Radio Noise after Upgrade

Q: Radio Noise after Upgrade

A: During my college years after GM, I installed over 100 car stereos working at a shop and on my own and noise was all too common. I warned anyone thinking about installing an “amped” system that this would be a problem, and it usually was. The secret to eliminating noise is to eliminate resistance in power and ground and in signal distribution. Resistance points act as an antenna for noise. Isolate the power and ground from other systems in the car. Circuits sharing the “ground buss” tend to emanate crap onto the ground (chassis) and power lines. Even the best filtering won’t get rid of it. Garbage in, garbage out!

1. You get what you pay for! Cheap amps like the ones they sell at Radio Shack will whine and pop. Use quality products. Sony has some of the best filtering in their power supply inputs.

2. For amps and accessories such as a CD player mounted in the trunk. Use heavy gauge stranded wire from the battery (protected by a circuit breaker at the battery), twisted with a battery return line, and surrounded in braided shielding grounded at both ends. Avoid grounding the amp to the chassis.

3. Your in-dash unit and equalizer should be on a dedicated power circuit as well. Bring in a shielded power and ground from the battery as well after the circuit breaker. Switch the power on/off using a separate 12V relay operated by the original radio power source.

Once you clean up the power delivery problems, move on to the signal distribution.

4. Too much hype off of gold plated RCA connectors. It’s true, gold is the best conductor. However, in my tests with a spectrum analyzer I’ve found that a good quality connector, one that provides good contact between the shield of the jack and plug, makes no difference. It’s a signal with very low current and therefore very little chance of voltage drop due to current. Use very good braided shielded wire between the dash and the amp. I make my own custom RCA cables using teflon covered RG178 coaxial cable (not TV antenna wire – it’s too big but will work if you can’t get the small RG178).

5. Speakers located near the amp need not have shielded wire. It’s a good practice to shield speaker wires servicing doors, kick panels, or anywhere near the firewall.

6. As far as fidelity in a convertible goes, make sure the speakers are in an enclosed chamber like a speaker box, such that sound that travels backward in the speaker is reflected forward. The highs are going to get lost unless you mount tweeters next to your ears.

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