I currently have an alpine mrd-m605 powering 2 10" subs. All the sudden the bass is barely noticeable. I checked all the wiring and it is correctly hooked up - I have a total of 3 amps. The other 2 feed the rest of the system. Confused, I checked the gains and it was set exactly where I had it...1.5v (0-4v). I adjusted the gain to 0.4v and the speakers came alive but Waaaay too much distortion. I checked the x-over and it is set to 80hz. Adjusting the x-over had no effect.

All amps are on the same ground/power and subdivided into distribution blocks. I have 1awg then splits from there. The ground and power are solid - no issues.

I have never had a slow failure in a amplifier. So my question is...does this sound like the amplifier is slowly failing? Figured somebody might have experienced this before.

 

Might be a failure in the RCA cables or HU. Anytime I've had an amp fail, it was catastrophic death.

Try switching the RCA feeds around, see what happens if you put the feed from the rear speakers into the sub amp, and the sub feed into the rear speaker amp. Then swap cables at the HU. Those tests should allow you to isolate it being the amp, cables, or HU.

 

Weird. I have an Alpine MRP-650 that all of a sudden just stopped turning on the output. It must be something in the input op-amp or transistor circuit I think that has broken down and is not flowing current (turning on) until voltage is high enough. I can get it to turn on by turning the head unit volume way up (thus kicking the signal to the amp input up), or by adjusting the gain. At that point, it will stay on at any volume until I turn the radio or car off again. So, I just crank the volume until the subs kick on and then lower it back down....it's at the same volume level number every time and since my hu has a **** it's not a big deal.

I haven't dug into it any to find out if it was a problem with the output of the head unit or the input of the amp since I can get it to work, but your problem has me convinced it's in the amp.

 

I once owned an Alpine amp, mine played fine for sometime then randomly one day it started acting weird (can't remember exactly this was like 8+ years ago) and what it was, as strange as it may sound was, it was to close to the sub (I guess the magnetic field of the sub was screwing with the digital controls or something) so I moved the amp away from the box and it started playing normal again.

 

The amp is fried...just confirmed. So weird, it was a slow, slow death then nothing. Having 3 amps, I swapped some cables over and the subs powered up fine.

I think the biggest indicator was almost no sound at 1.5v gain. Adjusting the gain to 0.4 made the subs push some air but was too much distortion. I started to get "CUR" message on the amplifier screen - which means drawing too much current. Next day, nothing! Amp s*it the bed.

I purchased an Alpine MRV-500m as a replacement which is a significant upgrade and being much smaller, fits my amp rack perfectly.