TECHNICAL DATA TAD EF86 / 6267 Premium Select Low Noise AF Pentode The TAD™ EF86 / 6267: is a glass envelope miniature pentode for highquality small signal amplification in sensitive input stages The TAD™ EF86 / 6267 is likewise suitable for many High-End-Audio devices and microphone preamps as well as the famous VOX AC amplifier line from the early 60´s. The TAD™ EF86 / 6267 is a faithful reproduction in shape and tone of yesteryears EF86´s. Characteristics of a bogey tube: Electrical Heater.