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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

Showing 5 responses by audioengr

audioengr
3,282 posts
 
To get a stellar result with AE, you must address two things: first the jitter issue - AE is one of the worst sources for jitter, and then the DAC issue. Forget about using the DAC's in the Computers or these end-point devices. They are not good quality. Very noisy and not dynamic for reasons that I will be happy to explain. Use the digital output instead.

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.

Steve N.
Empirical Audio
audioengr
3,282 posts
 
Your new proposed setup will work fine.

Apple-lossess is fine too, although there are some CODEC artifacts, so It's not perfect. It is the best thing to do with Mac. You could also look at AIFF.

Steve N.
Empirical Audio
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
audioengr
3,282 posts
 
Syncrasy - the connections would be:

Powerbook -> WiFi -> AE -> Toslink -> Reclocker -> S/PDIF coax -> DAC -> analog -> Arcam amp

Steve N.
audioengr
3,282 posts
 
Syncrasy - why do you need the AE?

Networked audio, particularly if you are only doing 44.1kHz sample-rate will be more trouble-free than USB. I would only do USB if you must have 24/96 capability. USB tends to hog system resources. It can work great for audio, but if you are using an AE already, why not use it to stream the audio data?

Also, if you are using a reclocker after the laptop, why do you need Firewire/USB? Just run Toslink directly into the reclocker from the laptop. This avoids many of the issues with the shared USB and firewire buses.

Steve N.
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