I have a JVC MP3/CD player in my 4Runner. Today I noticed that when I shut of the ignition my speakers make a *thump* sound. It just started happening today. Anybody know what this might be???

 

Is this in the Metro?

 

Nah...I had to crash that Metro. I'll have the insurance company cut you a check.

 

Saaaweeeet!!!!! Can I get another Metro?

For old times sake - R.I.P.

 

That was just wrong.

 

Had to dust that one off...

 

I found this on the subject: The large capacitors in an amp store up the electricity, and it discharges them at shutdown. This energy is residual energy that is much weaker than the bass signals that play during the music, so there is no risk of damaging the speakers.

I found an even better explanation:
Is there a remote on wire on the amp? look at the documentation for the amp and see if it is an autosensing amp. Those delay the turn on until after the head unit is initialized. Thus turning the amp on AFTER the head unit has stablized. The delay is not very long, but enough. If it is not autosensing, then it may require a remote on wire that basically performs the same function. On initialization of the head unit, the amp is signaled thru this wire and amp turn on is delayed bypassing the turn on thump. There may be an issue with installing the amp physically closer to the engine compartment than before. You might try moving it back to the trunk, wired like it was before to test that. I know it os a PITA to do that, but that will tell you if that is indeed part of the issue. I have had some amps that are extremely sensitive to the type of Radio Frequency interference that an alternator emits. It could be that the difference in physical space between the amp and the alternator is enough with the amp installad in the trunk area to eliminate picking up the RFI from the alternator.

It could also be that the RFI is fooling the autosensing circuit in the amp (if it is autosensing) into sensing the RFI as audio signal, thus negating the power on delay causing the thump as well as the alternator whine you,re hearing.

You might try this before you attempt to install filters. If the RFI is being sensed by the amps position to the alternator rather than having it introduced into the amp thru the wiring the filter may not help. That is not to say that they cannot help, bit it is best to Identify how the noise is being introduced into the amplifier.

Hope this helps!

 

Thanks, buddy.

 

Off-pop eliminator

 

That's the nice thing about having amplifiers with soft starts and shutdowns. They prevent that thump.