<VV> really simple dumb question: coil radio noise suppressor (long answer)

Thu Dec 24 01:22:29 EST 2009

Ray,
Old factory radios had one wire to the speaker and the negative of the
speaker was grounded. Most new modern radios and amps need a positive AND a
negative wire to each speaker. Make sure that neither of those wires touch
ground. Otherwise, you might let the smoke out of your amplifier<SMILE>. Be
careful not to add too many speakers and reduce the impedance lower than the
amp specifications.

As for your stock radio. Depending on which one it is, It probably outputs
positive speaker wires only. If your amp is floating ground, as I guess it
is by your message, you will need to run two wires; positive and negative
from the amp to the front speaker. Many speakers from that era had the
negative of the speaker grounded. You will have to check for that and
correct it as necessary. I recommend replacing the front speaker with a
modern one or two 4-inch. The old stock ones are most likely dried out,
can't handle much power and are usually 10 ohm. The amp won't like them.

 As for two front speakers, I suggest that you buy or make a plate that is
the same shape as your stock speaker and install two 4-inch speakers up in
the dash. That way you can keep the amplifier balanced with the same speaker
load to both left and right. I installed two 4-inch 2-way speakers in the
dash of my 63 Spyder that way. I also installed a 220uf 100V non-polarized
capacitor in line with each positive speaker wire. This makes a high pass
filter and blocks bass so the small speakers don't have to try to reproduce
music below their capability. I have 6X9 2-way speakers in the rear to
produce the bass. All four speakers are fed with a 300 watt 4-channel
amplifier installed under the dash behind the radio, connected to my radio
pre amp outputs. I also installed a stiffening capacitor to help provide
constant power to the amp when I play music loud with the top down on the
freeway. 

As for the engine noise, It can come from several sources. It is always best
to try to fix the problem at the source rather than using a noise filter at
the radio or amp. As the name implies, it is a filter and they usually only
filter out some of the noise. A less than proper sound system installation
can also induce noise.

Now on to fixing your problem. 

First of all, let's check the audio system installation. I will talk about
both modern radios and stock ones for everyone's advantage. Make sure that
both the radio and the amp have good solid grounds. They should also have
their own individual power leads. If you are feeding your amp with low level
pre amp RCA cables, make sure that you use good quality shielded cables.
Make sure that they do not run parallel to any power wires. If you must
cross a power wire, try to do it at right angles. I recommend running the
amp power wire down the driver's side and the radio to amp RCA cables down
the passenger side. If you using a stiffening capacitor, make sure the
ground is solid and not grounded on the same screw as the amp or radio. Be
sure to charge the capacitor properly before turning on the radio. Read the
Capacitor instructions. (I saw one blow up one time). Check that your
antenna is properly grounded to the body where it is mounted up under the
inside of the fender. Verify the power and ground for the satellite radio
adaptor. Make sure that the audio wires from the satellite radio to the
antenna adaptor do not go parallel to any power wires. Is the antenna
adaptor properly grounded? Verify that any speaker wires do not run parallel
to power wires anywhere in the system.

Now that the radio is installed correctly, let's check out the engine.
Usually, if everything under the hood is correct, and the sound system is
properly installed, the engine noise in the sound system will go away.
Besides, the engine will run at its best.

Do you have the woven grounding straps installed at all four corners of the
engine? (For reference, Clark's part number C435R or C435RL) Is your voltage
regulator grounded properly? Are your battery terminals clean and tight? Is
your ground cable properly grounded to both the body and the engine? Are
those connections clean? Are the wires attached to the alternator in good
condition? Inside the distributor, did you follow the Pertronix instructions
and install the plate ground strap securely? Are the low voltage wires on
the coil secure and in good condition? Is you cap and rotor in good
condition? Are your plugs in good condition and properly gaped? You said
that you had Seth's wires. Are you talking about his 8MM plug wires? If so,
are they in good condition? Start the car and look closely at the running
engine in the dark. Slide the rubber disks on the plug wires away from the
shroud. Look for any sparks that you might be having. Check the full length
of each plug wire. DON'T FORGET TO REPLACE THE RUBBER WIRE/SHROUD DISKS
AFTERWORD! Look at the harmonic balancer. Static sparks from a harmonic
balancer can sound the same as ignition noise. Rub some graphite lube on the
balancer to join both parts across the rubber dampener. Look at the rear of
the alternator. If you see any sparks, do what is necessary to fix them. Low
level engine static will be louder when you are using an amplifier on the
sound system.

Check those things and get back to me.

Good luck,

Dave Thompson
Westminster, Ca

-----Original Message-----
From: Ray Rodriguez III [mailto:ravensong13 at verizon.net] 
Sent: Wednesday, December 23, 2009 7:53 AM
To: virtualvairs at corvair.org
Subject: Re: <VV> really simple dumb question: coil radio noise suppressor

Thanks Bill, can you tell me more about this modern noise choke?  Where do 
you install it and where do I get one (radio shack?)

Here is what Ive got....

Original factory FM radio
Signal goes out from this to the rear package tray where I run it through a 
cheap crossover, through a radio shack ground loop radio noise eliminator 
(that knocked it down to 50% of what it was), to a cheap amplifier.
>From that amp the speaker wires go to the four speakers in the rear package

tray and to the one speaker in the factory dash location.

I am using Seth's plug wires

Input to the factory radio is the factory FM antenna and a sattelite radio 
unit with an FM direct adapter.. this automatically disonnects the antenna 
and pipes the signal for the sattelite radio directly into the antenna input

on the factory radio.

I get noise in the speakers as long as the amp is on, even if the radio is 
not on.

The other really odd thing is apparently I only need a single lead for a 
radio signal...  when I disconnect the "negative" speaker wire from the 
crossover input the music still plays just the same.  I noticed the old 
speaker someone had installed in the rear tray had only one wire to the 
radio and the other was connected to ground....

Ray Rodriguez III
Lake Ariel, PA
CORSA member
66' Corsa 140/4 hot rodded coupe
65' Corsa 140/4 coupe under construction

----- Original Message ----- 
From: "Bill Elliott" <corvair at fnader.com>
To: "Ray Rodriguez III" <ravensong13 at verizon.net>
Sent: Wednesday, December 23, 2009 10:28 AM
Subject: Re: <VV> really simple dumb question: coil radio noise suppressor

>I would leave that capacitor disconnected and add a modern noise choke to 
>the stereo system.
>
> Bill
>
> ----- Original Message ----- 
> From: "Ray Rodriguez III" <ravensong13 at verizon.net>
> To: <virtualvairs at corvair.org>
> Sent: Wednesday, December 23, 2009 10:24
> Subject: <VV> really simple dumb question: coil radio noise suppressor
>
>
>>   I just finished installing my Pertronix Ignitor II and the matching 
>> coil in my car (yes I am using 12v Straight, though I havent tapped the 
>> harness for it yet).  I just wanted to check, does the condenser looking 
>> thing on the coil (for radio noise suppression I believe) go to the 
>> positive or negative side of the coil?
>>
>>   Also do these things go bad?  Mine look pretty old and I am having some

>> trouble with ignition noise in my aftermarket amplifier.
>>
>>   Thanks guys, and happy holidays to all!!!
>>
>>   Speaking of holidays, please CC my email address with answers.. thanks 
>> to the holiday my VV inbox is up to almost 1200 messages I haven't had 
>> the chance to sort through yet!!!
>>
>>
>>
>> Ray Rodriguez III
>> Lake Ariel, PA
>> CORSA member
>> 66' Corsa 140/4 hot rodded coupe
>> 65' Corsa 140/4 under construction
>> _______________________________________________
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