[Amps] tube cooling

[peter.chadwick at Zarlink.Com]

Ian said

>There are various sources of noise in an air-cooled amp. Bearing and
>blade noise from the blower

Plain bearings are quieter than ball bearings, but generally don't last as
long before they start wearing and get noisy. If you can get 'Oilite'
sleeved bearings, they last pretty well and don't need very frequent
oiling.

Also big blowers running slowly are quieter than small ones run at high
speed for the same back pressure. One tx I've seen had a 3 phase blower
with a rotor about 3 feet in diameter and about 18 inches wide: ran about
1500 rpm and was very quiet. Bearings last longer, too.

73

Peter G3RZP