Subs playing without RCA cables being hooked up?

[Slammed 5,000+ posts]

Subwoofer RCA cable is not connected to the amplifier yet the subwoofers seem to be playing (sounds like alternator whine/static). Subwoofers sound the same when the RCA is plugged into the amplifier. I checked all the RCAs and they are fine. Front and Rear speakers play fine (with little alternator whine).

This started happening once I installed my head unit. But the Kenwood was brand new and everything was hooked up properly. The amp was fine prior. Subs also played fine when using my Audiocontrol LC6.

Again, static/alternator whine plays through the subs when any of the rca cables are plugged in. Subwoofers play a bit loud (with whine) only when the 2 or 4 channel input is selected on the amp...not the 5 channel option.

My amp:

MTX Car Audio - Archive - Thunder405

My h/u:

Kenwood KDC-X395 (KDCX395) CD Receiver w/ LCD Display & SAT Ready

Please help //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

Click to read more...

 

[subzero 5,000+ posts]

I had that before. like engine whine bad ground somewhere. Someone told me that some amps with bad internals might have got over heated and ruined board circiutry too. Start with the obvious first and then if nothing else, take the amp in to be checked.

 

[Slammed 5,000+ posts]

I hope it is not the amp //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

It is weird that prior to installing my headunit the amp and subs were working fine.

Thanks

 

[REDz28 10+ year member]

Check your grounds maybe knocked something loose when installing new Hu? Your amp is grounded of course right? Bare metal contact?

 

[Side Show 10+ year member]

ground loop issue?

 

[Slammed 5,000+ posts]

Ok...I messed around with my wires. There is only a little bit of alternator whine (I grounded the amp differently)

But...I still have problems:

Sub is still playing slightly with no sub RCA plugged in.

Sub plays a bit with rear RCA plugged in and/or with front RCA plugged in.

Sub plays louder when 2 channel or 4 channel inputs are selected on the amp (no sub RCA plugged in).

When sub RCA is plugged in (and when 5 channel input is selected) the gains have to be almost all the way up for the sub to play loud.

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[audiosniper]

get rif of the kenwood i c it all the time at my shop dont know why they do it but also make sure you power wires arent crossing your rcas

 

[TheUnderFighter 10+ year member]

Sounds like an amp issue if it's making noise without the RCA's connected. If you're having problems before the RCA's are connected, the only thing it could possibly give it a signal, is the amp.

 

[Kangaroux 5,000+ posts]

Ok...I messed around with my wires. There is only a little bit of alternator whine (I grounded the amp differently)
But...I still have problems:

Sub is still playing slightly with no sub RCA plugged in.

Sub plays a bit with rear RCA plugged in and/or with front RCA plugged in.

Sub plays louder when 2 channel or 4 channel inputs are selected on the amp (no sub RCA plugged in).

When sub RCA is plugged in (and when 5 channel input is selected) the gains have to be almost all the way up for the sub to play loud.

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By play loud do you mean to make the sub move a lot or to get a lot of output? If the sub is moving a lot but not much sound is being produced try flipping the rca's. Also check and make sure your sub's voice coils are wired up right and they aren't out of phase. Where did you reground to? I am almost positive your ground is the issue you're having.

 

[Slammed 5,000+ posts]

Thanks for the quick replies

Power wire is not crossing the rcas or speaker wires

I tried flipping the RCAs but had the same results

The subs get louder but not as loud as they should be. I double checked the wiring of my subs.

Again, everything worked fine when I had my Audiocontrol LC6 installed. Everything went to ***** once I removed the LC6 and installed my h/u.

I sanded down the metal on my trunk's floor and tightened the bolt. Minimal alternator noise is present (it was much louder before)

 

[rfmayhem 10+ year member]

its the amp my mtx amp did the same crap try grounding the rca out at the amp sometimes that help if the amp aint to messed up