Any one having issues with tubes on mcintosh c-12000 pre-amp

I have the C2700-MAC275, and no i have not had any tube failures yet 2+ years, but mac uses JJ tesla tubes they are ok at best and IMO the first thing you should change after buying a tube mac piece.

I put in some relatively cheap RCA NOS small signal tubes and it was a noticeable improvement. Do your self a favor and buy some better tubes. you don't even need NOS tubes just upgrade from the JJ's. 

I find the stock JJ's to be rather bright, lifeless and flat sounding tubes. They are fairly even from top to bottom though and over all reliable, granted you may have a failure.

You can do much better and some of the larger tube sellers I.e. tube depot, tube store have tube kits at various price ranges each having all the tube you need to re-tube your preamp.

Its good practice to have some spares kicking around for this type of thing. 

I purchased a C2700 about a two years ago and within the first few weeks I had to take it back to the dealer because of a tube bias issue.  They replaced tubes and everything was fine for about 10-12 months than distortion started creeping in again.  This time I replaced the stock tubes with Gold Lion.  I couldn't be happier.