Curriemt - Microphonics are relative. If you have microphonic tubes there is no helping the situation other than to replace the tubes. I'd suspect that was the problem with your Cortese. The Cortese is solid.
But...
Because of it's point to point, solid core wiring and relatively thin chassis, I could see how the Cortese might be considered more microphonic because those elements can exacerbate microphonic tubes when compared to something with a PC board like your Janus - or others.
Without getting too in-depth - I might say, the Janus, Rhea and Calypso have their own set of issues to keep owners and dealers quite busy. So much so that my dealer stopped carrying them.
But...
Because of it's point to point, solid core wiring and relatively thin chassis, I could see how the Cortese might be considered more microphonic because those elements can exacerbate microphonic tubes when compared to something with a PC board like your Janus - or others.
Without getting too in-depth - I might say, the Janus, Rhea and Calypso have their own set of issues to keep owners and dealers quite busy. So much so that my dealer stopped carrying them.