Can +5v from a smart phone mic jack damage an Aux Send?

Special Interest Groups Recording Equipment
1

I recently tried to use a computer headset microphone to record into a mixer. After getting tons of help from the guys on here, learning A LOT and spending lots of money and time, however, I decided I had reached the point of diminishing returns and had to give up.

Ultimately my goal was to be able to use Aux Send to route the signal from several headset mics through the mixer and to a phone and record the mix as an interview (using a headphone amp to send the mix to the headsets).

I got a couple real microphones and stands and that problem was solved. I decided to try to use my android as the phone. It, of course, has only one jack so I wondered how I was going to “give” it the mixed signal from my board and “get” the caller’s voice out of one hole. That’s when I found this cable:

http://www.startech.com/Cables/Audio-Video/Audio-Cables/35mm-4-Position-to-2x-3-osition-35mm-Headset-Splitter-Adapter-Male-to-Female~MUYHSMFF

It splits the 4 pin jack into “mic in” and “headphone out”.

The pinout on the 4 pin plug is:
Tip: Left
R1: Right
R2: Ground
Sleeve: Mic
(Notice no “mic power +5v” pin)

So my question is, where does the cheap headset mic that comes with every smart phone get it’s power if all 4 pins are busy? (and none are designated “Power”?)

I don’t know for sure (I definitely looked) but I assume this splitter cable goes:

Headphone out jack:
left, right, ground (TRS)

Mic in jack:
mic signal, ground (TS)

I know that the pinout for a computer mic is:
mic signal, +5v, ground (TRS)

My first thought was that maybe there was no power on any pin so I tried a different headset mic (the one I had tried to use with the mixer) and it worked (with lots of noise) - which meant it was getting power from somewhere.

That meant that the power must be sent up through the “mic” (#4) pin. Because it wouldn’t be sent up though the “ground”. Can that be right?

My other question then is this:
I’m using the Aux Send on my board (Yamaha MG102c) to send the mixed signal (minus the caller) to the “mic” jack on this splitter cable. I’m assuming now that this jack is “looking” for a condenser mic and sending +5 volts down the line.

I didn’t think of this until after hooking everything up and finding that everything worked perfectly - no noise our delay or anything. It sounds great.

So…
(A) Is my little Galaxy S2 phone really sending +5 volts down the line back into my Aux Send?

and

(B) If it is, can it hurt it? Or hurt it over time?

Like I said everything sounds great and crystal clear.

The only thing I noticed was when plugging in both stereo headphones and speakers to test the signal. Instead of my Aux Send only sending signal to the Left, like it should, it sends perfectly to the Left and a tiny bit to the Right.

Is this normal? It won’t really affect anything and I know you’ll never use a stereo plug in a mono jack, but is this strange? Did the +5v damage something already? Is this a Yamaha thing? Should I be worried?

Just want to know, since I’m already thinking of upgrading my mixer and I don’t want to damage that one if the Aux Send jack was something I did.

Thanks!!!

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Someone else posted about wanting to do a complex podcast and, of course, wanted to do telephone interviews on top of it. We found a device which properly isolated all the ins and outs but down near the bottom of the device comments was that many cellphones provide “sidetone,” in English: a bit of the transmit sound comes back down the earpiece. It prevents that feeling of talking into a rock.

Almost all telephones do this. Sidetone has been standard since the beginning.

If enough of it comes back, you may start getting feedback problems, or a live, bright sound instead of the straight one you’re interested in.


Most audio systems have blocking capacitors at the input against the event that somebody plugs in something naughty. DC or battery is not sound, so universally getting rid of it is a good idea. I expect the 5 volt battery will not affect anything adversely – even over a long time. Plugging or unplugging something with battery on it will wake you up, though. Turn the speakers or headphones down before you do that.

You can get into trouble with microphone and phantom power systems. There you get duelling power supplies and you may get MicPre 48 volts chugging back down the line expecting only 5. That could be entertaining.

Koz

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Koz! :slight_smile: Thanks again for your help buddy. And sorry bout that long post lol. I’ve been learning a lot about low budget pro sounding podcasting lately. I’ll keep my eye on the forums and try to lend advice anywhere I can. This is a great forum. You guys are doing an awesome job with it.
-adj