Edward Schernau wrote:
> I'm hooking up a rig to run my cheapo speakers off my +12V supply.
> I have a BP6, very stable at 94MHz, and a 250W PS.
>
> I'm getting amazing amounts of audio noise from the speakers
> when powering them through the internal drive-connector (+12v) line.
>
> I placed a BFC (Big Capacitor) across the lines, to no avail. Any
> way around this?
Electronics 101:
Put an inductor before the cap.
The size depends on the amount of current you're drawing at the
speakers side. Be careful, an inductor/cap circuit could oscilate. I'm
not sure how to normally prevents this. In the circuits that I've seen
they don't do anything extra. A resistor in series with the inductor
should do the trick, but it seems the parasitic resistance there is
normally enough.
If the current you draw is small enough a resistor can take the place
of the inductor. Calculate "R * C" to be well larger than 20
microseconds (50kHz). (But the larger the R, the less current you can
use.)
Roger.
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