Multiple audio devices..How?

[KF7GTC]

Hi all,

I'm hoping that someone has an easy answer...

I would like to connect several devices into my vehicle audio system...at the same time.

I have an HT and a scanner I'd like to hook into the speakers of my vehicle. At first I tried connecting the headphone jacks to a y-connector to the AUX line-in on my stereo. Nothing. I can connect one at a time and it seems to work, but only if I have the stereo in AUX mode.

Here's what I'm trying to accomplish: I would like to hook all these devices together then be able to monitor all of them at the same time. Superimposed over the car's stereo system. So I can have the FM radio on, then my HT on which ever freq I need, then the scanner input for the local police/fire stuff. I would like to be able to vary the volume of each one on the device through the system. That way I can set each one individually as needed.


That's a long explanation for something that should be pretty simple...


Any ideas?

THX,

KF7GTC

[KF7GTC]

Wow....NO ONE? Come on...someone has to have an idea...?

[W8JI]

If your stereo has a line level input you can bridge all the devices together though an isolation transformer (one for each device) into a series resistor that sums all the audio outputs at one point.

It would take a few 4-8 ohm transformers with 200-1200 hi-Z windings, two or three resistors per channel, and that's it.

I do that here inside my house into an audio amp.

73 Tom

[KE3WD]

Even if using Isolation Transformers (recommended to keep the smoke inside the devices, BTW) you couldn't listen to the FM radio at the same time through the AUX input.

That would take some rather serious butchering inside the car radio first - and isn't recommended.

Do not try to hook the audio output of two pieces or more gear together in a simply Y again, you got lucky the first time, worst case scenario is blown audio output stages in today's transformerless output solid state gear.

Audio isolation transformers may be used, but also may be pricey. on the other hand, one might press standard transistor style audio output transformers into use, backwards, such that the radio output is wired to the 8 ohm side and the 2,000 ohm or so side is used as the output to the AUX input. Then you could safely mix the outputs of more than one into that AUX input. I'd use series resistor with the output of each transformer as well, to make a resistive mixer out of the thing - google for the basic resistive audio mixing circuit, then put the transformers in front of each input.


73

[W0VYE]

Wouldn't you want some way to at least mute the FM tuner when the other devices are active?

I have to say this sounds like seriously distracted driving to me. But I'm old. 73

[KK4CLD]

I use this

It takes inputs from the scanners and FM radio I have and gives me a clean mix into the car stereo aux input.

Generally I keep the FM radio at 70% volume relative to the scanners. The scanners at 100% come thru loud and clear over the music.

Works for me.