I agree with Newbee, if your preamp is new, let the unit and the stock tubes go thru a burn-in period. Otherwise you'll never know the true sound of the preamp and how it integrates into your system.
If you're curious, open it up to see what brand tubes McIntosh has used in your unit. But let the burn-in happen first before tube rolling and during that period you can research the different brands of NOS tubes and their sonic signature.
If you're curious, open it up to see what brand tubes McIntosh has used in your unit. But let the burn-in happen first before tube rolling and during that period you can research the different brands of NOS tubes and their sonic signature.