no RCA sub output from alpine HU

[dmc 10+ year member]

I recently put an amp and 12" sub into my car. When I plug my ipod directly into the amp, the subwoofer works great. However, I can't get any sound to my amp from my head unit. The output to the stock speakers works perfectly.

I tried two sets of RCA cables, so I figured that my HU must be busted. I called Alpine and they gave me the same response. However, I bought an identical HU today and the new one doesn't work either!

I don't know what to do at this point, the only components that could be failing are the RCA cables and the HU, and I swapped both of them. I have the cables plugged into the subwoofer jacks, and I verified with Alpine that my HU is set up correctly.

Any ideas?

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[chucku 10+ year member]

Are you shure the sub vol is turned up to 15? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[dmc 10+ year member]

Are you shure the sub vol is turned up to 15? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

yup. I have the following:

subwoofer is on

sub output is max

bass is max

The remote on/off wire from the HU to the amp is working, since the amp power light goes on when the HU is on. Also, i hear a little pop from the sub when the amp turns on.

 

[blackbonnie 5,000+ posts]

what color light turns on with your amp?

 

[Calikid 5,000+ posts]

that's weird

 

[dmc 10+ year member]

what color light turns on with your amp?

There's a red light on top, showing that it's on, and a green light on the side. The protection light is not on.

 

[dmc 10+ year member]

I checked to make sure my HU's ground is good, it is.

When I touch the RCA cables on HU side with my hand, I can hear the sub move a bit. I also tested the cables with a multimeter, they're good.

 

[99StangGt 10+ year member]

Have you hooked the rca cables to another output? Hook them to the rear or front outputs and if the sub works then you know the rca cables are ok.

 

[blackbonnie 5,000+ posts]

yeah on my HU, my sound bass just quit one day, so i ended up testing everything i possibly could think of. opened up the amps, nothings wrong, check the wiring, perfect. i couldnt figure out what it was. so i hooked it up to my rear outs, instead of my sub out, and waallaa. it worked. maybe try that^^^

 

[dmc 10+ year member]

solved!

Here's what I did:

I got an adapter to plug headphones into the RCA outs of the head unit. All three sets of output (front, rear, sub) worked!!!! I plugged the sub back in, no luck.

Then, I plugged headphones into the sub RCA jacks on the amp side of the cable. That worked too!! At this point, I suspected some bizarro grounding problem. I set up the following:

RCA cable from HU -> RCA to headphone adapter -> headphone female to female adapter -> headphone to RCA adapter -> amp input

Voila, my amp worked!

Now get this: I unplugged the set of adapters, and went right from the RCA to the amp (the setup that never worked in the past). It worked this time!

Right now, my amp is grounded to the trunk latch. I'll be moving the ground to a better place soon, and I'll let you know how it works out. Thanks for all the help! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[blackbonnie 5,000+ posts]

so after you did all the adapters, you unhooked all of them and hooked your RCA's back up and it worked fine?

 

[dmc 10+ year member]

so after you did all the adapters, you unhooked all of them and hooked your RCA's back up and it worked fine?

Yup.

Maybe there was a charge in the HU or amp that had to be grounded out?//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[blackbonnie 5,000+ posts]

weird

 

[Calikid 5,000+ posts]

that's odd.