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PowerBook G4 + Apple Express + iTunes +? to analog

My goal: Optimize my wireless Mac system to rival the quality of my Arcam CD192 CD player (running into an analog Arcam amp).

This isn't (yet) a question about brand recommendations (e.g., external DACs). At this point I simply need some help understanding how the system should be configured and what types of items I have to buy. I've already decided not to go with SlimServer or Sonos because I prefer to use my existing Mac computers + iTunes + Airport system as my source.

Current setup:

Office/server room:
1. Power Mac G5 dual 2.5
2. Lacie 500GB external drive (holds the Apple Lossless files)
3. iTunes running on the G5 ("iTunes Music Sharing" enabled)
4. Airport Express (802.11g) used as base station/Internet router

Listening room:
1. PowerBook G4 (next to listening chair, with iTunes channeling the shared playlist from the G5)
2. Mac out: analog 3.5mm headphone jack + RCA adapter
3. Amp in: analog RCA jacks on Arcam FMJ A32 + Dynaudio Audience 72 speakers

The audio quality with this set up actually is quite good on first blush. A/B comparisons with the Arcam CD192 are difficult, partly because the Mac source is about 5% lower in volume. I suspect that the Mac source is slightly less "authoritative" or "robust" than the CD player, but because I have to increase the volume of the Mac source to match the volume of the CD player, I can't be entirely objective. I also suspect that the Mac source might be somewhat fatiguing, but this could be due to the higher than normal volumes I used for A/B testing. So, while I'm not entirely convinced I actually need more components, I'll accept the conventional wisdom that an external DAC would overcome any deficiencies, fatiguing or jitter in the Mac source.

My questions:

If I buy an external DAC,

1. Must I buy an additional Apple Express for the listening room, or can I simply hook up the DAC to the PowerBook? (I would need a 24 foot cable to get from the PowerBook to the DAC/Arcam amp. An Airport Express could be located about 3 feet from the DAC/Arcam.)

2. Which type of DAC input -- USB, Firewire, or optical -- is recommended for this setup? Does the answer depend on distance from the digital source (question #1) or on the particular qualities of each connection? Or both?

3. Would I hear an improvement with only the DAC (versus analog headphone jack), or is an anti-jitter box recommended as well?

4. Must I change the way I use iTunes? For example, do I have to make the PowerBook G4 the "iTunes master," so that it directly accesses the library on the Lacie HD over the wireless network? Or is my current "shared playlist" method (using my G5 as the master) OK?

I realize that questions #2 and #3 are probably the most contentious and have already been asked on this forum, so I apologize for the repetition, but haven't seen a concise discussion of the issue of distance. Perhaps I missed it. Feel free to point me to other discussions as needed. Thank you!
syncrasy
syncrasy OP
14 posts
 
Steve,

Thanks for your response. I'm a newbie to digital audiophile-dom, so could you please clarify a couple basic concepts for me...

1. Are you saying Airport Express's optical *and* analog outputs are jittery? Does AE jitter come into play if I'm using my AE simply for wireless transmission of data?
2. When you say that the DACs in computers are noisy, are you referring to obvious background noise (i.e., static) in the signal, or more subtle noise (i.e., distortion) in the music? (I don't hear any obvious noise or distortion in the analog output of my PowerBook, but perhaps my ears aren't trained to hear it.)

Thanks!
audioengr
3,282 posts
 
Syncrasy wrote:

"Are you saying Airport Express's optical *and* analog outputs are jittery? Does AE jitter come into play if I'm using my AE simply for wireless transmission of data?"

Yes, both are very jittery. The clock in the AE is a relatively high-jitter oscillator.

The analog outs are poor simply because its a really cheap D/A implementation. For wireless transmission of data to a printer etc., real time clocking is not an issue. There is the data and then there is the timing with audio streaming. Timing jitter is a non-issue with data transfers other than audio such as to a printer.

"When you say that the DACs in computers are noisy, are you referring to obvious background noise (i.e., static) in the signal, or more subtle noise (i.e., distortion) in the music?"

Both. There is sibilance (audible HF noise)in the analog signal due to noisy switching power supplies (electrical noise), poor power decoupling and poor signal paths. There is distortion due to all kinds of things, including poor D/A filter caps, poor coupling caps (dielectric absorption), poor power delivery to the D/A chip etc. It's just a really cheesy environment for a D/A chip and op-amps, which are very sensitive to power, PC board design and ancillary discrete parts.

Once you audition a well-designed DAC, you will know what I'm talking about. There are many levels to audio quality. We are obviously in totally different realms you and I if you dont hear gross distortion and noise from the analog outs of a laptop. It does not take a trained ear to hear the difference. It is just a matter of experiencing a resolving system.

Steve N.
Empirical Audio
ecktor
1 posts
 
I've found this thread interesting, and I hope I'm not hijacking the thread. But I have a question about a "reclocker" between the A/E and a DAC.

Audioengr: would you mind making a recommendation for a reclocker? I'm enough of a newbie that I'm not even sure where to look for such an animal.

I just this morning received the remaining (minus a reclocker) pieces needed to set up my music server: CD library on iMac ==> Airport express ==> Digital out via digital out on A/E to TOSLINK cable ==> Musical Fidelity DAC ==> Denon integrated amp...

Any help on the reclocker would be appreciated.

Thanks in advance.

Eric
syncrasy OP
14 posts
 
Steve, thanks for the additional information. I have another follow-up question.

You said:
The ideal scenerio is the AE driving some kind of reclocker and then outputting I2S bus to a good DAC. This will achieve the lowest jitter and the best analog quality, assuming a good clock in the reclocker and good analog design in the DAC.

Next best would be AE driving some kind of reclocker outputting S/PDIF coax to a DAC.

Third best would be AE to a DAC with upsampling to reduce jitter to some extent.

Where in this hierarchy would you place the following setup:
AE (wirelessly) to PowerBook to (via Firewire or USB) reclocker to DAC to Arcam amp?

This is the setup I'm considering. (Hence my question about potential jitter for wireless data--I did mean streaming audio data, not just plain data.)

Thanks!
syncrasy OP
14 posts
 
Steve, just to clarify...

I said:

Where in this hierarchy would you place the following setup:
AE (wirelessly) to PowerBook to (via Firewire or USB) reclocker to DAC to Arcam amp?

The source of the music files is my PowerMac G5/Lacie Firewire hard drive (transmitted by the AE to the laptop).
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