Dumb A/V question

[DocSavage44]

Okay, I seem to be missing some basic principle of electronics here, but am stumped.

Here's my issue.

I have one set of powered speakers which I am using for two separate sources. One source is the TV, connected via the headphone output. The second source is AirTunes (Apple's trade name for wireless streaming audio). Both sources use 1/8" stereo plugs.

I figured that since the input for the speakers is a 1/8" stereo, I would simply use a headphone splitter to connect both to the speakers simultaneously. This setup actually works pretty well -- whichever source I'm using at the time is sent to the speakers without any intervention on my part. Pretty sweet.

The problem is that when I have both the AirTunes and the TV inputs plugged in, the signal from the TV drops to about half volume. If I disconnect the AirTunes input from the splitter, the signal from the TV jumps back to normal strength.

What am I doing wrong? Is it because I'm using the setup "backwards"? Do I need to insert some sort of preamp to bring both sources up to normal strength? Would it be better to connect the TV using the audio jack of one of the AV outputs rather than the headphone jack? I like the idea of using the headphone output from the TV because it disables the TV's internal speakers -- very convenient, and I don't have to mess around with selecting sources, etc.

Why does the signal suddenly drop when both sources are connected?

What would work better without a lot of expense and effort?

Also, there is another weird issue -- sometimes the TV input makes a very loud, rhythmic thumping noise that comes out through the speakers -- kind of sounds like some sort of electrical issue, since it's very regular. Disconnecting and reconnecting the TV from the speakers seems to make it go away, but it always comes back eventually, usually right after I turn the TV off. Does this have something to do with the TV's "instant on" circuitry? Is it because the TV's never truly "off"?

Hope someone here can help shed some light on this.

Thanks for your attention,
Doc

 

[markw]

This is one of those "if it hurts when you do that, then don't do that" situations.

You really don't want to combine input sources. Unpredictable things can happen when this is done and this is a textbook example. This has been covered several times here already.

It's got to do with impedance issues, loading down circuits and all sorts of funky technical stuff you wouldn't understand. Heck, I'm not too clear on the technicalities either, but I know it's not a good thng to do. Suffice it to say, don't do it.

Either get a proper switch (and, I'm not too sure I can recall one for 1/8" stereo mini-plugs) or learn to live with one of several inconveniences. Either learn to love these weird sounds or simply switch the plugs as needed and enjoy good, trouble free sounds. My vote is for the latter.

That audio jack on the TV is a good idea but it needs to be fed to an amplifier. Maybe those powered speakers would work as long as it's going to a different electrically separate and switchable input on the speaker.

 

[DocSavage44]

You really don't want to combine input sources. Unpredictable things can happen when this is done and this is a textbook example.

Thought it might be something like that...

This has been covered several times here already.

Sorry, guess I should have searched more thoroughly, but didn't even know what to search for...

It's got to do with impedance issues, loading down circuits and all sorts of funky technical stuff you wouldn't understand.

Well, let's just say it's got to do with all sorts of funky technical stuff I wouldn't understand without a lot of research and explanation that would require more brainpower and time than I would care to invest for this particular issue, and that would be taxing for someone here to explain in detail...

Heck, I'm not too clear on the technicalities either, but I know it's not a good thng to do. Suffice it to say, don't do it.

Okay -- I won't do it! Thanks for the good advice.

Either get a proper switch (and, I'm not too sure I can recall one for 1/8" stereo mini-plugs) or learn to live with one of several inconveniences. Either learn to love these weird sounds or simply switch the plugs as needed and enjoy good, trouble free sounds. My vote is for the latter.

I'm hoping for a solution that won't require plug-switching -- my idea here is to find some sort of solution that's always-on, won't require any switch-flipping or messing about with input or output sources. Would the sort of switch you describe be capable of this sort of "plug-and-forget" operation? If so, I'd be interested in investigating the issue further to see if I can find such a device.

That audio jack on the TV is a good idea but it needs to be fed to an amplifier. Maybe those powered speakers would work as long as it's going to a different electrically separate and switchable input on the speaker.

How about some sort of inline preamp, like a headphone booster? I looked at one of these at the electronics store and wondered if it would work.

Again, thanks for the input, and I'll be interested to see if I can ultimately figure this out.

Cheers,
Doc

 

[DocSavage44]

Would something like this work?

http://www.maplin.co.uk/Module.aspx?ModuleNo=97932&&source=14&doy=search

Doc

 

[markw]

Something LIKE that, yes, Bot not this one.

Would something like this work?

http://www.maplin.co.uk/Module.aspx?ModuleNo=97932&&source=14&doy=search

Doc

If it accepts 1/8" stereo mini plugs instead of RCA plugs like the rest of 'em do it will work, but somehow, I don't think it does.

The problem is that those mini plugs aren't intended to be a common signal transfer medium, like RCA and XLR plugs.

Mini plugs are designed for a terminal, not a transfer, connection, such as a computer or headphone output to one device, and one device only, such as an amplified speaker or a headphone.

Some higher end powered computer speakers allow switching between several inputs but I guess you don't have one of them.

There is a multitude of interconnects, all the same, that you can plug into one of these female output jacks to convert them to RCA plugs to tie into mainline audio components but that's not going to do you any good. you have to go the other way around.

Now, if you can find a converter from a 1/8" stereo mini (female) JACK (not a male plug) to two RCA plugs you'll be in business. So far I haven't been able to find one.

Sometimes in this hobby, andthe workld in general, one has to accept what the rules are and play by them.

Granted, maybe there's a market out there for switches for these divices but, AFAIKT, nobody has seen fit to capatilize on it. Maybe you could be the next Bill Gates.

 

[DocSavage44]

Solved -- I think...

Just bought a simple A/B switch for $15, plus three cables (male 1/8" stereo to L/R phono).

Going to plug one 1/8" into the headphone jack of the TV to one of the inputs on the A/B switch (L/R phono).

The other cable is coming from the Airport 1/8" output to the second phono input on the A/B switch.

The output on the A/B switch is going from the phono plugs to the 1/8" stereo input on the powered speakers.

This ought to work, right? This is what an A/B switch is designed for, unless I'm hopelessly clueless.

I was hoping for a no-fiddle, plug and forget solution, but I guess I can live with hitting the A/B switch to swap sources...

Thanks for the, ahem, "input."

Cheers,
Doc