1 slightly microphonic low noise tube) 5687 Raytheon black plates NOS "square" getter halo mid-1950's 

1 section) 37ma Gm=11,300

1 section) 39ma Gm=11,800

microphonics are low, only slight thump when tapping on tube in circuit

Recommended for

Manley

Modwright

Audio Note

Ray Samuels

Ayon

Kondo

Mastersound

Audio Thrills

Loth