car audio question, that may be dumb (You Have Been Warned)

**theheel** · 09-24-2006, 01:38 AM

is it possible to have two sets of input going to speakers in a car?

I wanted to hook up the computer, to an amp and then send the output of the amp to the speakers, but i also wanted to keep the functionality of my stock head unit too. So i was thinking of just splicing the amp wires (to the speakers) so both could be connected at the same time.

I know i would have to mute the computer sound if i wanted to listen to the radio in the car , and vice versa (mute the radio, if i wanted to listen to the carpc), but is this possible?

**scott_fx** · 09-24-2006, 01:47 AM

you could get a couple 4pdt relays and wire them so you can toggle between both inputs. you could also find a a/v switcher

**fuubar** · 09-24-2006, 02:34 AM

You could switch it with a dpdt switch. However the audio signals are both analogue so it is likely that it will not matter if you just splice it. The problem with this idea is if you get a signal peak for both the carputer and the headunit at the same time. The signals are summative so 2-5 V from the headunit and 2-5 V from the carputer = 4-10 V recieved at the amp. If you plan to have the carputer on anyways it may be better to just connect the headunit into the microphone input of the carputer. If i remember correctly, by default windows automaticallty passess the microphone inputs through to the speakers. This solution will interfear with the performance of voice command software.

(if you are listening to my advise you are listening to a drunk. You have been warned!)

**scott_fx** · 09-24-2006, 02:51 AM

haha...drunky!

the one problem with the dpdt switch is that you'd have to run the cable all the way to the switch then all the way to the amps. if you use a relay you can mount it close to the amp and just run a single wire from the relay to the toggle switch.

**Jahntassa** · 09-24-2006, 06:48 AM

Normally i'd be under the impression that having two amplifiers connected to the same circuit would be a very bad thing to do.

Do I have it right? You want to connect the outputs of the stock radio AND the outputs of an external amplifier to the speakers?

Can someone else say if i'm wrong or not? I would think that having one amplifier backfeeding into another amplifier would probably blow something up.

**blkwrx** · 09-24-2006, 09:01 AM

Just use an a/v switch like scott said.

**Jahntassa** · 09-24-2006, 09:44 AM

Okay, just to be sure, this guy is talking about combining the AMPLIFIED SIGNAL WIRES from the OUTPUT of his AMPLIFIER and HEADUNIT.

These are not line-level signals. Putting them through an 'A/V' switch is not an idea i'd reccomend.

**blkwrx** · 09-24-2006, 10:38 AM

I was under the impression he wanted switch between the sound card output and the hu output.

Edit: Ok, I reread it and your right so the a/v switch is a no go.

**Bugbyte** · 09-24-2006, 10:53 AM

Don't do this. As Jahntassa has pointed out, you're dealing with amplified signals and that's a lot more power that just the line levels coming out of a sound card.

If you did want to do it, you'd need a heavy duty relay to switch the amplified signals to the speakers.

I do have a question, though. If you already have an amplified head unit, why do you also have an amplifier? Does the head unit not run into the amplifier? If it doesn't, then what is the amplifier amplifying?