I ordered a new alpine MRP-F450 amp from crutchfield a few days back and installed it yesterday. it is a 4 channel and I hooked it up to my front door and rear deck speakers. after I installed it only the front door speakers, channel 1 and 2, worked and they worked without any problems. the rear deck speakers, channel 3 and 4, would only play very low along with a high pitched, but also low, sound.

the things I did to troubleshoot were:
- alternated the rca inputs (I'm using one set of rca's split into four inputs)
- alternated the speaker connections. the rear deck speakers would work correctly when connected to channel 1 or 2.
- checked all of my connections and made sure the ground was good.

recently channel 2, or the front left speaker, started suffering the same symptoms as the rear deck speakers. the only difference is that it will intermittently play correctly. it was also at this time that I noticed that the low high pitched sound was alternator whine that followed my acceleration in the car.

everything seems to point to a problem with the amp. crutchfield came to the same conclusion and is sending me a new amp. for my own betterment I just wanted to see if anybody knew what was going or experienced anything similar.

sorry for all the words. I just wanted to make sure I gave all of the information without a "oh hey, the thingy is broken" post.

1/21/2007 10:12:05 PM

Sounds mildly ground related. Could be anything though.

1/21/2007 10:17:14 PM

^this guy is the resident car audio expert.

1/21/2007 10:20:21 PM

if it helps at all I am powering two amps, the one mentioned and a single channel 350 watt amp for the subs. I have 4 gauge power wire run from the battery split at a distribution block into two 8 guage wires for the amps. the ground is the same where each amp has a 8 gauge ground combined into a 4 gauge wire with another distribution block.

the sub amp has worked perfectly before and after the addition of the new amp.

1/21/2007 10:38:12 PM

Well, if all the problems are indeed related, then there is something generally just bad about the amp.

If you hadn't told me about the left speaker of the front channel starting to act flaky, I would have told you to see if you don't have the crossover turned on on accident. If you have it high passed at around 50hz, then you'll hear just about everything out of your fronts, and nothing out of your rears (which are going to have trouble playing anything at that frequency and down).

Without playing with it, it's hard to tell.

1/21/2007 11:14:47 PM

ah shit, that is one thing I forgot. I have also tired the filters in all positions (hp, lp, and through) and I get the same result.

1/21/2007 11:18:55 PM

somehow you touched power with the rca ground and fried a resistor. send it back to crutchfield and tell 'em it never worked.

1/22/2007 9:37:52 AM