Why doesn't volume control work on my MacMini?

Mr. Paycheck,

Although that's what I suspected at first thought, I don't buy it. If that's the case, then why do the sliders in the menu bar and iTunes work?

Stranger still, right now I'm listening via Airtunes to my Airport Express, and I can use the slider in iTunes, but not in the menu bar.

I suspect that there is a means of controlling the volume digitally, perhaps by a volume parameter in the TOSLink protocol, but it seems to be implemented unevenly in the different components of software that can control volume, perhaps so they stay out of each others way. When using iTunes, I count 6 different possible ways of controlling volume within the Mac:
--Volume Adjusment in Get Info screen for the song
--ITunes slider
--Menu bar slider
--Keyboard shortcuts
--Apple Remote
--Default slider in control panel

It might be that it's hard to keep these different methods from stepping on each other's toes. I wonder if this is a mini thing, or if other Macs act this way, too.

Thanks for your reply.

This weekend I'll wrestle an analog connection in place and see if I get my various volume controls back.

Thanks for the reply DP,

I think you're right. The "system" sliders seem to govern what the audio hardware supports, while the iTunes sliders manipulate the bits in software. As you say, this can drive up CPU usage. I wonder if it also affects the overall quality of the output at low volumes. I was just hoping the loss of control in optical mode might be one of those little annoyances that might be "fixed" in an Apple software update, someday.

My comment on the TOSLink protocol was rank speculation. With a bit a of Wikipediaing, I found that TOSLink audio is S/PDIF over optical, (but you knew that) and the audio protocol used is AES/EBU. The page for AES/EBU doesn't mention any volume parameters, but there is a channel status bit which yields a 24byte block that can be used in various ways. Since it's an audio spec, if controlling overall volume were one of those common uses, I'd think they'd have mentioned it. Since it has to interface with all kinds and vintages of consumer equipment, there isn't really any room for Apple to get creative here. There is a compressed and uncompressed mode for S/PDIF. Perhaps the compressed mode could allow control of overall volume?

Poking around, a couple of other discoveries:
--Plugging headphones into the audio out of my mini does indeed give me my mini's volume controls back, on all fronts. I like the optical though. Gives me that George Jetson techno rush.
--The menu bar slider does not work in optical mode, as I thought it did, further weakening my argument.

Does anyone know if the system volume can be controlled in optical mode on any Mac? Or any device for that matter?

Hi Boece,

Looks like a neat program, but from the feature sheet, it doesn't seem allow volume control via apple remote. It is a nice example, however, of DPs point of the difference between manipulating bits in software vs. the audio chip.