Pre-amp signal to factory amp

[cobra mk8]

So I installed a new head unit in my 93 with the amp. It was recommended to use the wiring harness using the preamped outputs of the HU into the factory amp. Turn it on, nothing. Only loud popping sound and a hint of music when turned up really high. Does the same thing when I swapped to a different head unit.

Now when I don’t use a pre amp signal and go with a wiring configuration such that a amped signal from the aftermarket head unit into the factory amp (double amped)..works and sound great.

I do know:

Power is getting to amp.

Amp gets warm.

Preamp harness checks out fine.

Was wired correctly

This surprises me. Is this normal?

 

[LaserSVT]

The factory deck does not have a pre amp level to send to the amp. The factory deck has an internal amp and thats the signal used to feed the JBL amp. Whoever told you to use the pre amp level outputs knows nothing about Ford stereos.

 

[cobra mk8]

Man thanks for the reply, It was a cruchfeild tech…three of them. They all said they will not sell anything other than that recommended preamp harness… as a amped signal to the factory amp could damage it. What a bunch of wasted time.

 

[LaserSVT]

Crutchfield has great research for the most part but the people you speak to on the phone only repeat what their books tell them to say. Sometimes stuff slips through the cracks.

All Ford decks with the exception of the Alpine systems just have speaker level outputs. The decks only have 8-9 watts RMS and thats about what a high voltage output deck can do so if you have a deck that has 5v+ output you can kinda make it work. With standard decks that have a 2v output its just not enough to drive the amp.

Now aftermarket decks can usually pump 18-22 watts RMS so you can overpower the amp but the speakers will distort before the amp starts to clip. Just dont crank it all the way up and you should be fine.

Really though it would sound way better and louder if you ran new wires from the new deck to all the stock speakers. That 22 watts RMS is more then what the JBL amp can push and most decks have a lower THD then the JBL amp anyway.

 

[cobra mk8]

Ya the deck I got has 5V+. I thought about bypassing the amp but I understand it also has a crossover in it. I kind of think It would be a mess to rewire and be able to distribute the highs and lows to the right speakers but I don't know. I’m really surprised how well everything sounds even with the oem speakers.