THE GREAT MULLARD MAGIC BLOG — MESH ANODE

The EF86 audio frequency pentode had been designed for use in high grade resistance coupled AF voltage amplification circuits.  - yes, this pentode was NOT designed as a TV valve as some ill informed naysayers would have you believe. In such circuits any hum and microphony introduced by the valve must be kept to a minimum and the EF86 shows a maximal hum level of 5uV referred to the control grid.  This was achieved by using a bi-filar heater winding and careful internal screening, what, you thought that pin mesh screen was just for looks, oh no!  What's that I...