Help needed: line level interrupt

[ChuckRuiz]

Hey all,

I'm hoping someone can help me either a) identify the part that I am looking for or b) help me build one.

Context: I've been into car audio for about 20 years. My current setup is pretty high end and sourced from the balanced outputs of my factory head unit. Everything looks nice and stock in the cabin. I'll be adding an Escort 9500ci radar/laser system within the next few weeks (it's in the box, waiting on a rainy weekend for installation).

Goal: I'd like to avoid using the little amplified speaker that comes with the Escort and have it interface with my audio system. The effect that I'm looking for is to emulate what happens when your in-car nav tells you that your next turn is coming up... The interrupting audio source gets priority, ideally cutting the initial source to a reasonable percentage of original volume and have the interrupting source at its set volume.

Does something already exist that I can buy off the shelf? 2 pair of inputs, one pair of outputs and maybe some sort of % mute selection?

Or are there any aspiring EEs here that want to take on this project and take it to market?

Thanks,
Chuck

[Perry Babin]

Check the Scosche and PAC sites if no one has any specific suggestions.
Scosche Industries
Pac-audio.com Products | iPod Integration for your car and More by Pac-Audio - Connecting you to the future

[RiLoWa]

The brand Audiosource makes home amps that have circuits in them that may do what your looking for. Look at the manual to confirm.

http://www.audiosource.net/pdf/amp100_manual_web.pdf

Maybe someone (in the solid state forum) with one of their amps can crack one open and send you info on how it works to get you started.

[ChuckRuiz]

Thanks, guys. Any other suggestions out there?

[el gordo]

Hello ChuckRuiz, maybe you must to build and design your own application. Between the so many electronic volume control ics you could use TDA7313, it's used by many car stereo manufacters. TDA7313 have 3 dual inputs selection, bass & treble all I2C controlled. You can use also PT2313. You must to use a microcontroller to command functions and improve volume attenuation, with a mixer or selecting voice channel when nav is talking. Another idea is, without using volume attenuation, a 4066 analog switch to mute line and enable voice; or select an attenuation from a resistor network and a op-amp for mixing signals; an so...
Nothing more specific in my mind now.

Good night.

[RiLoWa]

Here is a schematic I found for the input section of an Audiosource AMP200 / AMP300 that does what I think you want. I just received an AMP210 that I can take and post pictures of if you want.

The key is you would have to create the ±15v to supply the 4558's and adjust VR300 to get an instant interrupt.

Also as a note, this does not attenuate the radio input, it switches to the higher priority input via relay.

[AKHeathen]

just what vehicle is it? there may already be some databus interface modules that will allow you to feed a singnal to your factory system as well. other than that, i would second the notion to build a source switching in-line controller, which will interrupt your ballanced signal to the amps. i know there have been rca to ballance and ballance to rca modules built in the past, i think i saw a matched set for sale yesterday, but perhaps they still sell them, and you would have something to start with and modify your interrupt signal

[sofaspud]

There might be a cellphone gizmo that could be adapted to your Escort. I couldn't say what or how offhand, but the same thing is done there and it hasn't been mentioned.

[ChuckRuiz]

RiLoWa: This looks interesting. I think there are some possibilities here; I'd have to talk to an engineer to help me determine if we could delete the delay circuit. Human response to sound is already two seconds, if I add an additional three I'd likely be sitting with red & blues in my rear view.

AKHeathen: It's a 2008 BMW M3. I've tried to contact a few electronics shops who seem to specialize in MOST Bus interfaces, but I haven't received any replies. This would be the most ideal solution, and the one I thought of originally, however haven't found anything. If anyone does know of a MOST Bus interface for this situation, please let me know!

Sofaspud: The cell phone gizmos also add a 2 second delay, so the human reaction time goes to 4 seconds once the detector is triggered. This is something that my old car stereo buddies brought up, too. But if I'm going through this much trouble, I want some switching in the ms range, so that the alert is as near to realtime as possible.


This is great, guys! I really appreciate the input!!!

-Chuck-

[Perry Babin]

If PAC or Scosche didn't have anything, you can use relays to switch the signal lines. You'll have to determine what sort of signal you have when the detector sounds. You need to measure the DC voltage across the 'speaker' terminals of the detector when it sounds. Measure directly across the terminals and measure with the black probe on ground and the red probe alternately on the two terminals. What are the DC voltages for those three tests when it's sounding.