???
Never heard that one before. Added microphonics? Like as in a ringing microphonic pre tube?
I’ve had a few Jubilee 2554 combos over the years; a black tolex 1988 version was my main gig amp for 5 yrs. Not one hint of microphonics, ever. Mostly hooked up to a G12 65 cab though; only time I used it as a standalone combo was at home for low volume practice.