Amp dilema, any suggestions???

kenjancef · 05-21-2009, 09:30 PM

Ok, so I decided to install a 4-channel amp that I had in my Jeep about 5 years ago. It is a 400W amp, and kinda cheap, but it worked, and pretty well. So I get it all hooked up, and WHAM! I get alternator whine. After regrounding the amp and making sure the power and RCA's were apart, I still get the whine. So I then check the RCA's... I switch the fron to rear and rear to front, still there... I then unplug one set of RCA's to see if it was the RCA, and WHAM! the noise was gone. But just to make sure, I use the other set of RCA's alone, and the noise was gone...

So.. the short of it is that if I only have one set of RCA's connected, whether the front or back, but just ONE set, all is fine. once I connect the second set of RCA's, whether front or back, the whine comes back.

I know enough about amps and such to be basic to pretty intermediate, but this has me stumped! I think I have a ground loop isolator laying around that I can try, but I'm not sure if that will help.

And I know the amp is old, so it might be the amp. I am not opposed to dropping $100 or so on a new amp (yea, I know that's low, but I'm not out for a comp setup).

So if anyone can shed some light on this for me, I would GREATLY appreciate it!!!

Thanks!!!

Ken

PaulF · 05-21-2009, 09:54 PM

This sounds like it could definitely be a ground loop problem.
Check out this page: http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Are you using tow cables which are EXACTLY the same?

colin · 05-21-2009, 10:07 PM

Try grounding the two RCA grounds together, keep everything running at the same levels. It appears that inside your amp, the grounds are not the same or in your computer the grounds are not the same or your cables have largely differing resistances...

kenjancef · 05-21-2009, 10:42 PM

Quote: Originally Posted by PaulF

This sounds like it could definitely be a ground loop problem.
Check out this page: http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Are you using tow cables which are EXACTLY the same?

No. One RCA is from an amp kit, the other I bought separate, but they are both from the same company (Rockford Fosgate), bought the kit and cable from Best Buy.

Thanks for the reply.

kenjancef · 05-21-2009, 11:10 PM

Quote: Originally Posted by colin

Try grounding the two RCA grounds together, keep everything running at the same levels. It appears that inside your amp, the grounds are not the same or in your computer the grounds are not the same or your cables have largely differing resistances...

How do I ground the 2 RCA's together?

Thanks!

PaulF · 05-22-2009, 06:26 AM

I would say, try the system with two of the exact same RCA cable. The different lengths may be messing up the grounds. For testing purposes, use one of the rca cables you already have and connect ones of the wires to the red connector on one input, and one on the red connector of the other input. After, do the same for the white. If there is no noise in either of these setups, then it's the the cables.

WuNgUn · 05-22-2009, 07:59 AM

Maybe one of the RCA chassis plugs on the amp isn't properly gounded...maybe it broke free with a WHAM!?
But it sounds as if it's choosing the RCA's as a partial power ground when they are both connected...which means WHAM! Your power ground isn't good enough...Have you thought about doing the Big 3? It's something any car audio guy should do, and you never know, it could just as easily disappear, like WHAM!
Maybe make your own RCA's as well...with a ground/drain connection only at the amp end?

kenjancef · 05-22-2009, 04:34 PM

Quote: Originally Posted by WuNgUn

Maybe one of the RCA chassis plugs on the amp isn't properly gounded...maybe it broke free with a WHAM!?
But it sounds as if it's choosing the RCA's as a partial power ground when they are both connected...which means WHAM! Your power ground isn't good enough...Have you thought about doing the Big 3? It's something any car audio guy should do, and you never know, it could just as easily disappear, like WHAM!
Maybe make your own RCA's as well...with a ground/drain connection only at the amp end?

WHAM!

Thanks for the reply..

It is a cheap amp anyway, so if the problem IS with the amp, then I will just go out and buy a real amp... I got it off eBay about 5-6 years ago or so.

But what I did was put a Ground Loop Isolator on one of the RCA's and it seems to have fixed it.

So for a semi-amature car audio guy, what is the Big 3? Sorry if I should know that, but I don't.

Again, thanks for the reply!

Ken

jake789 · 05-23-2009, 04:36 AM

WHAM! This is one way to ground the rca's (usually needed in Pioneer HUs)

Big 3:
http://tinyurl.com/o4zcuw

cloudstrife · 05-24-2009, 12:47 PM

Hey guys, I need some help. I have three amps in my 2001 Cougar. Two power two sets of loud speakers and the third power my subs. I have bought a bass knob so I can put it on the loud speaker amps so I can turn them down. Having loud speakers always loud is a problem. But when I put the knob on the audio cables all three amps are put on the knob... Is there anyway I can have only the two amps on the knob and the third just on all the time? I have even ran two separate audio cables from the radio back to the amps but as soon as the knob is added it puts all three on it. Please help! :-(

kenjancef · 06-02-2009, 08:27 PM

OK, got my amp situation figured out... again...

I just bought a new HU and amp!!! I got an Alpine CDA-9886 and an Alpine MRP-F300 amp. Works like a charm, and sounds GREAT! And I don't get any whine at all, well except maybe from my wallet... but seriously, it sounds preety darn good. I got the amp powering 4 Pioneer 6x8 speakers (model number excapes me at the moment...).

Thanks for all of the replies, you all helped a lot.

Oh, I do have one more question:

I have the amp sitting under my passenger seat, mostly because that is the only spot to put it ( I am an IT consultant and have my vehicle stocked all the time). I am hearing that I should at least mount it on a board or something, right now it just sits on the floor beneath the seat. I have a 2005 Escape, and the amp sits very low under the seat so it gets a lot of ventilation.

What do you guys think? How should I mount it?

Thanks again!!!!!!

Ken

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