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Discussion Starter #1
Well, I brought home an oscilloscope last night and decided to poke around my stereo amplifiers to see what type of noise was on the 12 volt line (I've got alternator noise on the speakers, with the stereo/amps on and the volume at minimum).

Set the engine speed at 1200 RPM (via fast idle cam). Measured a 50 milli-volt peak waveform occurring at 85 hertz. I used my old hood pin as a core. I wound about 6 feet of AWG 12 solid core wire (pulled a piece out of some spare ROMEX that I used to wire up my fluorescent lights in the Garage. This statement is simply here to provide support for my packrat tendencies - hehehe).

Wired the 'coil' in series with the power line to the amps and the alternator when appeared to be less, but still there. On the scope, I noticed that I rounded off the spikes of the primary component, and reduced the amplitude a little, but apparently not enough to get rid of it.

It now appears time for me to do some more research on this subject. At one time (many moons ago) I could probably have been able to construct a coil that would remove this noise from memory, but that was many, many beers ago.

Next step is to measure the noise at the input to the speakers and compare.


Steve Leslie, 65 coupe in restoration. 302, toploader, A/C, disc brakes, bench seat

http://albums.photopoint.com/j/View?u=1571478&a=12535662&p=46267978&Sequence=1.jpg
 

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Forgetting what you do for a living for a moment....Why wouldn't you wire in noise suppressors (assuming you haven't)? You can suppress the power to the amps, as well as the coax. signal line to (or from) your head unit to the amps. Sounds easier to me, and the suppresors have always worked for me in the past.

Shannon a.k.a. The ShanMan! /forums/images/icons/cool.gif
66' Vintage Burgundy C-code coupe
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Discussion Starter #3
Heavn't found any noise suppressors that can handle 80 (total), much less 40 amps (per amplifier). That is why. Plus, it's phun! I actually have located a 100 amp noise suppressor from a marine supplier (I think it is for yachts) But wanted to collect some info prior to talking to those people.




Steve Leslie, 65 coupe in restoration. 302, toploader, A/C, disc brakes, bench seat

http://albums.photopoint.com/j/View?u=1571478&a=12535662&p=46267978&Sequence=1.jpg
 
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