Second filament winding on power trany

[gravitylow]

I am building an 18watt head and have a set of tranies for a 20watt from Mercury Magnetics. I just realized that there is no second filament winding for the rectifier as there was for the 18watt. Why does the retifier have it's own winding? I'm guessing it is to reduce hum from the power supply. Can I use the single winding for rectifier and amplifier tubes? What is the down side of doing this?

Thanks

[101456]

You could also choose for a Weber Copper Cap. I've heard they reproduce the tube rectifier sound quite good, and they don't have a fillament!

http://www.webervst.com/ccapord.html

Good luck!

[markh]

Historically, the reason for the second winding is for safety. If the tube rectifier failed with an internal short to the heater, the rest of the tube heaters wouldn't see the full B+ (given a second heater winding).

In practice, I've never heard of this happening.

--mark