While I don't own Lamm 2.1 or 1.1, I did own a Lamm LL2 Deluxe preamp, and I installed Mullard Blackburn 6922 with significant positive results.
I expect installing NOS 6922 from Siemens, Amperex or Mullard (depending on your preference) would yield similar results in the 2.1 or 1.1 amplifiers.
I expect installing NOS 6922 from Siemens, Amperex or Mullard (depending on your preference) would yield similar results in the 2.1 or 1.1 amplifiers.

