EF86 EF86 / 6267 Pentode Vacuum Tube

The EF86 (6267) is a small-signal pentode designed specifically for low-noise audio preamplifier service, with an internal shielding structure that minimizes hum and microphonics. It was the standard first-stage tube in high-end European hi-fi preamps and is the V1 tube in the Vox AC15 and AC30 Top Boost channels, defining their chimey, three-dimensional clean tone. With a voltage gain of approximately 200 in typical pentode operation, it provides more amplification than any dual triode but demands careful mechanical mounting to control microphonics. Mullard, Telefunken, and Amperex are the sought-after NOS makes; the tube's sensitivity to vibration remains its principal practical challenge in guitar amplifier service.