19 Jul
2010
19 Jul
'10
10:27 p.m.
Tony Duell wrote:
I am curious as t owhy toy have output transformers in a pre-amp, but
anyway.
Have you treid moving them around. If they're of the normal clamp
construciton, arranging the cores in a straight line is about the wrst
thing you can do. Turning the mains transofrmer through 90 degress might
well help.
Certainly for testing. RRun the heaters off a
battery. If the hum goes
away, at least you know where it's coming from.
I found my hum ... Poor
magnetic shielding between the power supply
and the pre-amp output transformers. Not much I can do unless I can order custom shielded chokes and power transformers
as well as
shielded 10K to 600 ohm output transformers.
Make your own screens?
-tony