Any tubes that came stock with it are junk, sorry to be so blunt.And McIntosh runs there tubes hot! You might get 2-3k hours if your lucky with stock tubes. Call Andy @vintagetubeservices.com 616-454-3467, And be patient, Andy is old school and he knows his shit when it comes to NOS (new OLD stock) or OLD original tubes that will sound better. Try some REAL mullard 12ax7's or 12at7's or Amperex ECC83's or ECC81's.You will be astonished at what a difference a good pair of these little guys can do for your sound. Tube roll its fun!