Audio 'Y' adapter to combine sources - am I overthinking this?

July 31, 2008 9:31 AM

I want to simultaneously connect the outputs of both an iPod and an iPhone to the same input - will a simple Y adapter suffice?

I have an idea that using a plain vanilla Y adapter, in addition to supplying the audio signal to the destination input, would also allow the audio from one device to creep up the wire to the other, which it obviously was not designed to accept. We're probably talking about some pretty small voltages here, but should I install some diodes or something on one side to avoid audio injection?

If so, what specs would you recommend, and do I need one for each channel (left and right)?

posted by DandyRandy to technology (6 comments total)

I'm really not sure what it'll do to an iPod, but I probably wouldn't try it. It'll lead to an impedance mismatch, and I'm not sure how well the iPod/iPhone's output circuits deal with various loads. Probably you'd just get distortion, but I wouldn't try it, because the solution is fairly simple.

What you really want is a little stereo mixer. That will let you hook up both devices (and adjust the volume of each independently), and mix the signals together into the output, which you can send to your amplifier/stereo/recorder/whatever.

If that's overkill or if you're on a very tight budget, you can build a passive mixing circuit that will eliminate the mismatch.
posted by Kadin2048 at 9:45 AM on July 31, 2008

That stereo mixer is overkill. Too many moving parts, too many places for a crappy Radio Shack mixer to dirty up your sound. You could make this RCA switcher extremely easily, and it wouldn't have to have quite that many inputs. Add a pair of RCA-->1/8th stereo cables, and you're all set. Or, if you need both sources at the same time, that passive mixer should be fine.
posted by god hates math at 9:56 AM on July 31, 2008

The easiest way to do it is to build a signal combiner. You just need to connect each jack to each other with a couple of 10K resistors.

For example, here is one that I made to mix down two mono signals and a stereo signal. Just directly connect the grounds from each jack, and connect the signals with 10K resistors (really, any value around 10K will work).

You don't want diodes, as diodes will act as a rectifier, distorting the alternating voltage audio signal.
posted by Bahro at 10:00 AM on July 31, 2008

I suppose I should have mentioned this is for a portable car installation - looks like the signal combiner would be the easiest, but I still see a path (although attenuated) between the outputs. This is not a big problem?
posted by DandyRandy at 11:09 AM on July 31, 2008

Nope, shouldn't be a problem. Here is where I originally found my information.
posted by Bahro at 11:27 AM on July 31, 2008

I'm no electrical engineer, I would have thought that seeing as you're only ever realisticly going to be using one or the other of the iPod/iPhone, you shouldn't have to worry about interference or any of that fancy electrical mumbo jumbo ;)

And anecdotally, I use a simple Y-splitter to plug my Xbox 360 and PC audio through the same set of speakers and have had absolutely no problems with it, save for a very small loss of amplitude from the PC side (although curiously not from the 360).
posted by jon4009 at 1:29 PM on July 31, 2008