There was a “C” amp, with Cinemag transformers, and an “H” amp with Heyboer transformers. Transformers all behave a bit differently from one another, and very much affect the tone of an amp (or for that matter, a mic preamp, recording console, microphone, and many other audio things that need transformers).
For example, the highly-prized vintage Neve preamplifiers were built around Carnhill transformers, a British company.
In any case, transformers add color and character to the tone of audio gear, and unlike some solid state amps, tube amps require transformers in order to pass audio.