need recomendation: head unit with aux in & override

**meep** · 11-01-2009, 05:47 AM

Hi

want to put pc in my car but want to also have a head unit for amplification and FM.

If the PC is running GPS software, I would need the PC on an aux input to 'override' FM or CD playback on the head unit. (so I could hear GPS instructios)

Anyone know of a head unit with (rear) AUX in were the aux in will auto-switch?

Thanks

Peter

**PhilG** · 11-01-2009, 03:08 PM

What you need is a headunit with a Tel Mute line that you can trigger just as if you were muting for a cel phone. Most head units these days have this feature. Then you can run straight to the speakers from the PC. The other option might be to send the PC signal via bluetooth to a bluetooth enabled head unit but I have not tried one of these myself to see if this works.

**soundman98** · 11-01-2009, 04:33 PM

I thought that the tel mute input lead was for muting the audio so you could hear the built in car phone(does anyone have one of those any more?) ring. I could benwrong but I don't beleive that any car radio has a auto switching audio input.

**PhilG** · 11-01-2009, 08:12 PM

Your right Soundman, it will mute the audio so at the same time it's muted, you could feed an amplified signal from the pc straight to the speakers. (You might want to diode the speaker leads coming from the head unit). Not the most efficient way to do it but it could be done. I saw a utility on this site that energizes one lead of a serial connection to turn on amps. That lead could be used to switch relays from the head unit audio to the PC audio. I guess there are several ways it could be done thoretically, but I have no idea without experimenting which one would be practical or provide a reasonable level of SQ.
I have the mute wire of my Alpine W205 connected to my Parrot BT device to lower the source volume when a call comes in on the phone. (Until I get my PC up and running...very soon!)

**soundman98** · 11-02-2009, 11:18 AM

Originally Posted by PhilG

Your right Soundman, it will mute the audio so at the same time it's muted, you could feed an amplified signal from the pc straight to the speakers. (You might want to diode the speaker leads coming from the head unit). Not the most efficient way to do it but it could be done. I saw a utility on this site that energizes one lead of a serial connection to turn on amps. That lead could be used to switch relays from the head unit audio to the PC audio. I guess there are several ways it could be done thoretically, but I have no idea without experimenting which one would be practical or provide a reasonable level of SQ.
I have the mute wire of my Alpine W205 connected to my Parrot BT device to lower the source volume when a call comes in on the phone. (Until I get my PC up and running...very soon!)

ah, i see, i thought you were trying to say that the mute line would allow for a separate input-- you were actually taking about adding another amp to take over the speakers WHILE the hu was muted... that might work, though it could be a very complex setup-- i know that pioneer head units need both the positive and the negative leads going to them for proper amp balancing or something(according to the manual), and any input on the negative leads could cause a issue with the internal amp-- so another alternative would be to use multiple relays to switch the speaker wires to the other amp, though it would not be cheap or easy to hook up the 8 relays for this, and could affect the sound quality.

**millsy** · 11-02-2009, 11:33 AM

I know of a couple of hardware item that will do this
http://www.twowayradiogizmos.com/gemini.html
or this ,might be hard to find,i think it may be discontinued,
http://www.inawise.com.au/910-8001-manual.pdf
there are probably other similar units around.

**soundman98** · 11-02-2009, 11:52 AM

it seems that the gemini unit is a very expensive way to mute your radio to let you hear the gps/radar/etc.

Originally Posted by Gemini

Gemini will mute your car radio to alert you.

it seems that it works by sensing the audio level-- might be a little flakey(i have used a couple of home automation devices that work on this priciple, if you vary the audio level input, the switcher can get confused, or seem stop working all together because the signal can get too low, or switch too much if the level is set to high, even if there is not any audio at certain times.)

note that it says nothing about sending any signal to the speakers hooked up to the head unit.

EDIT: correction-- according to the gemini website, it detects wheather the device is playing audio through the power lines going to the device-- which could be even more troublesome, and the reason it costs so much..

the inawise option looks decent-- it looks to be a mass produced version of PhilG's and my ideas of switching over to a second amp, though again, i don't know how bad it might affect sound quality if you happened to locate one.