Unwanted "Thump" noise

[mrmsudawgs]

I have a C400 amp powering two Momo C570 speakers and a single MM2104 sub (bridged). Head unit is Alpine CDA-9831. Ever since I installed my system I have had a random "Thump" noise coming from my sub in about the 30 HZ range. It is just a single, short, "thump" that sometimes is repetitive (thump, thump, thump, etc). Like I said, it is random and I may go for a week without hearing it then I may here it all day the next day.

I have checked the ground (its good) and have tightened all power connections - checked everything multiple times.

Today I tried something new. I have disconnected the door speakers from the amp by removing the RCA input jacks going to the amp and also disconnecting the output wires going to those speakers. The only thing left connected to the amp is the sub's wire, the ground wire, the power wire, and the 12 volt turn on lead. The amp is getting no signal from the head unit at all (I also disconnected the rear inputs for the sub). Even with all of those things disconnected I still get the thump noise.

I am now thinking I have an amp problem. Does anyone have any other suggestions? Remember, the amp is now isolated - no signal from the head unit and the only output is to the sub.


Click here (http://home.comcast.net/~mrmsudawgs/Truckaudio.html) to see my system.

Please help!

Mike

[AsSiMiLaTeD]

yeah, my first thought was a grounding issue, but if you've ruled that out...sounds like an amp issue.

I'd email Polk CS for a quick response...

[mrmsudawgs]

I only checked for a secure ground connection. What else should I check for? Why does this sound like a grounding issues to you?

[aaharvel]

i'm not experienced with car-amps or car systems but my home theater Amps have a slight thump when I turn them on/off;
But this is due to the large power supply of the amps. It's perfectly normal. The amps power supply filters and stores energy until the amplifier circuitry needs it during playback. When I turn my home system either on or off, that energy has to go somewhere. The thumping sound comes from the power supply capacitors that release the energy from the amplifier. Perfectly normal as long as it's only doing it when you turn the system on or off. If it's doing it during normal playback- then I don't know what to tell ya. Regardless, I hope this is at least of some help for you.

[mrmsudawgs]

Thanks for the information but system makes the "thump" noise during normal operation.

Does anyone know if there are any known issues with Polk C400.4 amps?

Mike

[mrmsudawgs]

The possibility of "grounding" being an issue has been eliminated. I have just ran a 4 gage ground wire from my amp directly to the negative battery terminal but the "thump" noise has not gone away. Is there any way my sub is causing this or do most of you believe it is now an amp issue?

Mike

[bknauss]

There are no known issues with the C400. Call up customer service. They'll help you out.