Tube preamp topologies and music

The radio-transmitter tubes - 211, 805, 845 - require high plate voltages on the order of 1K + volts DC. Building output transformers able to handle a kilo volt without insulation breakdown is difficult. Plus having such a high voltage circuit in a chassis makes it a potential execution device!

Push-pull can have superior signal-to-noise (SNR) ratio and less harmonic distortion due to the self-canceling effect of a balanced circuit. Also there is no DC current flowing in the output transformer of a push-pull circuit. 

AudioXpress magazine had a good article on building a single-end 211 amp some years ago. The authors cautioned that such a project was not for the inexperienced! I suggest you track down this article! I no longer have my copy. Another valuable source of information on tube amp design are the issues of Sound Practices - recommended! Lastly, find issues of Glass Audio - more information on design and construction of tube amps.

Great thanks

A push-pull 211 can have double the power in watts of a PP KT88/6550 amp. With correspondingly more expensive parts/output transformer. Doubling the watts only gives a 3db increase in volume level. Not much!