Offering unmatched warmth and clarity, the U99 is a classic tube and transformer design. The U99 features a hand-made European 1" diameter dual back plate, dual membrane capsule. Each hand-tuned capsule uses 6 micron Mylar specially selected for consistent thickness and is sputtered with a unique blend of gold and aluminum for excellent transient response and long life. The back plate design is from the KK67 family. The electronics feature an EF86 tube run as a triode.