Only as PoC, the input signal is split up into opposing phases before each phase is being amplified by the bjt's that are doing the VCA action, then they are mixed together again in the diff-amp. This will effectively remove the modulating component. Inspiration comes from here: https://www.schmitzbits.de/vtvca.html , but I'm thinking it would be interesting to use nonlinear triodes (ECC85?) instead of pentodes..?
