Thread: How can I tie two inputs to one amp or 2 amps 2 one speaker ??

Originally Posted by integramodder

I would think so long as you are matching low level to low level and high level to high level that you shouldnt have a problem....

agreed

The 98 Avalon with the 7 speaker system has a factory amplifier. To have both the audio from the Factory Head Unit as well as a PC (GPS) you need to build a line level mixer. Something with two stereo inputs and a single pot for crossfade would be ideal. Here is a link to a simple mixer circuit. I'm sure there are others that are simpler and more suitable for this purpose. (Like I said if you could build one with a single pot that would be best.)

http://www.epanorama.net/circuits/linemixer.html

The only small problem you might have is that the factory amplifier has 4 inputs instead of 2. FL FR RL RR. A solution would be to only put the PC (GPS) into the front inputs. FL FR.

Hope this helps.

I believe the solution from walky_talky20 will do it. I just need to build the circuit now. I made the Radio Shack trip and have all the pieces except the pots - they don;t cary them, off to componenets catalog people now. I still have 1 questions though...


This part:
The only small problem you might have is that the factory amplifier has 4 inputs instead of 2. FL FR RL RR. A solution would be to only put the PC (GPS) into the front inputs. FL FR.

I do want to use all 4 speakers though,,,, When I listen to MP#'s or have a DVD movie I'd want it everywhere? Can I build 2 mixers and tie them into the front and rear channels and put diodes in the positive lines so that they don't feed back? I'm almost there.....


also, does anyone have the wiring diagrahm's for these?

I sent you the wiring diagram for the 98 avalon (pdf). As far as mixing the pc into all 7 speakers. You have options. There might be a simpler way using less expensive pots, but I would use two 4gang pots. One for the front and one for the back. The schematic I put up earlier requires 4 pots, but these can be replaced with one 4gang pot which is essentially a crossfade. And you double it to add the rear. Add a second 4gang pot or go to an 8gang pot, but I think the 4gang will be hard enough to find (alternatively you could go to 4 double gang pots, but thats not very user friendly). This is creating 2 mixers. A front and a rear. The reason for 2 mixers is to preserve the fading function: that is the ability to fade the music to the rear. With 2 mixers it is possible to have GPS in the front and RADIO in the rear. If this is not important than you can just split the output of the first mixer and send it to the amps front and rear inputs. I can draw you a schematic if you like and show you exactly where to hook things into your car wiring.

-Also I believe the 10k resistors used in the schematic could safely be changed for 5k's so as to retain more available volume from the system.

-You shouldn't need any diodes at all.

I hope I am not too hard to follow. It is a lot of stuff to think about.

Link to a simple mixing circuit to put inline before your amp
http://www.tkk.fi/Misc/Electronics/c...s/linesum.html
you can conbine two diff line level inputs .
hope it helps