| > I have a '66 Midget that's still Positive Ground. The previous owner did a
> dandy job of installing a voltage inverter for a rather nice pull-out
> stereo - that I still have. It's true, the voltage inverter puts our a
> whine. 
The older converters use a low (audible) switching frequency. If the output was 
not filtered with a large enough capacitor the voltage ripple from the 
converter could be heard through the radio. With the advent of high speed 
electronic switching DC-DC converters the switching frequency is up to 300 Khz. 
Normal hearing is 20 Hz to 20 kHz.
Comments Welcome!
- -Mark
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