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When i was 15 i built 50 watt CW transmitter from the schematic published in a Heathkit catalog, then decided to Heising-modulate it (plate modulate the final) for voice. Used a pair of 25 cycle TV power transformers hooked back-to-back (primary to primary), with the HV winding of the first tranny run by push-pull 6L6s, and the HV winding of the second tranny in series with B+ feeding the RF final stage (two 6DQ6s in parallel). The trannys had pretty sharp rolloff above 5 kc (kilocycles in those days), ideal for voice while keeping the bandwidth tight. The modulator was on a separate chassis from the transmitter, with its own power supply.
At that age i didn't understand about core saturation but apparently the big trannys avoided it, as the rig ran spectacularly well and the modulation envelope scoped at 70% with no sign of clipping.
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