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Preliminary Review: Headroom Desktop w/Max Module, Max Dac, Stepped Atten., DPS - Page 2

post #16 of 39
9/24/05 at 12:15am
NICE review, your enthusiasm for the unit clearly shows. I had a question, what are ALAC and Airport Express ?
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post #17 of 39
9/24/05 at 12:56am
Thread Starter 
ALAC stands for Apple Lossless Audio Codec, which produces files whose output is bit identical to WAV and AIFF files at around half the size. Airport Express is the wireless 802.11g router that Apple sell, which allows you to stream music from iTunes, and outputs either analogue or digital (optical) output. If you're interested in the Airport Express for audio, look up the stereophile review which is available online. Of course, the analogue output is horrendous, but the optical output is bit accurate.
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post #18 of 39
9/24/05 at 1:00am
i was wondering the same thing. assuming ALAC is apple lossless audio compression. does the airport output the signal via USB or optical out? have you compared sound between optical and USB out from computer. i have a lage digital collection and my current (reads: future iMac purchaser) windows laptop setup only offers USB output. if this monster stack sounds that good via plain 'ol USB i will be damn impressed
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post #19 of 39
9/24/05 at 1:04am
beat me to the punch. so instead of using the wireless output (obviously) you are feeding the desktop max signal via optical out through the airport. very cool....this is getting really expensive.....new headphone rig, new computer for optical capabilities. must stop visiting this site.........yet i cant.
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post #20 of 39
9/24/05 at 1:05am
Thread Starter 
The airport express outputs via a mini optical out. I will test the USB right now and get back to you!
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post #21 of 39
9/24/05 at 1:08am
too cool. thanks man!!
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post #22 of 39
9/24/05 at 1:09am
Thread Starter 
Listening to it through a horrible long USB cable right now. There is the slightest difference, but I honestly can't say it's worse. I had to turn up the stepped attenuator 1 notch with the USB versus the Optical, so I'd venture that my long crappy cable is resulting in some loss of signal. Assuming you use a short, decent cable, I'd say there isn't going to be any difference.

Anyway, what are you worrying about? The iMac that you are about to buy (go on...) has mini optical out as standard, so you won't have to worry about USB in the long term anyway.
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post #23 of 39
9/24/05 at 3:46am
Quote:
Originally Posted by TheSloth
Of course, the analogue output is horrendous
it isn't that bad.
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post #24 of 39
9/24/05 at 2:29pm
Thread Starter 
All I was getting it is that with it's analogue output, the airport express is, in audio terms, a bit of a gimmic, but with digital output can have a rightful place in a very high-end system.
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post #25 of 39
9/24/05 at 2:50pm
Quote:
Originally Posted by TheSloth
Listening to it through a horrible long USB cable right now. There is the slightest difference, but I honestly can't say it's worse. I had to turn up the stepped attenuator 1 notch with the USB versus the Optical, so I'd venture that my long crappy cable is resulting in some loss of signal. Assuming you use a short, decent cable, I'd say there isn't going to be any difference.

Anyway, what are you worrying about? The iMac that you are about to buy (go on...) has mini optical out as standard, so you won't have to worry about USB in the long term anyway.
Strange you say this...because I thought that the Max DAC has its own internal reclocker (like the Benchmark DAC1's "ultralock") to reduce jitter...
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post #26 of 39
9/24/05 at 3:00pm
Thread Starter 
I'm not sure what reclocking has to do with anything here? The USB cable is resulting in significant signal reduction, not jitter introduction, meaning the level at the amp is lower, giving the DAC less signal to work with, resulting in some compression of dynamic range relative to the noise floor (which is of course inaudible in this case), reducing the SNR somewhat. That is nothing to do with the word clock.

I have now tested it with the short cable that comes with the Bithead, and found no difference between the USB and Optical. Only having USB for digital output is certainly not a reason not to get this!
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post #27 of 39
9/24/05 at 6:14pm
Thanks Thesloth, very informative review!!
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post #28 of 39
9/24/05 at 6:20pm
There's no conceivable way that the USB cable could lower the volume; it's running DIGITAL data through there, not analog.

If the USB from the computer is lower volume than the optical from the Airport Express, it's probably because the Airport Express is giving you bit-perfect output, while the computer is going through the OS's master volume control, so is already pre-processing the bit stream.
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post #29 of 39
9/24/05 at 6:34pm
Thread Starter 
Edit: removed.

Well in any case, the USB is close enough. Maybe not perfect, but pretty near.

What determines the volume level of a digital signal then?
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post #30 of 39
9/24/05 at 6:53pm
Quote:
Originally Posted by TheSloth
Edit: removed.

Well in any case, the USB is close enough. Maybe not perfect, but pretty near.

What determines the volume level of a digital signal then?
Judging from mkozlows's post, I think it's windows volume control in your case...ie. I can control the volume of the output signal on my Micro DAC via the volume sliders in itunes. Thus the signal is not bit perfect because my 16/44 ALAC is getting converted to 16/48. In your case, the Max DAC converts everything to 24/192....so since your USB signal is already not bit-perfect, maybe that's one reason why it sounds slightly different than your optical signal? I'm speculating...
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