Tony Duell ard at p850ug1.demon.co.uk
Mon Jul 19 15:27:48 CDT 2010

> Tony Duell wrote:
> > 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

I am curious as t owhy toy have output transformers in a pre-amp, but 

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.

> order custom shielded chokes  and power transformers as well as
> shielded 10K to 600 ohm output transformers.

Make your own screens?


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