Laptop external power from batteries (DC/DC)

[VirginSnow at vfemail.net]

> Date: Mon, 18 Aug 2008 20:50:35 -0400
> From: "Ben Scott" <dragonhawk at gmail.com>

> multi-voltage adapters).  Nasty alternator noise in the audio.   Went

>   I imagine sufficiently good quality components would not have
> trouble, but most laptops have cheap parts for both power and audio.

Noise depends on the converter technology you're using.  Inverters
(which use AC) and DC-DC converters (rapid switching) both generate a
lot of noise.  Converters based on voltage regulators generate much
less noise... but they're only about 30% efficient.  So you can get a
nice, clean, power supply in your car.  You just have to use 4X the
power and throw away 3/4 of it.