Multiple audio outputs into one input?

[Opus4]

I've got what I hope is a simple question... I've got a PC that is audio input challenged, in the sense that there is a single minijack input. Is there any problem using a Y adapter to send 2 outputs to that single input? I can obviously use a Y adapter to split output, but I don't know if going the other direction could cause any problems for the 2 output devices.

I'm no expert at these types of connections, so I don't even know whether a microphone input could be used as another general purpose input.

- Andy

[ke6guj]

I don't see why not. Just make sure you only have 1 incoming signal on at a time. Shouldn't be an issue unles one of your devices output doesn't shut down completely and leaves some spurious noise signals in the line.

I did something similar back in my VCR days. I had a TV that had a s-video and RCA video input that shared RCA audio inputs. I hooked up 1 vcr's video to the s-vid and the other's to the RCA video. I Y'ed the audio connections together and made sure only one VCR was on at a time when I wanted to watch a recording.

[Opus4]

I wasn't worried about sending both signals into the same input, but I read somewhere that it wasn't good for the output lines to have something coming back into them. I read this on the internet & of course you can't trust everything on the internet... but I don't know enough about the subject to know whether it was BS or valid, even though I saw it mentioned in multiple places.

I'm no longer worried much about that part because I determined I can use the microphone input & configure it as another line in, so now I'm just curious about it.

- Andy

[Conejo]

Hey Opus,

Most 'electronic engineers' cringe when they see the reverse Y-adapter used to combine to sources, even if only one source is used at a time. Though it should be fine with 'line-level' equipment. Very little chance of overloading the output stage.

If you take a look at the schematics for most 'mixers' they too combine all the wires together, just adding a 4K or 10K Resister to 'pad' or 'buffer' the signals from each other.


[image Copyright Tomi Engdahl 1997]

The circuit diagram above has potentiometers (variable resisters) to vary each input signal level but they could be left out -- So there'd be just the bottom resistor to diswade the signal from traveling back up another input.

Some examples of where the Y-adapters shouldn't be used are:
1) attempt to 'mix' Left and Right stereo signals to mono; you'll just wind up with weird sound levels (sound sent to L or R only stays at normal levels, but the same sound sent to both L & R become double loud).

2) used to split or combine amplified speaker outputs; the mismatch could lead to a blown output channel.

[Opus4]

Thanks for the info -- I had a suspicion there might be an issue connecting things that way, thus my Google search & forum post, so now I know for certain to avoid that in the future.

- Andy