Help with a ground loop problem??

[Karl4Cat]

Need some help with a ground loop issue. I just added a Bazooka amplified tube to my stock audiophile system with factory sub. The factory sub helped, but really wasn't nearly enough and the stereo sounded tinny. I'm not really a fan of Bazooka, but the 6.5 unit fit right under the back seat with no issue. I didn't want to loose my console or floor space, so it was my only option. So, I use the factory sub's line in as a source for the tube. Wire everything up and man, is it perfect. Unplug either of the two subs and it's just not the same. They each produce a completely different base type and compliment each other perfectly. Now for the issue. Key off, no problems. Key in the run position, whine from the factory sub. Start the engine and with the volume low or off, a good old fashioned ground loop that fluctuates with the idle. I've tried everything. Different grounding locations. Different power locations. Different remote turn on source. Nothing changes. Unplug the line feed to the Bazooka and the whine stops. I did try an old Radio Shack ground loop isolator which completely eliminated the problem, but also eliminated 50-75% of the bass output of the Bazooka. Not sure why. So, back out it came. Any thoughts on how to solve this?

[ReAX]

Ground loops are a voltage differential between the voltage range at the source and the voltage range at the component, and is usually caused by a poor electrical connection in the body. The easy way to cure them is to add more ground straps or run a ground from the radio/firewall to near the amps ground. You can't have too many ground straps as a rule.

There are a number of causes of inducted noise on the RCAs. The alt produces AC voltage and it's rectified into mostly DC. The mostly DC voltage is filtered by the battery. If the alt is producing very choppy DC current, then the battery has to do more filtering. The battery can still start the engine, but not filter the current well enough. Good RCAs and a good battery can keep most of the noise out.

Since you know the amp/sub isn't making the noise, I would move up stream. Unplug the RCAs from the LOC or radio (however you have them hooked up.) If the noise is still present, then it's in the RCAs and you might try moving them again or getting better quality leads. If it's quiet, then the problem lies further upstream.

[DAVE67FD]

What different "power" locations have you choosen? It seems as your only issue comes with the key on "run" or the engine running. If you truly had only a ground "loop" issue this would typically happen on any occassion (vehicle on or off). although the ground loop would be enhanced or "noticable" when the amp is initiated. I think you could have more of a line noise issue.

ReAX is correct on the alternator inducing AC into the system but the battery in itself has virtually no "filtering" capability. This maybe assumed only by the amount of initial "load" the battery experiences under many circumstances. Typical battery "load" improves regulation of the system.

Todays vehicle voltage regulation systems are pretty well filtered and regulated for the load their designed for. When these systems see larger current loads (even below their "safe" limit) they can begin to exhibit noise.

If your system is direct connected to your battery as i am guessing, you probably need to improve the power line filtering. Their are many available. Check out Crutchfield or others. Noise reduction in some installations can be exhausting. Check the quality/condition of "all" your connections as ReAX stated as well as the grounds. Remember even a good ground can pick-up noise from a "close by" inductive type source (heater/ac blower, fuel pump etc..

[ReAX]

Filtering as in eliminating DC ripple as shown on an oscilloscope. If you loose one of the leads in the coils, the ripple will be bad. A battery smooths out the ripple from the 3 phase rectified DC from the automotive alternator.

I didn't mean voltage or current regulating like a power supply. Thanks for clearing that up.

[AudioNutz]

Where is the head unit grounded?

[Karl4Cat]

As for power sources I've tried using the factory amp's power feed and direct line to the battery with the same result. Right now both amps are on the factory feed, so that eliminates the possibility of the loop being upsteam as the factory amp/sub have no whine alone. Only when I connect the RCA's. As far as signal goes, the factory sub amp is fed a mono signal via two 16 gauge wires in the harness that includes, power, remote turn on, and ground. I tapped those two wires, converted them to an RCA cable, and ran that across under the back seat to the bazooka. What surprises me is that the ground loop isolator worked perfectly, but also cut output of the bazooka by half or so. I thought that would be a quick fix.

[Karl4Cat]

Originally Posted by AudioNutz

Where is the head unit grounded?

Factory head.

[AudioNutz]

There's your ground loop

[Karl4Cat]

Originally Posted by AudioNutz

There's your ground loop

That makes no sense. Factory head with factory amp no loop. Ground new amp to same location now a loop. ????

[AudioNutz]

This is a very common problem.

1. Disconnect the ground at the head unit.
2. Make sure that the head unit is NOT grounded by touching any metal in the dash.
3. Run a 10ga wire for the head unit ground to the location where both amplifiers are grounded. This must be ONE location for all the grounds.

[Karl4Cat]

Originally Posted by AudioNutz

This is a very common problem.

1. Disconnect the ground at the head unit.
2. Make sure that the head unit is NOT grounded by touching any metal in the dash.
3. Run a 10ga wire for the head unit ground to the location where both amplifiers are grounded. This must be ONE location for all the grounds.

I suppose I could try. It seems like a bit much. Never had to do this on any install in the last 20 years of doing these things.Not once. Maybe the ford amp is just super sensitive. Why was there no whine before the second amp was added?

[AudioNutz]

Originally Posted by Karl4Cat

I suppose I could try. It seems like a bit much. Never had to do this on any install in the last 20 years of doing these things.Not once...

Ever make a similar statement to a doctor?

[Karl4Cat]

Originally Posted by AudioNutz

Ever make a similar statement to a doctor?

No. There is usually a cause and effect. Generally do the same thing and get the same result. Never slapped someone and got a thank you. Life is generally predictable. I guess except with Ford factory installed amplifiers.

[AudioNutz]

Car audio noise is certainly unpredictable, and is almost never planned for. I ALWAYS assume that I'm going to have (some) noise, and I ground my head units at the same point that I ground my amplifier(s).

[Karl4Cat]

Now I have to figure out how to pull the wood trim around the radio. Anyone done this? Most vehicles it fits over and around the switch panels and radio. This truck seems to have the panels mounted on top of the trim...