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Familiar with Alpine PDX Series?


ice745
11-30-2008, 10:20 PM
I currently have an old Alpine MRV-T420. It was what I could get given the circumstances at the time. I'm currently having all trouble with the amp, and am considering replacing it. At initial low levels, no sound is made, or maybe a little static noise here and there. I have to turn up the volume on my head-unit to almost max before the amplifier kicks on with a burst of static and then music. Then I can turn the volume back down to normal listening levels once the amp "warms up." This started happening a few months ago, and is progressively getting worse.

I have an MRD-M500 for my subs which still performs great. I want to stick with an alpine amp to "match" them. Even though the newer alpine amps look a lot different. At this point I'm not too concerned with what's the "best/top-notch."

From what I know, usually speaker amps are Class A/B, and the Class D amps were mostly for sub-woofers. I was interested in the Alpine PDX-4.100 for the look and energy efficiency. However, browsing the internets I read a lot that Class D speaker amps usually have added distortion and should really only be used for Subs. I was wondering if anyone is familiar with this PDX series, if it sounds good for full-range speaker usage.

PaulD
12-01-2008, 05:42 AM
before you buy anything, try twisting the sensitivity or gain knobs and any other control knobs on the the amp from full low to full high several times back and forth. See if this stops the problem.

ice745
12-01-2008, 04:23 PM
I'll try that. I assume you mean with the amp on and running? I'll post results tomorow probably so I have more testing time.

More info on the problem if it helps any. The channels don't necessarily work simultaneously. It's usually channel 2 on the amp that's out. By reversing input and output wires I ruled out the head-unit and speakers. This was when only the right channel didn't work. But now it's progressed to sometimes neither channel works. And no settings or components have recently changed in my system.

Just to clarify, by reversing the input/output wires, I mean I put the right input into channel 1's (usually left) input. Not that I connected the input wires to the output of the amp. I'm not THAT dumb. With the inputs swapped, the problem stayed on the right side speakers. When I swapped outputs the problem moved to the left side speakers.

PaulD
12-01-2008, 07:27 PM
NEVER unplug RCA cables while the stereo is on !

ice745
12-01-2008, 07:38 PM
No. I didn't unplug anything while the amp was on! I was reversing the channels when the amp was off, then turning it back on to see if the problem "moved." I was just trying to see if the problem was before, after, or in the amp. This was when only one channel was out. I was able to confirm it was the amp's fault. Now both channels are out when I first turn the amp on after it gets cold. I usually turn the volume on the head unit all the way up before I get actual sound, then turn it back down. Sometimes the sound stays in, other times it turns to static and drops out when I reduce the volume back. But once I get the sound to stay on at all volumes, the amp will work fine until it gets cold again.

I went out to a parking lot and played with the gain control. I don't know if it made any difference because I was just using the amp an hour beforehand and it was still working from then. After playing with the gain control I retuned it. I'll be able to tell in the morning when the amp is cold if the problem persists.

ice745
12-02-2008, 05:11 PM
I went out this morning, and the amp worked right off the bat. Playing with the gain knob seems to have done something. However, later in the day, the left channel started to turn on and off with some static. This was at about 1/2 the max volume that it's tuned for. Then it returned to normal on its own after a few minutes.

It seems to me like this is going to be an on and off issue. I'm afraid that it's gonna be bad for the speakers with the amp popping on and off. Any further thoughts?

PlayStation3
12-02-2008, 10:31 PM
the pdx series is nice but they are gain senatitive. i had a pdx4 100

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