I have a head unit with line outs connected to an amp under the passenger seat. I also have a Navman PiN with a 2.5mm stereo head phone level output.

Ideally what I would like is to be playing music, but have the Nav instructions come in over the top. I assume I need to mix the signals before they enter the amp. What sort of circuitry do I need for this and how do I minimise noise?

 

Ideally, you'd want the stereo volume to drop or cut out when receiving voice guidance. Most nav units have an interrupt signal that they can send to a headunit to cut the volume to the music so the nav messages can be played.

However, with a handheld unit, that's probably not possible.

Guess my post has no real purpose.

 

Except to make me think!

My circuitry should detect the increased level from the nav and ground the Att lead hence dropping the head unit source. Brilliant!

 

90% of headunits have a mute lead wire....

Just tap into the wire from the nav, and splice it into the mute wire. (THis works on alpines, im not sure about others)....when the NAV sends a signal, the radio will cut out.

However, some headunits the mutelead with do just that...mute everything. Alpines mute lead is made for cell phones...so it just mutes its own sources, and not externals.

 

Damn, I clicked before the graphic had loaded and accidentally put you on my ignore list. Sorry, just removing you form it.

My head unit has a Mute or Att lead. But it won't affect the amp. So I just splice into the line ins and use a relay to drop the mute to earth when the line out of the Nav goes high. I would like instant response, but it would be good if there was a short delay before the sound comes back in case of pauses in the instructions.

I'd love to hear from Modify or similar about this.

 

I can think of a fairly simple circuit. Run the nav audio through a rectifier, then through an op-amp with really high amplification to create a square wave (the heavily clipped signal will be high whenever the audio is there). Add in a delay timer (such as a 555, or similar) to give the pause at the end during short nav silences. That simple signal is used to mute the stereo signal.

But don't ask me to put it together... I'm swamped as it is.