6688=E180F National UK black plate NOS probably made by Amperex (9ma)

6688=E180F National UK black plate NOS probably made by Amperex

9ma

Gm=13,200

(10,000 hour 9-pin frame grid broadband Pentode, variant is 7737)

- Supratek Chenin, Cortese preamp
- Yamamoto 06-3 2010