There is a Page 2 to this Raspberry Pi Forum listing - this is on the second page:
 
http://www.hondosackett.com/yabb/YaBB.pl?num=1415761568
 
You need to open a terminal window in the GUI and type:
 
sudo amixer cset numid=3 n
(where n is: 0 = Auto, 1 = Audio/Headphone Jack, 2 = HDMI)  
 
Then
 
sudo amixer -c 0 cset numid=3 n
(where n is: 0 = Auto, 1 = Audio/Headphone Jack, 2 = HDMI)  
 
Then reboot the R-Pi.

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Since you are using the headphone jack - n = 1
n = 0 only works (rarely) if you had the headphones jack in first. If you are using the HDMI to VGA Adapter, n = 0 will not work.
 
If the R-Pi asks for a User/Password, the standard User/PW is raspberry/pi for the superuser.

It is a Mac Monitor? Mac Monitors (usually) do not have speakers built in but the Mac Mini does have a speaker inside it.
 
If the Mac Mini has external speakers, you should be able to unplug them from the Mac Mini and plug them into the R-Pi.  
 
Though the headphones have 3 connectors on the jack for stereo sound, if you use with 4 - for headphones with a built-in mic - you can get sound-in for the R-Pi. Unfortunately, this is in Mono, not stereo sound input.

Interesting.
 
And it's the same cable from the Mac using to the R-Pi HDMI, it should give sound on the TV.
 
This to me sounds like a ASLI Configuration error in the Config file. I had to go to the Raspberry Pi .org site and found this:
https://www.raspberrypi.org/documentation/configuration/audio-config.md
"IF YOU'RE STILL NOT GETTING SOUND VIA HDMI
 
In some rare cases, it is necessary to edit config.txt to force HDMI mode (as opposed to DVI mode, which does not send sound). You can do this by editing /boot/config.txt and setting hdmi_drive=2, then rebooting for the change to take effect."
 
 
and
https://www.raspberrypi.org/forums/viewtopic.php?t=5062
"What is the display? HDMI or DVI? Is it a computer monitor?
 
My guess is its a computer monitor which reports its preferred mode is a DMT mode. DMT is only well defined in DVI mode, and DVI can't do audio."

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When you do these changes, you need to go to the console and revert the audio selection to either Auto or HDMI (see post above) and reboot the R-Pi. Hopeully it will work from there.

This is a problem with Linux itself and not with Raspberry Pi; as I seen and experienced this with PCs and Linux many times. Its something about the ASLI Driver. (I use Suse and Mandrake Linux on a few PCs with DualBoots with Windows XP, and what works fine with Windows is a struggle with Linux.)
 
My R-Pi's are hooked up to headphones so I use that console command to set the Bootable SD to use headphones.
 
Don't give up on the R-Pi, as far as I know it could be a dead HDMI Audio section. At least you have some experience with them. Expand on your knowledge. At least you have audio through the headphones.
 
Hondo had a similar problem, maybe he will post his fix when he posts here.

Quote from Jeanette on Dec 2^nd, 2015, 7:41pm:

 
You are a brave one if you are going to attempt any soldering on the board. Let me say now, that very difficult even with a surface mounted technology/device hot air gun.
 
(Looking at one of my Model B under a magnifying glass to verify this...)
The HDMI Audio section is from HDMI Port and lead back to the CPU/GPU directly. What's under the CPU/GPU? Who knows. The Audio Jack runs from a separate connection to the CPU/GPU. So the Amplifier is inside the CPU/GPU. Rarely the problem is in the CPU/GPU. It is usually the HDMI Port or the connection to it's port if it is a hardware problem.
 
I still think that this is a software problem, and its in the config file.
 
Somewhere, I need to find it again, there is a config setting and console line input to turn on both the HDMI audio and the headphone audio. Though this link is for a single device output, have you tinkered with the raspi-config? It's in the middle of the page of this link:
https://www.raspberrypi.org/documentation/configuration/audio-config.md
 
ELinux Troubleshooting Wiki has a bit more Raspberry Pi information you could try - I linked it to the sound since the whole page is about issues one may have with the R-Pi and possible solutions. ELinux is a Linux support site and not a Raspberry Pi Site but do support the R-Pi because it uses several forms of Linux.
http://elinux.org/R-Pi_Troubleshooting#Sound
http://elinux.org/R-Pi_Troubleshooting#Sound_does_not_work_with_an_HDMI_monitor
 
BTW - I checked, there is no way to have sound out of Audio Jack and HDMI at the same time.