Output switch for iMac, how to fool the imac into thinking nothing is plugged in?

[Jack Isidore]

I have long wanted to make a little switch box for my imac (first aluminum generation, imac7,1), which would have a line in going from the imac headphone out, and two output jacks, one going to my amp, and the other open for headphones. My motivation is not having to reach around a cramped setup to unplug and plug all the time when I want to switch speakers. The problem is, the imac mutes the imac speakers if you have anything plugged into the headphone out jack. So, I would still have to unplug my switch, if I wanted to switch from headphones or amp to imac speakers. I think I tried plugging in an old wire from broken headphones (open circuit) and it still recognized as something plugged in.

 

Does anyone have an idea how the imac determines if something is plugged in, and how I might be able to fool it with a circuit of some sort? Even better if you can point me to a thread that covers this, I couldn't find one.

 

[AudioDoctor]

You could I guess even come up with a script to do that with a mouse click or something.

 

[Jack Isidore]

I had found that possible solution on another forum, although when I have the amp plugged in, the only option is the headphones, on the drop down. I tried under the preference pane for sound output, as well as the audio midi setup utility.

 

I just read somewhere something about normalled jacks, that short out when nothing is plugged in. Maybe that is what these do. In that case, instead of an open circuit, a closed circuit may do what I want. I can't find that old headphone plug, if I can find it, I'll give it a quick shot. Intuitively, it seems like this wouldn't be the case though. I mean, why wouldn't they have it mute it when it isn't shorted, since when there is nothing plugged in, it is an open circuit. Instead, they have the jack short itself when there is nothing plugged in?

 

[Audio_ELF]

Try SoundSource from http://www.rogueamoeba.com/freebies/

 

Eloise

 

[AudioDoctor]

in that case, I am out of ideas. Sorry.

 

[Jack Isidore]

Ah, this looks promising. I'll give it a shot later, thanks!

 

[Jack Isidore]

I tried Sound source, but unfortunately, it only gives me the same options as the preference pane (only headphones when headphones are plugged in).

 

Bummer...

 

[4est]

This effect happens when using a toslink in the headphone jack as well. If it does short using the plug, it would be near the tip, as the rest of my plug is plastic. IIRC, older headphone jacks would break the connection to the main out as a function of plug insertion.

 

[fever]

apple uses switchable jack connectors. the spring loaded switch is closed (i.e. bypassed) if no jack is inserted. as soon as a jack is inserted, the contacts are pressed apart and the switch is open (i.e. the signal goes to the jack). the only work around is to open the i-mac and bypass the switch by soldering a wire between the contacts (i.e. the jack still mechanically but no longer electrically opens the switch). might be a bit tricky though. then use SoundSource to switch between the internal speakers and external.

 

the other option would be a cheap USB dac/headphone/line amp.

 

-fever (new here; this is my first post. hi everyone btw...)

 

[Jack Isidore]

I see, so it's mechanical > not good for my purposes. Although I have opened up the iMac to replace the hard drive, I don't think I want to go messing around to that extent.

 

I know there is no shortage of expensive USB DACs, but I'll look around for a cheap one.

 

Thanks!

 

[Audio_ELF]

I think the cheap USB DAC is probably the answer to your problem... With the added advantage that it will probably improve the SQ over the headphone out to your amp.

 

A good starter option may be the Aune Mini DAC available (from China) via eBay; or a Nuforce, Firestone or similar DAC. The other advantage of these is they have a proper headphone amp built in.

 

Eloise

 

[wgscott]

I have this:

 

http://www.turtlebeach.com/products/sound-cards/audio-advantage-micro-ii.aspx

 

It is a USB to optical and USB to analog mini adapter. Limited to 16/44.1, but it sounds fine with my Zeppelin.

 

Then you can option-click the menu bar speaker icon thingie to switch back and forth between this and built-in (speakers).

 

 

[Jack Isidore]

Thanks, the price sure is right.

 

BTW, love the avatar, we have "On the Effectiveness of Aluminium Foil Helmets" posted in the office at work.