noise from sub without RCA hooked in

[Imshirazy 10+ year member]

Hey guys, today when I turned the key to my car (car not fully on) even though my head unit had the volume fully turned down, i heard a slight rumble. I wasn't sure where it was coming from so i checked all my speakers, it was the sub.

The sub was playing a non stop solid note, no idea what hertz the note was though, im sure that might be an important piece of data though...

Only the sub was making the sound and no speakers, so i unplugged the RCA to see if it was head unit related, but nothing changed at all, not even a slight stop in sound when i unplugged the sub RCA.

My sub is an alpine swx-1042d and hooked to an autotek sx-777 (7 channel amp)

what could be causing this? It doesnt do it when the car is off so it's at least not like the amp stays on

and i think it might do it do even when the car is on but the car volume is louder than the rumble and i didnt check, but the music still plays crystal clear even through the sub, what could this be?

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[vehementSPL 10+ year member]

Could be multiple things. I don't know a LOT about amps. Sounds like it could be a ground or something going bad in the amp but AGAIN I am no amp expert. Also can be many other things. but those are the first things I would look at

 

[mile098 10+ year member]

u got a bad connection somewhere...check the amp and the sub...all of them and re-do em and see if theres any difference

 

[audioholic 5,000+ posts]

Im sorry, I didnt read your post, but I dont think I need to. If the sub is outputting sound even with no signal going to the amp (RCA's disconnected), you have one of 3 problems... 1) poor connection/ground for the amplifier, 2) the amplifier is mounted directly to metal (shouldn't be), or 3) a speaker wire has come loose. Its probably number 1 or 2.

 

[Imshirazy 10+ year member]

most likely number one then, but it didnt happen today, odd...

 

[Echo42987 10+ year member]

Bad ground or cable majority of the time.

-Nick-