"Dave Plowman (News)" wrote in message
...
In article ,
Don Pearce wrote:
In tube power amps, the difference between wide
band and "A" weighted was often found to be 12dB,
and this was, IIRC something of a rule of thumb.

Iain

Such a difference would suggest a great deal of 1/f noise.

Fairly typical of AF valve circuits. Hum.

A common misconception.
With a properly designed PSU C-L-C-R-C and with
attention paid to layout and ground buss, one can build
valve power amps with no hum or thermal noise even EAS
(ear against speaker) And it plays music to please the
most discerning ears.

My 50W PPP tube amp has a noise floor of 80µV
that's -106dB

http://www.kolumbus.fi/iain.churches...em/C50_002.jpg

Iain