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

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.

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

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.

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.

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