OK, I did a test, I unplugged the alternator and took it for a drive. NO NOISE at all, stereo sounded beautiful, so its the alternator that is causing the noise which increases as I go faster. How do I fix it?

I figured I would start a new thread.

 

A filter but listen to richard on the stereo stuff he is top shelf

 

Yes, Richard suggested buying this:
https://www.amazon.com/PAC-SNI-1-Noi.../dp/B000K50HJE

I got one but haven't installed it yet.

 

I had the same problem also with the red GEN light which would get brighter with higher RPMS. Maybe check your fusible link, mine was bad. Was too lazy to repair so bought a one wire alternator and everything is fine.

 

Thanks Bats!!!

Yes- install the ground loop isolator at the back of the radio. Make sure you connect - IIRC it's a brown wire- to the radio's CHASSIS, not the ground wire.

That should solve your problem.

Let us know-

Richard

 

The problem you are having is one of D.C. "ripple" distortion being fed into the power lines by the [pulsing] alternator output. You can install a 'filter'; or you can wire directly to the best D.C. 'filter' known...your battery!!

 

It's AC ripple being introduced into the audio signal- not through the power supply.

IF there was "alternator whine" in the speakers that are powered by the radio- then yes- it would be coming in the power supply of the radio. However "quality" radios have a cap and coil noise filter built-in on the power supply - so does the ORIGINAL radio...see below
So if alternator whine was coming through JUST the radio-a filter and or running the radio power to the battery would be the solution if the Alternator was in good shape.

Radios with "high output"what the OP is running - use what's called a "balanced transfomerless" output- power output can be increased by a factor of nearly 4 by using bridging techniques compared to old conventional radios where the audio and chassis ground are shared. These "newer design" radios- around since the 80's- the speaker cannot be grounded and are less susceptible to "alternator whine."



The seperate amplifier (Rockford in the OP case)- does something COMPLETELY different- it takes the DC power 12 volts- converts it to AC ( done by a high speed switching circuit) THEN uses a transformer to raise the voltage- then it's converted back to DC. Often referred to as a DC-DC converter. The voltage is probably somewhere in the neighborhood of 40 volts DC.

So the AC ripple coming INTO the Amplifier via the DC power source - is cleaned - converted to AC and cleaned again when its converted back to DC. That's why I'm suggesting a simple filter on the power supply will not solve the problem at hand.


Richard


Dark red capacitor -acts a high pass filter. And the brown coiled wire acts a lowpass filter. Both "clean up" the DC going into the radio.

 

Well I did the install of the filter you had me buy, it helped a little at low RPM but at high RPM the noise comes back. Should I have the radio re-grounded to the frame or put a suppressor on the alternator? Also the power and RCA cables are running right next to each other, would that be a problem. Maybe the same kind of filter on the amp side, I got two. I'm at a loss with all the info. Thanks!

 

Hmmmm.....didn't fix it, eh?

Might want to try something else......

 

Fixed it some, need suggestions, should I do any of the ones I mentioned?

 

How did you ground the ground loop isolator? Directly to the radio's chassis- and did you try to the car's ground or did you try to not ground at all?


I also suggested better RCA cables- and the power wire next to them could DEFINITELY cause a problem. A few inches away is all that's needed.

Like I said - get a good pair of RCA cables and run them front to back- see what happens.

Richard

 

Thanks Richard. I tried both ways, tap to ground and the radio. Like I said it is a little better. I'm taking it to the stereo shop Sat. and have them run better wires away from the power from the amp. I'm also going to have them ground the radio to the frame, I couldn't see where it was going to.

 

Good luck-

The Corvette's are a 'noisy' car by design-

As the alternator is up front and the end of the "electrical line" and the battery is in back on the other end of the "electrical line."

Since it did make an improvement - you are on the right track- I would try the RCA cables first.

Richard

 

Good luck at 'throwing money' at a problem which has a simple fix.....

 

7T1,

Its not costing me anything, the shop guaranty's the work. When its there I am going to have them run the power and ground to the battery, Why do it myself when they can do it for free. Someone mentioned to ground the alternator to the frame, just did that because it was easy but it didn't work.

 

Its Finally fixed! I want to thank Richard454 and 7t2vette for their suggestions. I brought it back to the shop and they didn't know what to do. By taking richard454 and 7t2's suggestions I told them to upgrade the RCA's and run it on the passenger side. I then told them to run a power and ground from the radio to the battery on the drivers side. I put power filters on the radio on the red and yellow wires and a filter on the RCA wire. I had to tell them to do this, they had no clue. I tested in all RPM ranges and no noise from the alternator. Thanks to this great forum!

 

Hey, that's OK. I do it all the time!


Seriously, good on you for finding the alternator as a possible single source for the noise. As mentioned by Richard, these fiberglass cars really do let Ignition RF go wherever it wants to go. Did I miss you mentioning the Ignition Shielding was mounted on the engine? That makes a HUGE difference in audio quality.

Good luck.
Steve

 

nope no ignition shield, I have HEI distributor, doesn't fit.

 

You did what I had to do and I even have the shield. Everything went to the battery and I went a step further and made the ignition wire go to a relay.

 

My HEI Distributor might be different than yours. It's a tight fit now, no question about that. But if I operate the engine without it, I can forget about listening to the radio. I also run 10mm Plug Wires on this 383 I built up, and although tight, everything fits in all of the shielding.

Are you sure you can't bend/open up the Distributor Box a little? I had to, and I've got a clear radio now. The big Air Cleaner I have almost touches the Box, but that's really the only other concern.
Don't quit.

Steve