[Amps] Cheap auxiliary amp cooling

[GeorgeWallner]

On Fri, 30 Mar 2012 00:29:21 -0700
> Jim Barber <audioguy at q.com> wrote:
<a 250mm (10"!) 12V PC case fan has a
>brushless (no RF noise) DC motor,

Jim,

That sounds like a good fan and it will likely prolong the 
life of you amp. Do not automatically assume, however, 
that "brushless" means no RF noise. The brushless 
commutation is achived using high speed switching 
transistors, which can generate RF. I usually add a .1 uF 
cap across the fan's terminals, a small 2 mH common mode 
choke in series with the 12 V DC power feed and a second 
.1uF cap on the other side of the choke for a perfectly RF 
quiet fan. Sometimes a single cap is enough, but you would 
have to test for that.

73 es GL,

George, AA7JV