I am currently in the process of updating my sound system, and I had a couple questions. This is my first time doing car audio.
The previous owner installed an Alpine MRP-F250 amp, upgraded the door speakers with components and added tweeters. He left the original head unit. I am adding a new head unit and a pair of Polk speakers in the roll bars.
I got everything installed fine, but I had a few questions.
First, the stock head unit obviously didn't have RCA outputs, so a little black box was used to convert the speaker wires to RCA, don't remember what exactly it was, I think it upped the power output (said something about 15 to 1...). When I installed my new head unit, I decided to wire it straight to the amp, but when everything was hooked up, I could barely hear the speakers, even on max volume. I re-installed the black box, and sound levels were fine. I made sure that I had hooked everything up correctly, including the remote turn on line. Still no luck, so I spliced the remote line back into the black box, hooked it back in, and everything was fine. Can't figure that one out.
Second, my new head unit has a volume range from 1-50, but right now while playing a CD I can only get the volume to about 35 before I get distortion. I followed the Amp owner's manual instructions for tuning it, which gave me good sound, but didn't change the max volume I could set. Just wondering if there is anything I can do...
from the owner's manual:
"Input Gain Adjustment Control
Set the MRP-F450/MRP-F250 input gain knobs to
the minimum (4V) position. Using a loud cassette
or preferably a CD as a source, turn up the head unit
volume until it distorts. Then, reduce the volume 1
step. You can then increase amplifier gain until the
sound from the speakers becomes distorted."

I'd really appreciate any help,
Thanks

 

What new head unit do you have, and does it have pre-outs for connectnig to an amplifier?

Did you connect the speaker outputs from the new HU to the amp, or did you connect using the pre-outs (assuming the new HU has these?)

The correct way to use an amp is to connect the pre-outs from th HU to the amp, and thence to the speakers.

If you've connected the speaker outputs to the black box to get a line level output to thamp, it should all work ok. Your gain levels are set too high if you're getting distortion half way up the volume range. alternatively, the distortion is a function of the "black box".

 

From looking at the amp's layout, it seems to have 'speaker level input' and 'RCA input'. You should now be running RCA to RCA...is this correct?

reference link:
http://www.crutchfield.com/S-fBrXQF4336W/p...e-MRP-F450.html

 

Yeah, I tried running RCA to RCA and I got no volume, at 100% head unit volume (50) I could still barely hear the speakers. As for the gains, I set them according to the amp manual, and I was getting distortion at 35 at the lowest gain setting... so I'm thinking it might have something to do with the black box...