my new 8 has an aftermarket JVC cd player in it. I see in the trunk there is what I think is an amplifier mounted on the drivers side in a little compartment. I suspect this is stock because it is within a little carpet box that matches the trunk carpet, etc.
anyway, I don't know a lot about stereos, but i was considering chaning mine.

when i popped out the aftermarket to look at it, i see a blue wire marked amplifer going to the radio. I assume this is from the rear amp.
now here is my dumb question, what does the amp do? and i assume when looking for a new stereo i want an "amp wire"? i thought amps had rca plugs, etc.

perhaps this is not the best forum for this topic, but any input or direction towards a more correct forum is appreciated.

Rick

I believe that that is the "Power On" wire. It tells the amp to turn on when the head does.

The stock amp is speaker level input rather than preamp input. Mine came right to life with an aftermarket head driving it with double the stock wattage. All of the muddy went away.

If there is an "on" wire from the head to the amp, should there not be some RCA connections from the amp back to the head? The present aftermarket radio has no rca cables pluged into it.

i fished around with my hand back in the radio hole,but could not find any cables running fro the amp.
perhaps a built in amp in the AF stereo? still, shouldn't the factory amp wire inputs be up there somewhere?

I hate it when trying to figure out a previous hack wire job.
lastly, ther is no plug in harness for the radio. all the wires are just spliced together and run thru some black box, then to the radio. I guess i need to take it somewhere or call crutchfield?
was there a factory plug for the radio

thanks

RCA connections are preamp level. The factory amp does not use them.

The black block should be the adapter and standard connecter plugged together. It has a sliding 90 degree latch type lock. Only about 2" x 2"?

Here's a dumb question, then how does the amp work? If the blue wire goes from the head to the amp to power it on, shouldn't there be something coming from the amp back to the head?
or does the amp go to the speakers?

how does the amp work?

Terry, I appreciate all your help. I know I have a lot of dumb questions, but i want to get this E31 right!

Rick

The speaker level outputs for the head unit go to the Amplifier rather than the speakers.

10 watt per channel for 4 channels, LF RF LR RR from the stock head unit.

The Amplifier takes these four inputs and divides them by frequency for the different types of speakers on those 4 channels Bass, Trebel and Mid-range.
Then it amplifies the signal to a higher value than the input 10 watts. I think about 25 or so.

I am using a 20 watt per channel aftermarket unit in place of the stock head unit. The speaker outputs go to the BMW amplifier. It has its "Sub out" RCAs wired to an Infinity Basslink in the trunk. Works great and sharpens up the signal.