Gotta 866-866a- or 966 tube?


New Member
Jan 18, 2024
Helloo. Seems to be some Worldwide confusion on this tube.
Some say they are same. Not really. Per Tube Lore a 966 is an
866,a. Some say an 866 is an 866a.. but not Tube Lore. Later tubes
re even marked with both 866/866a numbers not really correct.
Which would make an 866a a 966 which it is not. The 966 is largely
omitted as not that popular. Having watched 2 NOS 866a fog
sorta fry and throw off lots a black bits inside in a 966 slot I can
confirm it simply is not the same...nor compatible. Can anyone
shed light on this obscure mystery. Thanks!

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing