4/2 Line router (audio) and 2/1 Line router (audio)

[bfish]

Hi,

I'm a newbie. I've worked witha breadboard and sodering iron. The problem I'm trying to solve is this:

I've made a bag that holds 3 mp3 players and a CD player. It also holds 2 cell phones. I want a switch (preferably passive) That lets me send any one of the audio devices to either of two headphones. I also want to be able to switch the cell phones to one headset/mic. Thus, I see two "routers" (I'm a programmer, sorry). One router is 4/2 to send any of the 4 audio devices to either of two headphones. The other router is 2/1 to send either of the two cell phones to one headphone/mic.

I'd like to keep this light and small so that it will fit unobtrusevly in the bag and I don't want it to be powered unless it has to be so that I don't have to fiddle with batteries.

My initial thought was that I'd just build a box that switched four input jacks to an output and then split the output with another switch. A friend said that I'd get awful degredation, feedback, etc. He said I'd need to add resistors, but I have no idea where. When I looked around to buy one of these they were exceedingly rare and quite costly. So...are they costly because they are ridiculously complicated or because nobody else is so silly as to carry so much duplicate crap around?

In a dream world, I'd have volume controls at each input and an amplifier at the output (of course, I realize that requires power). All of this, however, is beyond me.

Can anyone help with a diagram that I could put on a simple breadboard and test? If I have to power it, I'd like to do it with rechargeable AAA or AA batteries if that is possible.

Thanks for the help.

 

[hjames]

Is having two headphone on the same audio source is a requirement? Everything you described is can just be done with some nice passive switches, unless you have multiple loads on a source. Then it'll cause odd things if the headphones are of different impedances and in general, you can expect your volume control to go nuts.

As for the supposed audio degradation, it probably wouldn't be noticible.
Wander over here for some switches:

https://www.mouser.com/index.cfm?handler=catalog
Start looking at page 1276

For switching the headphones, I'd recommend a "3 pole, 4 position" minimum switch. Actually, since these are pretty big rotary switches, you can probably just get a "3 pole 8 position" and have half the positions for one headphone, and the other half for the other one.

General cautions: When dealing with headphone outputs from portable devices, you should probably switch all 3 wires - there's times when the common line *isn't* ground, and it'll show up in weird ways like while charging or the like.

Finding the plug for the cellphones is likely to be painful - they tend to have 4 contacts on some very dinky connector....

James

 

[bfish]

Is having two headphone on the same audio source is a requirement?

No, it is an either/or arrangement.

you can probably just get a "3 pole 8 position" and have half the positions for one headphone, and the other half for the other one.

Thank you...this is the switch I'll try to find.

 

[bfish]

should I be selecting a shorting or non-shorting switch? My thinking is a non-shorting switch. I'm looking at mouser part #690-C4D0312N-A which is a 3 pole switch that allows 2-12 positions (configurable). Fairly expensive, but not horrible since I only need one...

 

[hjames]

Yep, break-before-make/non-shorting is a good idea.

That one looks reasonable. Incidentally, the other ("left field") idea I had was to use a pile of reed switches. They're sensitive to magnetic fields, and essentially you'd be able to "switch" channels by simply moving a magnet around. It's defintely more complicated and not at all "practical", but it would make a pretty cool gimmick. Mouser carries them at 50 cents each, but you'd need a pretty ludicrous number of them, and some oddball magnetic shielding and the wiring would be...amusing.