Prima Donnas: 2x56 -

Older tubes drift. Check your voltages every few months to ensure they stay in the "sweet spot."

Much like a difficult opera singer, the 56 tube requires a perfect environment to perform. But when the bias is right and the shielding is perfect, the vocal reproduction is unparalleled. The Technical Specs Prima Donnas: 2x56

Use tube dampers or high-mass isolation platforms to combat microphonics. Older tubes drift

The 56 is famous for creating a 3D "bubble" of sound. Prima Donnas: 2x56

If you ever have the chance to sit in front of a 2x56 driven system, prepare for a "time machine" experience.

It features a distinct "shoulder" glass shape (S-12 or ST-12).

Always use a soft-start circuit to protect those precious 1930s filaments.