Stupid stereo question...

So I got my new system all installed and went out to try and setup everything. I have a wicked engine noise in the in-boat speakers only. I went through all the usual checks of RCAs and whatnot. I think I have it narrowed down to a bad RCS cable. If I ohm out the cable it reads a short between the ground and positive terminals. Here's the stupid question... Would this be the cause of the noise? The only thing that has me doubting this is I took the RCAs from my tower speaker amp (which had no speaker noise) and plugged them into the in-boat amp and still got the noise. Could there be something wrong in the amp that would cause noise. For info it is a Kicker IX500.4. Its new and this is the first time it has been powered up.

2 questions.

1. Did you try hooking the tower speakers to the in boat Amp to see if you get noise?

2. How do you have all of your power and ground connected? Is everything going to a single source including the head unit? I had noise problems and when I ran everything straight to the same distribution blocks it all went away.

Another thing to make sure is that your RCA's are far enough away from the power and ground cables

What is considered far enough?

^^^^ Exactly! Yes my RCAs are not running the length of the power cables, but they do cross within a few inches of each other at one spot. Here are some picks of the amp rack to give you an idea of the spacing.


The amp in the middle of this pic is the one I'm having issues with. I'm wondering if having the power ran so close thae end of the amp might be giving issues to.

Your wiring looks pretty good actually. As far as how far is enough typically you would want to run your power and ground on one side and RCA's on the other ( pretty much how you have it). If you have to cross paths try and cross the RCA's perpendicular to the power. In the top photo it looks like your RCA's are kind of jumbled up in and around your power cable.. Maybe try and straighten that out a bit. The power cable directly next to the amp looks fine and probably isn't the problem.

What about your head unit? Where are you getting power for that? If you are powering it from an auxiliary circuit under the dash try tying it directly into the distribution block on your amp board ( both power and ground) and on the power side run both the 12v and ignition wires to the positive terminal.

Another consideration could be the voltage of your batteries. Are they fully charged?

That pic doesn't show it well, but the RCAs are coiled up above the amp rack and the ends that come down are normally not so trashy looking. That pic was taken after I had been troubleshooting my problem and hadn't tucked them back up nicely. The HU and EQ get their power from the factory boat wiring, but technically they are wired to the same battery as the amps since my 3 batteries are wired parallel to each other when the Perko switch is set to "all". I guess I could try actually wiring the HU and EQ to the same batteries the amps are physically wired to and see if it clears up any.

Jason - need to do some isolation. Typically if you have a short in an RCA you end up with some radical screaming noises in the system. But it could be the noise problem. Keeping it simple, I would do the following to isolate and confirm the situation.

- bypass RCA's all tother. take a iPod and 3.5mm -rca cable and plug directly into the amplifier zone in question. If noise goes away, you can eliminate the amp and and everything down stream from there. (make sure your iPod isn't on full volume when you do this test)
- swap RCA's from amp 1 to amp 2. If the noise follows this change, then you know it's isolated .
- Swap outputs from the deck. from front to rear. It may possible you have something happening at the deck itself.

Remember, signal flows from the deck down. So by working your way up stream problems can get flushed out real quick. The nasty ones are when the noise goes away and then comes back 2 days later. Thats when you have a beer and calm down a bit. The points about RCA's next to wire are valid, but your wiring looks good. From your description, I don't suspect the amp I suspect the cable. End game is probably going to be replace defective RCA. Good luck.

-Brian
Exile Audio

Jason,
From your comments it sounds as if you have already eliminated the RCA cable.
Start with no input cable on the amplifier at all. Do you have noise?
If you still have noise then go to the very last component in the signal path which is the speaker and replace it with a temporary substitute. Use only a single speaker and one channel at one time to begin with. Then separately isolate the speaker wiring. For example, all it takes is a single stray strand of wire shorting out downstream from a highpass capacitor that you cannot read with a meter. Keep going upstream in reverse. Then check the amplifier. Every amplifier has a different topology. Kicker can tell you what the impedance relationships should between the RCA above-ground shield and other points such as the primary ground and speaker ground, etc. Keep in mind that the polarity of the positive/ground is probably reversed on one channel. If there is a problem with the amplifier internally causing the pick up of noise you can almost always isolate this with a multimeter before sending the amplifier off for service or a bench check.

David
Earmark Marine

Thanks Brian, I forgot about hooking the iPod directly to the amp. I'm going out there again in just a bit and will try that. I also have a shorter RCA I'm bringing to test a few ideas to see if it goes away as well. I thought the RCA from the HU might be doing it as well and planned on swapping them too. Hopefully by today I can determine if it is my suspected bad RCA or something else and get it fixed. Got to tell you it's a big downer to spend all that time and money to have such a annoying problem.

So did you get it figured out?

Most of my comments were based on you saying you had engine noise, which most times is caused by a ground loop. Do you get the noise when the motor is off too?

I'm a bit closer... David to answer your questions first, there is no noise when the RCAs are disconnected, only when connected and the engine is running so I think everything on the speaker side of the amp is fine. I have determined the amp is good. I hooked my iPod straight to the amp in question and no noise could be heard which gave me a big relief as I was worried about how I ran the power cables near that amp. I ran a quick replacement RCA for testing and the noise was still there. I then installed a noise reduction device my local stereo shop gave me to test with and it helped, but I could still hear a faint audible whine. It was tolerable, but I think I can get it perfect with more investigation.

I woke last night thinking about my RCAs again and don't think I properly checked them properly the first go around and I plan to recheck those tonight. The one common point right now is the EQ I'm using. If my RCA is in fact good then it has to be the signal coming from the EQ to that amp. It is an older unit a friend gave to me a few years back and hasn't given me any issues and I didn't touch it during this latest install, but I keep going back to the idea I'm giving these speakers much more power than ever before and probably had a whine the whole time I just couldn't hear because of lower power. I'm going to recheck the RCAs again and then come up with a way to take the EQ out of the loop. One of those things has to be the issue.

Okay, so I retested my RCAs to find out they are not shorting out so that leaves me with the EQ. I hope to get back out on the water in the next few days to bypass it and see if the noise clears up. I may also make up a jumper wire harness to bring the power for the EQ off the amp distribution blocks to take that out of the equation as well. Hopefully by the end of this week I can have a clean sound again!

I think you are going to find that running all of your power and ground to the same point (both head unit and EQ) will help a lot. I had the exact same problem last year and that is what solved it. Good luck... engine noise SUCKS! let us know

Jason,
Yes, the stereo shop probably gave you a ground loop isolator that interrupts the ground shield with transfomer coupling so DC current that carries the noise can no longer pass between two audio components. However, the flaw in the system still remains. You just installed a bandaid and not a cure. The comments above about a common ground point and common power point closest to the amplifiers for 100 percent of the components in the signal path is very important. 99 percent of the time the engine noise can be traced to the above or to amplifier input gains that are set too high. You can test the EQ just as easily as you tested the amplifier. Plug it in fully operational with no input.

David
Earmark Marine

David do you mean no input to the EQ from either the iPod or HU? I did that this past weekend and still had the noise which means bad EQ or need common power source for all components. Testing proceeds. I will not band-aid it!

Midnightv10 hit the nail on the head! I ran the power and ground for the HU and EQ to my fuse block off the same power as the amp and have no noise now. Being me though I have to know why? Is it just the shorter ground loop instead of going through the factory boat wiring?

A difference in resistance can make for a difference in voltage potential. And the voltage difference will take the least path of resistance. So voltage can flow between audio components in the signal path and through the very shield (even though it is well above ground, it is still the least resistive path) that is intended to isolate the signal from noise. And this DC voltage typically carries noise as a ripple from the alternator and any number of other boat noise sources. Noise is always present in your boat. But you are normally well protected until you introduce a supply or ground loop.

David
Earmark Marine

Yeah... What he said^^^^^
I guess...

Glad you got it solved