Audio sensing circuit.

I  need help. I cant find this anywhere on the internet. And hopefully someone in this forum can shed some light.

I am not sure if I need some sort of trigger, low to high type convertor or gain control or relay or amplifier.

Heres my dilema. I need some sort of audio sensing circuit. When there is any audio on an RCA pre-amp level line, I need it to trigger +12V. So when an audio source is turned on, this circuit senses it via the rca, then triggers possibly a relay for +12VDC. 

How can I go about making this work. I tried a PAC trigger that said it would trigger off of 0.7V, but the voltage is to low on the RCA.

why cant you just use the remote turn on lead going to your amp? otherwise i would suggest just using a ingition 12vlts or something on that line.

I can't do that. I have a radio that has an AUX input port. But the only way to get into AUX mode is to put constant 12VDC on a certain wire. When the 12V is removed, the radio comes out of AUX mode. So I wanted the radio to go in and out of AUX mode whenever the AUX device is power on/off.

The AUX device could be anything Satellite radio, DVD player, MP3 player, Basically anything with a pre-amp level audio output. So I figured the only way to make this work is to somehow trigger +12V, when their is a signal on the input RCA.

Any more ideas would be greatly appreciated.

I am not sure I follow what you're saying. The way I have it hooked up now, is I have a switch that switchs +12V to the "AUX" line on the radio. This sets the radio into "AUX" mode.

I want it to be automatic, with no manual intervention required....i.e. no need to flip the switch.

So I dont know where the switch comes in play that you're talking about. The voltage sensor sounds good, but wouldn't it always sense the voltage is present feeding the aux unit, whether it is powered on or off, the voltage would still be feeding it.

what turns you aux source on and off?

You good with electronics? if so, take the cover off of the radio tuner and get a DMM. Start where the power goes in and follow it, there should be a relay in line with incoming power that turns the unit on. All you would have to do is sodder a wire to that and then wire to relay to power the aux input. Is it pionner or kenwood? If its pioneer, i'll go take mine apart and tell you exactly where to put the wire.

I knew that was an option, but the thing is, I sell a custom made AUX input cable. So right now I am selling them with a switch to turn the radio into AUX mode. I just wanted to offer my customers an easier way to switch the radio into AUX. automatically when their aux unit is turned on.

Right now I am tinkering with an audio-amp chip and a relay. But so far no luck. The amp puts out 9V whether or not the rca input is hooked up or not. The RCA input is between .2mV and 8mV.

Thanks for all your ideas so far.

The Right Connection, yeah bassicly just get a set of y's and run a set to the converter and a set to the deck. Let me look here for a part number that might work.... N-807, its used to break a cirucuit when the music is turned off you could rewire it to work the opposite. LVT, low volage triger. BLD  its a line driver, dont know if has a output on it or not.  N-455 line out coverter, nothing special.

1-800-429-6200 

Yes, I have a PAC low voltage trigger, but the voltage on the RCA is to low. So I put the rca to the line driver to try to increase the voltage. The low voltage trigger still did not pick it up. And the line out convertor is used to convert high speaker level to low rca pre-amp level. Are you saying that this LOC can be used backwards and convert LOW to HIGH?

How can I get all that to work together?     Is there any other way that would be more cost effective, and smaller in size? Is there any way to just build something myself? Last night I was almost onto something. I increased the rca level by using an op-amp, which increased it to 2V. I then sent it to a relay. But the relay then latched which is good, but then the voltage jumped to about 5V, and wouldn't unlatch, when the music was turned off.

Again, thx for all the help