push pull cathodes connected through output transformer?

[thetragichero]

amp chassis came out of a trashed webcor  'fonograph' and i have never seen this before. help me understand why and what it does.... is it a similar idea (localized negative feedback) to ultralinear? any benefit in a guitar amp?

[tubeswell]

The winding attached to each 6V6 cathode provides a small amount of cathode current feedback (negative feedback), which helps improve  fidelity across bandwidth. The 270R resistor on the CT of this winding is for cathode biasing. Other than that the OT functions in a conventional way (not UL).

[thetragichero]

cool!
and thank you

[thetragichero]

also for anyone googling webcor mt-1655 power transformer in the future: the ht and heater center taps on mine don't have wires coming out of it. thought maybe it was missing and was googling how in the hail it used a full wave tube rectifier without a center tap but it turns out the transformer shell itself is connected to the center taps internally. i will be attaching a wire to the bell because i don't rely on transformer bolts for important ground contacts

[pdf64]

The Leslie 147 uses a similar idea but, by use of a CT secondary winding and using it in a balanced arrangement, avoids the need for a super fancy OT http://www.captain-foldback.com/Leslie_sub/Leslie_schematics/147.GIF