Rick, the original 275's had two 12BH7 slots and had a total of 8 twelve volt tubes. As the 275 changed throughout the years (1961), it has been redesigned, to only have 7 twelve volt tubes & to have just 12AT7's and AX7's.
McIntosh MC275 original amplifier
Category: Amplifiers
My system consists of an Original McIntosh MC275, Placette passive pre amp(3 input model)Oracle Delphi turntable,Grace 707 tonearm with custom phono cable, Denon 301 II MC cartridge,three different cd players,Klipschorn and Focus 20/20 speakers(depending on my mood)various power conditioners and two Blue Circle BC86 MKIII power line pillows. After trying many different tubes I finally found a combination that works to my satisfaction. If you have any suggestions or comments, I am open to hear them. I use 4 Genelex KT88 power tubes,one Amperex 12ax7,two RCA 5814a Black Plates,two RCA 12BH7A and two Telefunken 801S tubes. It took this combination of tubes to really get my amp to sing the way I think it should. Obviously the Telefunkens were great, but the biggest surprise to me where the inexpensive RCA 5814A Black Plate tubes in the 12AU7 sockets. By the way the Telefunkens are in the 12AZ7 sockets.
My system consists of an Original McIntosh MC275, Placette passive pre amp(3 input model)Oracle Delphi turntable,Grace 707 tonearm with custom phono cable, Denon 301 II MC cartridge,three different cd players,Klipschorn and Focus 20/20 speakers(depending on my mood)various power conditioners and two Blue Circle BC86 MKIII power line pillows. After trying many different tubes I finally found a combination that works to my satisfaction. If you have any suggestions or comments, I am open to hear them. I use 4 Genelex KT88 power tubes,one Amperex 12ax7,two RCA 5814a Black Plates,two RCA 12BH7A and two Telefunken 801S tubes. It took this combination of tubes to really get my amp to sing the way I think it should. Obviously the Telefunkens were great, but the biggest surprise to me where the inexpensive RCA 5814A Black Plate tubes in the 12AU7 sockets. By the way the Telefunkens are in the 12AZ7 sockets.