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One channel suddenly louder than rest. Blown Amp?

02-18-2009, 12:12 PM
I've got an Infinity 475a 4 channel amplifier connected to infinity speakers. Working great for 8 months now, but today I had it cranked up to no more than what I usually listen to it at and suddenly the rear left channel becomes much louder than the rest. I of course went through all the settings on the head unit, and checked all my connections. Nothing is out of the ordinary as far as that's concerned. I swapped the right rear and left channels to see if it was coming from the amp, and sure enough it does the same thing when the right speaker is swapped with the left. The audio coming from the left channel on the amp is at least twice as loud as the other channels, and is very bass heavy. I'm almost positive that something is wrong with the amp, but I was hoping maybe someone here could give me a few suggestions, or possibly tell me if this is a symptom of a blown amp or what. Any tips, help, or suggestions would be much appreciated. Thanks.

This experience has definitely turned me off from Infinity products. I've had one defective amp directly out of the box and one blown speaker within a month of putting the system in. My JL audio and Polk equipment keep on going....

02-18-2009, 09:25 PM
The amp seems fine after you let it sit for awhile. You start listening to music and after about 45 minutes or so, it starts doing it again. All other channels are normal volume and the rear left starts playing about twice as loud and distorted. It's not overly hot, and no protection kicks in. I've never heard of an amp behaving this way before, but that's just me.

06-22-2009, 01:31 PM
Just an FYI for anyone who has this amp. I've finally discovered that it's actually the gain control for the rear channels that is causing the issue. If you press on the gain control knob everything goes back to normal. What I eventually ended up doing was actually inserting a small piece of metal into the opening around the knob to slightly put downward pressure on the knob itself. This has completely solved the issue with the one loud channel. I know for a fact this is caused by the amp design allowing this particular amp to get so hot. From every review I've read this is just the way this amp functions; but apparently due to the heat it's warped something inside causing this issue. The amp still works great, I just had to rig something up to get it to function 100%. According to an IR thermometer that I have the amp will get up to 150 - 180 degrees if you have it cranked high enough for around 45 minutes. Around the 45 minute mark it'll audibly reduce the power output to keep from completely overheating. It hasn't shut off on me as of yet, it just seems to reduce it's power output by around 10% or so. I'll probably end up mounting a fan to the top of the unit right around the area that seems to get the hottest.

06-22-2009, 07:09 PM
kinda sad, Infinity used to be a good name

06-24-2009, 04:59 PM
Sounds like a bad gain control or a cold solder joint on the board where the control is soldered. And why a piece of metal? If that piece should somehow find it's way into the amp it could turn into smelly doorstop from it bridging some circuits and shorting the whole mess out.

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