THE GREAT MULLARD MAGIC BLOG — df66

Now then, everyone tends to think of Hivac when they think of miniature valves for hearing aids but Mullard made them too.   Hearing aid valves were specialised in that they needed a small envelope size, must operate at low filament current and be non microphonic. Due to the National Health hearing aid being introduced in 1948, Mullard developed a series of 10mm subminiature valves to power it ......we have two of these smashing hearing aids available for sale elsewhere on the site - anyhow, I digress......... These 10mm specials  were swiftly superceded by the DF66, DL66 and DL68 which...