radio noise through sub

[ferenza]

Ever since i fixed my amp, my sub has been making low-toned rumbling and hard thumps when you turn the volume on the radio to 0.You hear engine noises with the car on and when its off the sub still rumble .At first i thought it was my amp again so i plugged in my buddy's amp and i still got the same rumbling noise as before.I read on here about ground loop and i went ahead and did some things to see if they help out:

-replaced power wire from 8 gauge to 4 gauge wire
-replaced rca cables
-replaced remote wire with thicker wire
-added capacitor (3.5 farad)
-turned amp gain down for 75% to 50%
-sanded all interior grounds and checked for corrosion

After all this i still got the rumbling going on but the thumps have become less agressive but is still there.Yesterday i went and added a ground loop isolator
to the rca cables, it completely took away the bass in my sub and made the thump come back 10 times worse.I removed it and said F*** it ill have to live with the noise and as i was sliding the head unit back in i heard the noise again.I started to slide the unit back and forth and the noise was very much prominent . Could this be a bad headunit ground?

Pioneer head unit
Pioneer sub
Alpine amp
Monster cables and wires

*sorry for the long winded read , just want everybody to know what measures i took to eliminate the issue. Thanks*

[SPLCB7]

Yah it sounds like a bad RCA ground just ground out your outer RCA should fix your problem......

[BIGRICH]

you are on the correct path.....simple troubleshooting.

different amp
different wiring
whats the only thing that you havent replaced?

try moving rca from output to output.....i know its not the sub out but im telling you this for testing, not to leave it like that. i think its in the pre out.

[ferenza]

Thanks guys for the help!

I did more researching and found that pioneer headunits are notorious for rca grounding issues.They have a ground fuse on the rca outputs and it blows when somebody fiddles with the rca wires while having the battery connected.Well, ive done that and i guess it blew causing all the wierd noises and such.To fix i put loop connectors around the outputs and took the other end of the wire and wrapped it around the headunit screws and tightened it down.The noise is gone and my bass sounds great.

Hope this helps other pioneer headunit users

[Bad_dude]

Thanks guys for the help!

I did more researching and found that pioneer headunits are notorious for rca grounding issues.They have a ground fuse on the rca outputs and it blows when somebody fiddles with the rca wires while having the battery connected.Well, ive done that and i guess it blew causing all the wierd noises and such.To fix i put loop connectors around the outputs and took the other end of the wire and wrapped it around the headunit screws and tightened it down.The noise is gone and my bass sounds great.

Hope this helps other pioneer headunit users

It's not a grounding issue but rather live RCA swapping cause the pico fuses to blow. It's better to blow the pico fuses than your speakers. The pico fuses blow b/c the head unit is on when plugging and unplugging the RCAs. I ground the RCAs even when the unit is new. Just to prevent this from happening. I also made it a habit to never mess with the RCAs when the unit is on. Always turn it off first.