Roger and Ed,
If you want to get fancy you could do a pie filter:
DC in - L1 - L2 - L3 - Filtered DC out
| |
C1 C2
| |
Ground
As Roger pointed out the bigger the L's and C's the less ripple. Also,
as Roger said, oscillation could get you. The LC has a resonant
frequency but the bigger the L's and C's the lower it is. I would still
check the grounding for the speakers and remeber the the inverse square
law. The further away the speakers the lower the signal (i.e. signal
drops off by the square of the distance). Also, is the BP6 in a good
grounded case to reduce EMF?
Eldon
Rogier Wolff wrote:
>
> 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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