If the output transformer come with ultra-linear taps, they can used by cross-coupling the taps the screens via a coupling capacitor. This arrangement offers the advantage of using a lower screen voltage than the plate voltage. A lower screen voltage is easier on the tube and it allows to use tubes such as the EL509 that have a much lower maximum screen rating than the plate.

     In the circuit above, two output transformers are used (here is a use for old Stereo-70s) and the 33% ultra-linear taps are cross-coupled so as to yield 33% of the entire primary to the output tubes. In a Class-B amplifier, each output tube sees one fourth of the primary winding's impedance, but in this circuit, each output tube sees the full primary impedance even in Class-B, thus the need to cross-couple.
     Speaking of the Dynaco ST-70, this amplifier would make an excellent test bench for the following idea. The stereo amplifier's two output transformers and four EL34s can be used to create a mono-block amplifier. Because the output tubes are nested in between two output transformers, the PSRR of this setup is -6 dB. In other words,  half of what noise appears at the top transformer's center-tap is present at the EL34's cathode. This halving results from the to transformer secondaries defining a 50% voltage divider, as each reflects the same impedance from the load impedance. Thus, the output tubes need to see half of the power supply noise at their grids as well, if the power supply noise is not to be amplified.

     Alternatively, two output transformers can be used in place of the transformer/choke combination. The outputs are wired in parallel and the cathodes and plates see the same load impedance. A choke might be needed to decouple the power supply. (Without this choke, it might be difficult to ensure that the whole of the primaries are always fully loaded because of the short circuiting through the power supply. In theory, the choke is unnecessary, as center-taps do not move. Experimentation is required. Experimentation is all important. Unlike the glossy audiophile magazines, this journal does not present circuits as pre-masticated packages, shrink-wrapped, glossy, with no thought required. Of course, thought-free circuits is want the majority of audiophiles want, but the readers are of this journal are a breed apart. A voltage meter and function generator are enough to perform numerous tests on tube circuits, while adding an oscilloscope is even more helpful.) 

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