Vari Mu compressor without input transformer

[kambo]

dont know the technical reason, and it may not apply to ur design, but
when i was working on my tube mixer, i had hum on one deign idea,  i added cathode follower,  and hum disappeared completely.
also, keeping all crocodile cables inside the enclosure were helping  a lot with hum levels when messing around!

 

[abbey road d enfer]

The negative side of cathode CV obviously is the large current needed for CV but I think it's worth it. Good input transformers are expensive and with cathode CV it can be replaced with cheap fairly simple circuit.

If your opamps have enough voltage (and current) swing to drive the cathodes, they are suitable for grid-drive. The signal AC component is much smaller than the bias swing. And there are ways to increase the voltage swing, like floating rails.
I don't think tehre's any significant virtue in cathode-drive, but then you could do that Music Man fashion, with a power transistor driven by an opamp.