So, I installed "Radio Tray" to get some good music playing while I work...

But I noticed that the audio keeps playing through the iMac's built-in speakers, even when I have my pair of external, powered speakers connected to the line-out jack and turned on.

Here's how it behaved in OSX when I'm playing audio... like in iTunes for example:

• iMac is on, external speakers not connected to iMac... = sound plays through built-in speakers (good).
• iMac is on, external speakers plugged in but turned off... = no sound (good).
• iMac is on, external speakers plugged in and turned on... = sound plays through the external speakers only (good).

MintPPC seems to play sound through my built-in speakers all the time and doesn't obey my desire to have them muted but only play sound through my external speakers.

Also, consider this too...:

• Both my iMac and external speakers are off. The external speakers are plugged into the iMac.
• I boot my iMac only and keep the speakers turned off.
• When I reach the desktop and play any kind of audio, it only plays through the internal speakers.

On the other hand...:

• Both my iMac and external speakers are off. The external speakers are plugged into the iMac.
• I boot my iMac and speakers on at the same time.
• Audio plays through both the internal and external speakers... which is ANNOYING!

When I go into the volume settings, I try to mute the internal speakers... but it mutes everything.... INCLUDING my external speakers... and I can't get audio playing through the external speakers unless I unmute the internal speakers! (NOT GOOD!)

Is there a way to correct this?

I almost forgot to mention that this was also the case in MintPPC 9.x as well.

Did you try gnome-alsamixer to mute one channel over the other ?

Yes... i did. Sometimes I can mute the internal speakers and get audio to play through the external speakers that way... but sometimes it doesn't even work! And there are times when the volume sliders don't even behave properly...

...like when I slide the volume all the way down for the internal speakers, they still play the audio!

On other mainstream OSes, if you slide the volume all the way down for one channel, the mixer usually interprets that condition as a situation where you want that particular channel to be muted. And even from a muted position, if you slide the volume back up, the sound is no longer muted.... and it respects the actual volume setting that the slider is set to.

I don't know if this thing is a bug specific to MintPPC, to Debian, or just to the gnome-alsamixer...

This is not MintPPC specific. You have to understand that MintPPC is nothing more than plain Debian with some tricks. The tricks being some graphical user interface and some added stuff related to PPC. Maybe you need different sound modules for ALSA. You can experiment a bit with the page written by oswald kielso, another dedicated PPC user.

http://oswaldkelso.blogspot.nl/2010/10/ ... werpc.html

Your external speakers are probably considered "headphones" to the OS, so I'd try adjusting that slider as well.