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Jim Yanik

Kripton wrote in :

On 2012-01-21 18:55:59 +0100, said:

On Sat, 21 Jan 2012 05:27:16 -0800, "William Sommerwerck"
wrote:

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

Exactly! I have a bunch of 1N4003's in my junk box that I used for
any project needing a general purpose diode that can handle some
power.

you mention it : the voltage of a car battery varies ...
from 14v to 12v or less
does the boom box handle 10v to 8v ? or not ?
that's why a regulator is needed, except if a regulation is made inside
the boom box ?
who knows...

you also need FILTERING to reduce ripple(and noise);
auto alternators do NOT output straight DC,but pulsating DC.

A regulator IC will reject a lot of ripple and noise.
a string of diodes will not.

but hey,it's your boom box.(and ears)

--
Jim Yanik
jyanik
at
localnet
dot com