iTunes: dynamics, midrange gone 'til restarted

Did you check the MIDI settings to see if they were set to what you wanted at the point you encountered this problem?

I haven't configured the MIDI settings in any way. I'm using the Mac's output as the front end for my 2 channel stereo system. It appeared that the only thing I might want to configure would be the audio output, and it's already set for 2 channel speakers (my system is two channels). I'm not really inputting anything into the Mac as a music source....I just use it's dvd drive for ripping. If I want to play a disc, I use my external dvd player into my pre-amp, etc.
What settings should I consider changing, in your opinion?
One thing I can do, I suppose, is record the currently employed default settings, then see if they're different when I re-encounter the problem.
Thoughts?

Yeah, the exact same thing happens to me. And you're absolutely right, the difference isn't subtle at all.

I thought I was going nuts, until one of my very "non-audiophile" friends (she rolls her eyes constantly) noticed.

I've never noticed this happening until recently. I'm wondering if it is because of iTunes 8.

I'm streaming into an airport express though, and thought the problem lay with the AEx or my router. Guess not. The sound improves when I unplug/re-plug my airport express.

I know common wisdom was not to use the itunes volume control and leave it at max (change volume on preamp/amp) but I've never noticed a problem before doing it on itunes. Now it experiences an instant degradation of sonics as soon as I do it.

So your work-around is simply to re-start itunes? What happens if you don't shut down your Mac-mini or itunes but simply stop playing music for awhile?

Sorry I can't be more help. I tried posting a similar question on a computer audiophile forum, but no answers. If you figure something out, let me know. It's a really annoying problem.

Elf73, I have my Mini "hardwired" to the DAC with a USB cable, probably as you deduced. I wonder if reconnecting the Airport changes a setting or such in the iTunes program? If I restart the iTunes, everything is ok.
I probably should report this to Apple. I just wanted to make sure I wasn't the only one with the problem.
It'll give you a heart attack if you don't remember it in association with the installation of new hardware!

Yeah it is very disconcerting...

I have checked and my settings haven't changed. And for me, with streaming to the AEx, I don't think the AudioMidi settings even factor in.

For you since you have it hardwired, it may be a different story.

I have mine connected to from the AEx into a DAC through a toslink cable.

I'm almost positive, from your description, we're encountering the same problem. The sound completely recesses at some point.

Once you re-start itunes, does it remain stable. That is, the sound stays to your liking?

I've read something Benchmark put out about the sampling being done either through itunes or the operating system, something to do with "coreaudio", or SRC (Sample Rate Conversion), "truncated word-length". I didn't fully understand it at the time (I'll blame it on jet-lag)...

I couldn't find the article, but here is one that may help. At least, it'll help with your AudioMidi setup:

http://extra.benchmarkmedia.com/wiki/index.php/ITunes-QuickTime_for_Mac_-_Setup_Guide

Found it:

http://www.benchmarkmedia.com/feedback/issues/122007.php

I'll re-read it, and if you can make sense of it in practical terms.. let me know.