Radio and amp connected to speakers at the same time...

**MattW** · 07-16-2001, 04:59 PM

I'm going to be installing my 'carputer' (heh, still can't say that word without a chuckle!) in my dad's Accord for now, until I get my own car, so it brings up a lot of issues. One is, I don't want to replace the head unit (money issues, heh), and I'd like to just use a 4-channel amp instead. But, I'm sure my dad would like to keep using the current radio, so I want to have both connected up to the amp. I'm thinking this could cause problems if both the amp and the radio were outputting power at the same time, or something. So, I should probably use a switch, right? What about relays? I'm worried that electromechanical relays might add some noise to the signal path, but I don't know. I suppose that if this is a problem, I could just use semiconductor relays. What do all of you think?

**Squeezer** · 07-16-2001, 10:08 PM

why not just use an FM modulator for the computer and then use the FM tuner on the head unit. Or if its a tape deck use the stereo to tape adaptor.

**MattW** · 07-17-2001, 02:50 AM

That's what I'll probably do at first, but the sound that way will be quite a bit inferior.

**Aaron Cake** · 07-17-2001, 09:45 AM

Solid state relays will not work for this application. Best bet would be to buy or build a mixer of some type, or just connect electromechanical relays with a switch. Going relays is certainly the cheapest solution, and shouldn't cause noise problems as long as they are sealed from the environment.

Dustin Haug · 07-17-2001, 10:33 AM

If you don't want to use a modulator or adapter, do like Aaron said and use mechanical relays, get one DPDT for each speaker, wire the coils in parallel and you should be good to go. If your amp is very big you should get decent sized relays or you could melt them.

**Aaron Cake** · 07-17-2001, 11:47 AM

I think he's talking about inputting to the amp, not outputting from it. So small relays should do fine.

**MattW** · 07-17-2001, 01:01 PM

Outputting, actually. Well, cool, so I'll go grab some relays some time and hook it up to my home stereo just to make sure there isn't any/too much noise.

**Aaron Cake** · 07-17-2001, 02:10 PM

Originally posted by Matt Waterman:
<STRONG>Outputting, actually. Well, cool, so I'll go grab some relays some time and hook it up to my home stereo just to make sure there isn't any/too much noise.</STRONG>

Huh? By your post above, it sounds like you want to input two different signals into the amp, switching between them (the computer, and the radio). What exactly are you trying to do here?

**cruzc_99** · 07-17-2001, 04:39 PM

I think that he is trying to input two signals in to the amp at the same time too. And if thats the case it shouldn't be a problem. I mean thats the reason amps have auxillarry inputs right. even if you did happen to play the radio at the same time you played the carputer it wouldn't cause any problem, it would just sound like sh**

At least that is what I am assuming because that is how mine will be hooked up in a few weeks.

Let us know how it works

Dustin Haug · 07-17-2001, 05:14 PM

My understanding was that he wanted to be able to switch the inputs to his speakers from the factory radio to his amplifier/mp3 player. He could do this with DPDT relays. Matt if this isn't what you wanted to do post again and clarify.

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