything set at 44.1kHz and 16-bit anyway - should it be any different?
C) what's this about the M-Audio USB Audiophile sounding better than the M-Audio Transit even if it's just transporting the same digital signal?
D) what's this about hum and noise unrelated to jitter with the M-Audio Transit?
E) is there an advantage to either the M-Audio Transit or the built-in optical out over the other?
F) in WinXP, i have bitperfect out via Winamp and the proper ASIO configuration to the M-Audio Transit - if i use the built-in optical out, am i correct in believing that i have to tweak things again and that kmixer will be re-enabled and i will have to fix it again to achieve bitperfect out?

PERSONAL STATEMENT:

basically after reading back up on digital signals i became confused again:

- i am unsure if i do have a bitperfect signal on OSX via Cog and the M-Audio Transit - Cog does futz with volume and there's no indication of what the 100% is - if i max out the volume there is a lot of clipping so i think the default is correct though it sounds different than the "correct" sound settings in iTunes 7.5
- i am unsure if the built-in optical out would be better than the M-Audio Transit or vice versa
- i am unsure if the M-Audio Transit does its job well
- i am unsure if in WinXP, if i got rid of the M-Audio Transit, i would have to reconfigure Winamp and re-bypass kmixer if i started using the built-in optical out

REQUEST:

if anyone who really knows about all these things could help to clarify some of my confusion i will be most appreciative

thanks so much!
-keith

 

[kukrisna]

bump

 

[mchang]

Wish I could help you, but my setup is MUCH simpler. I'm not sure it's bit perfect and all that, but it works and sounds great.

Setup 1 in a nutshell:
Intel Mac Mini > USB > 0404 USB. Installed the 0404 software, don't recall changing much. Fired up Audio MIDI Setup. Set Output to 0404 USB. Switched Format to 44100.0 Hz. Fired up iTunes, turned its volume to max. Turned volume on 0404 USB to max. Music bliss. Done.

Setup 2:
Intel Mac Mini > Transmitting wirelessly to Airport Express > Mini Toslink to Optical > 0404 USB. Didn't need to install 0404 software. I don't think I even changed the Audio MIDI Setup from the standard (pre-0404 setup). Turned on selected Airport Express speakers in iTunes. Music bliss again.

I hope my post doesn't seem like a put-down or anything. You may be looking for something completely different than me. I may have my setup done poorly. But I hope to suggest that, with the Mac, it may just not be all that complicated (like Windows world). Good luck!

 

[bigshot]

Optical out is bitperfect in all applications in OSX. Just plug your optical cable into your DAC or amp and you are all set. Can't tell you about windows.

See ya
Steve

 

[krmathis]

Beware that its only bit-perfect if the playback software don't alter the audio stream in any way.
Meaning:
* Volume at 100%, not 99.9% or whatever.
* No EQ.
* No Replay Gain.
* Etc..

 

[cconnaker]

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif Optical out is bitperfect in all applications in OSX. Just plug your optical cable into your DAC or amp and you are all set. Can't tell you about windows. See ya Steve

I would be careful with this statement. While it is probably possible for "all" applications to be bit perfect, it is 100% possible for all applications to NOT be bit perfect depending on how the app is configured.

 

[bigshot]

I guess I assume that if you're applying processing, you know you're applying processing. Perhaps a clearer way of saying it is, the hardware itself is capable of bitperfect output from any program.

See ya
Steve

 

[kukrisna]

hey all,

thanks for the replies

im still unsure about anything related to the M-Audio Transit, Cog, and CoreAudio - if anyone knows more about my issues relating to those specific things that i mentioned in the first post, i'd be glad to hear what you've to say

 

[kukrisna]

bump

 

[kukrisna]

final bump then i guess im on my own

 

[grawk]

Quote:

Originally Posted by kukrisna /img/forum/go_quote.gif QUESTIONS: A) is the built-in optical out bitperfect for all applications in OSX?

As other said, yes, core audio doesn't change the bits the application sends it. So from that perspective it's always bit perfect.

Quote:

B) what's this about the CoreAudio MIDI settings in the Audio MIDI Setup in OSX? i have everything set at 44.1kHz and 16-bit anyway - should it be any different?

Only if you're sending it something that was sourced at a different bitrate. Generally you'll want to send it 44.1/16 since that's what cds are.
Quote:

C) what's this about the M-Audio USB Audiophile sounding better than the M-Audio Transit even if it's just transporting the same digital signal? D) what's this about hum and noise unrelated to jitter with the M-Audio Transit?

These will all be referring to analog outs not digital. There won't be a difference between transit and usb audiophile's digital output, excluding jitter. Quote:

E) is there an advantage to either the M-Audio Transit or the built-in optical out over the other?

Some people don't like the optical mini connector. Quote:

F) in WinXP, i have bitperfect out via Winamp and the proper ASIO configuration to the M-Audio Transit - if i use the built-in optical out, am i correct in believing that i have to tweak things again and that kmixer will be re-enabled and i will have to fix it again to achieve bitperfect out?

can't help you there

 

[kukrisna]

grawk! thank you so much for answering my questions - that just about answers everything i've had a question about (save the individual players - though after listening to Cog and iTunes again on a sine wav and looking at the level on my presonus i think they're outputting correctly and it was just paranoia before)

thanks again!!

 

[flohmann]

One other variable to consider: jitter.

While the optical output on both the MacBook and Airport Express are capable of bit transparent output, jitter can still make an audible difference. I was just doing some comparisons last week, and found that the same songs sounded obviously better straight off my CD than it did from hard drive over Airport Express, even where fed to the same DAC (Sennheiser 650, Blockhead, Mark Levinson 390S).

I'm trying to buy a Genesis Digital Lens to insert between the Airport Express and the DAC to see what difference it makes, as it principally targets jitter.

Stereophile included jitter measurements in its review of the Airport Express (230 picoseconds), but I've never seen jitter measurements from a MacBook's optical output. Would be interesting to measure that.

 

[kukrisna]

Quote:

Originally Posted by flohmann /img/forum/go_quote.gif One other variable to consider: jitter. While the optical output on both the MacBook and Airport Express are capable of bit transparent output, jitter can still make an audible difference. I was just doing some comparisons last week, and found that the same songs sounded obviously better straight off my CD than it did from hard drive over Airport Express, even where fed to the same DAC (Sennheiser 650, Blockhead, Mark Levinson 390S). I'm trying to buy a Genesis Digital Lens to insert between the Airport Express and the DAC to see what difference it makes, as it principally targets jitter. Stereophile included jitter measurements in its review of the Airport Express (230 picoseconds), but I've never seen jitter measurements from a MacBook's optical output. Would be interesting to measure that.

well i plan to upgrade to a decent USB DAC that users here have reported good results in terms of jitter compensation (i.e. from benchmark or bel canto) - in the future of course - strapped for cash ATM

 

[bigshot]

Jitter is inaudible at the rates you would get from the optical output of a mac.

See ya
Steve