Peavey Windsor100 head power section 6550 mod...

[jim p]

Relative to which transformer would be better I can’t say. I haven’t used either one and the specifications don’t give enough detail to say one way or the other. If you go by the heaver the better for bass you would need to find out the weight of the one they have at Triode electronics. The one they sell at Triode is probably made by Magnetic components and as far as I know they make good transformers that people are happy with. As far as the ultra linear connections if you look at the schematic for the transformer at Triode http://triodeel.com/dynacoa451.jpg there are five taps. The plate supply goes to the red wire, Blue/white to one set of plates with green/white to their screen grids. Then blue goes to the other set of plates with green to their screen grids. The screen grid taps on the transformer are at 40% of the windings for each set of tubes. If you look at the data sheet for the 6550 http://www.mif.pg.gda.pl/homepages/f...35/6/6550A.pdf they have tables of the specifications for both pentode and ultra linear along with static curves. The plate impedance of an ultra linear amp is lower than a pentode due to the feedback created by connection of the screen grids to the output transformer. With lower primary impedance (Plate) the amplifier will not be affected by the changing impedance of the speaker as much so less distortion. There is a very large change in the impedance of a speaker in the range of 80-120 Hz due to the resonance of the speaker. The resonance is relative to the damping due to its surround and the added damping relative to the speaker enclosure. Also the impedance of a speaker is very low outside of resonance at the low frequencies. An 8 ohm speaker is 8 ohms at 1 kHz due to inductance it is less than 8 ohms at say 200Hz and more than 8 ohms at 2 kHz. By the data sheet the power output with ultra linear and pentode connections are almost the same.

[ttenroc]

So with that info I can hypothetically just replace the OT in my current set up, without changing the tube arrangement, and have clean power with my amp dimed?
I was intrigued by the output power of the 8417 tubes on the link you posted( http://www.mif.pg.gda.pl/homepages/f...168/8/8417.pdf )so I did some looking into those as an option. turns out they are very rare and expensive, but folks are suggesting tungsol KT120's as a replacement. http://www.tubedepot.com/ts-kt120.html
Looks like a pair of KT120's can put out 150 watts under the right circumstances. Do you think I safely can use a pair of them in my Windsor?