I have a whole bunch of stereo questions after a recent install. I often see people with similar questions refered to the stereo forum. I can't find a dedicated stereo forum on this site? Is there one on this site? If not is there a particular site someone would recomend? Thanks and excuse my Attention Deficit Disorder.

 

http://forums.corvetteforum.com/audio-electronics-20/

 

I looked at this link but most of these are on C4's or newer.
what questions did you have?

 

I have a 70 convertible. Replaced a perfectly good kenwood stereo with an alpine head unit and a rockford fosgate four channel amp. Had to change head unit because the basic kenwood would not accommodate a four channel amp. Had it installed at the stereo shop 'cause I was involved in other projects. Every part of the system sounds good, cd, mp3,i-pod, except the am/fm. I thought WHO CARES if the am/fm doesn't work with the other options but I can't stop obsessing and don't want this to beat me. I should tell you that the previous owner glassed over the antenna hole and just cut off the antenna and twist tied it to the frame. It worked fine with the Kenwood. Now I have engine noise when I listen to fm. I know conventional wisdom would say punch a new hole, use a well grounded antenna and be done. I would be willing to do that if I hadn't had success with the Kenwood. I have an msd 6al ignition and was advised by someone on this forum that they solved their problem with a msd capacitor. It did not work for me. I've tried aftermarket antennas,well grounded, and it didn't work. I've disconnected the alternator both at the connections and the belt, no luck. The stereo store replaced the head unit, no luck. I grounded the stereo directly to the frame, no luck. My plug wires are correct and couldn't locate any jump in the spark with a screwdriver or see any in the dark. I double checked my battery ground and made a new engine-to-frame ground. I can get the station but I have this engine interference. I'm pretty sure that it changes with rpm's but can't be positive because the hedders are loud and it's a convertible. I think I could go on and on but I won't. Any thoughts? Sorry about this long post. I'm getting a drink

 

It sounds like what you're talking about is a ground loop. I'm assuming it's not there when the engine is off.

It may have shown up with the kenwood were it attached to an amp.

Try hooking them all to the same ground and see what happens.

Good luck!

 

Check the RCA cables for improper grounding. The outer shield is frequently ends up as a ground.

http://forums.corvetteforum.com/c3-t...ker-setup.html

HIH
Mooser

 

So to fill this recomendation would you advise to move the radio ground to the battery which is where the amp is grounded?

 

Yes, try that and also follow the advice Mooser is recommending, that will likely help as well.

 

Buy one of those rare, steel-bodied Corvettes and you won't have this problem. I gave up on listening to AM/FM in my car. Not a solution, but at least I have closure.

If it were me, I would ground both amp and radio to the frame, if possible. I have my wires run to the cargo area and through a hole in the floor and then to the frame, but that's on a C2.

 

My truck has sirius radio. I pick the station and NO commercials.I have never thought once about listening to fm. Now that I can't have it in my corvette it is the most important thing in the world to me.Kind of sad huh?

 

I have not yet had a chance to try the fixes that I have been given. I am going to take the seats out to gain full access to to back where the speakers and amp are located. I am also making a list of suggestions and am going to carry them out in some sort of logical order. I have seen in previuos posts where people have hooked their i-pods directly to the amp. Some did it for diagnostic purposes and others to avoid the head unit, I think. How do you hook an I pod directly to the amp? What do you gain or learn from doing this?

 

You do not say if the engine noise sounds like alternator whine(you did say that you disconnected belt to it) or spark plug type noise that increases and decreases with engine RPM.

Are you running resistor or non-resistor spark plugs,,,,proper spark plug wires are not always enough.

Have you tried filters in the power lines to the head unit or the amp?

Is the noise being radiated/broadcast thru the air or thru the wiring. A portable am/fm radio playing in the car and moving it around could give you a clue.

If alternator whine, a capacitor on the alternator to ground solved that for me on my 71 which has a an excellent audio system.

On my 71 with an MSD system, I use the 1970 Corvette distributor shield box, instead of the 1971 much more limited protection box.

Try disconnecting the MSD unit and run only off coil. You can do this with jumper wires on coil if you've installed the entire MSD package of components. This bypasses the MSD box. Does problem go away or lessened?

Of course you will never get as strong a radio signal into your head unit if not running an external antenna. With the weaker signal, you must crank up the radio volume higher,,,,which merely cranks up everything, the engine noise and the radio signal, so your signal to noise ratio does not change. Your old unit may have had circuitry that is more discriminatory in screening out the engine noise than your new unit,,,however again a high quality inline power filter could help much. I suspect that there may be tunable filters but have never found a need for one,,,,but you might look for one.

Have you tried one of these so called portable antenna's that plug into your radio and are just a basic long piece of wiring, instead of using your chassis as an antenna? They can work ok for FM, but are not of much use for AM. I have no antenna on my 59 and have used such for my head unit for FM. Might be using one of these and routing properly in the car could solve the problem

You mentioned using an MSD ignition capacitor,,,is this one that runs off your coil to ground. If not you might try one there.

Is it possible to get some type of foil or or some such, between your radio and your engine.

Experimentation is the key. Fiberglass cars are sometimes difficult,,,GM found this out early on.

A good flush mount power antenna would not look to bad.

Forget fm, enjoy your ipod. Even in my regular cars, I listen to fm about once a year,,,,if any radio in cars, its usually am talk shows or sports.

 

I don't think you gain a whole lot. You get a headphone->rca cable and plug it in to the inputs. I guess that will tell you if you have some weird grounding issue at the amp, but it doesn't help isolate RCA cables or head-unit chassis ground issues.

 

I'm sorry, were you talking to me? I was distracted looking at that girl in the picture I suppose if I had to say I would call it alternator whine athough my hedders are so loud I can't say for sure that speeds up with the rpms. Have not ruled out that it could be secondary ignition interference either. My spark plugs are shielded. I have not tried filters in the power lines mostly because others here have said it negates the purpose of the amp,if I remember correctly. Also the stereo store where I had it installed and radio shack don't carry them so I guess I would be stuck with internet stuff and their wild claims. Any suggestions? I tried a capacitor on the alternator and at one time had the alternator belt off and wiring disconnected but still had the noise. At that time I decided I might have grounding issues or ignition noise and changed gears, so to speak. I'm pretty sure the msd capacitor ran from coil to ground. It's between the box and the coil or between the box and the didtributor. If it's not coil groung I will try that also. We tried foil and sheet metal and nothing changed. I tried the hidaway antennas, powered antennas , masted antennas with their own cables...NO CHANGE. I do agree that an stock style grounded antenna would not look bad. Don't know if it would solve my problem but it would give me a place to put an American flag. Thanks for your advise. Matt

 

I contemplated that but I know there are those who swear you have to keep the ground short. I figure it would be a run of seven or eight feet total from amp to frame. I would be interested to hear from someone with a long run like mine who sais it's not a problem. Thanks

 

Was having alternator noise on my system.Instead of using the head units RCA output to the amp I used line-out converters to the amp.Result was no more buzzing over the speakers. I did try grounding this and that but nothing worked.I have a Crane HI6 ignition box with the recommended capacitor installed per instructions.System is now buzz free.Can't remember if it was just buzzing on am/fm and or C/D use.Good Luck....