anyone use KT120's or KT110's tubes in MAC 275 ?

In the KT88 compatibility test performed by Fluxion audio technology, it was concluded that If an amplifier is designed for KT88 in the case of mc275; KT120 is interchangeable without any circuit modification and bias adjustment. 

https://www.youtube.com/watch?v=1iR3bXLVSbY
https://www.youtube.com/watch?v=jhfpVs9gtaQ

Check with McIntosh regarding the use of KT-120's in your Mc275. The KT-120 will sound different depending on the amp, speakers, etc.

It would contact McIntosh regarding your question.

Also, I do not like KT120s either. Too much bass, grainy, dull... really not a good tube. I put my Gold Lion KT88s back in my amps and never looked back. From what I have been told the KT150s are no better.

thanks XTil6, my mistake on the kt110 was thinking of the ARC ref110 amp.

Never heard of a KT110. Did you mean a KT150?
FWIW I do not care for the KT120's. Too forward and a bit bright for my taste. I have an Octave V110 which is designed for KT120's.