[joebog1]

I agree with the idea of higher plate voltages making a "better" amplifier. In a recent discussion on 807's (another thread) we "all" agreed that the voltage rating of the 807 was officially upgraded to include the origional williamson design, where it was used as a triode strapped tetrode. I have been using 807's and now some of the variants ( CV428/5B/254 ) for many years and have found them to be like the origional 807's. Essentially indestructable.
( Read between the lines there, and do do the math)
My own attempt at plagiarizing Joseph Marshalls Goldenears amplifier will be my test!. The amp is relatively complex and expensive enough without throwing extra power supplies or screen windings into the argument.
Larger plate voltages also means more expensive filtering components, regardless of what type of filter you require or design. Running 600 volts DC onto the plates would need at least 750 volt rated capacitors, be they electrolytics or PIO's. Better insulation at least for ground shorts means wider thicker insulation for chokes, and for that matter even the HT windings on the power transformer, especially if you use vacuum rectification. At the end of the day it is like everything else ever designed!
1. Today, as we know the number one factor is profit. Expensive doesnt sell well ( mostly) so profit is down.
2> Longevity, or how much warranty do I provide, especially in todays world of "plug'n'play". There are a few other transformer winders on the forum that will attest that making very nice output transformers wont win the lottery, OR let you sleep well!. A really well designed transformer for a specific, exact job can take quite a few hours and the "software" thats blowing around at present is not really best design, more like best practice, taking into account point one. Finding components like onion paper is IDEAL thicknesses is getting very difficult if not impossible. Whatever happened to 7" thou laminations in SiGO steel stampings? 14" thou is available everywhere for cheap, but doesnt make "very good" output transformers. About the best they can achieve is 100KhZ WITH feedback.

I am going to run eight CV428/5B/254 in my amplifier and I will post my build and the end result..

I do have a quick question though G6, WHY do you need at least 75 watts to begin with? A single pair of 807's can do that easily. Forget the slight red plating, thats perfectly normal for 807's.

Just my take.

Regards
Joe