6K7 sub for EF86

[vetmed]

At that online auction site I came across an adaptor that allows you to use 6K7 in place of EF86. The 6K7 is an octal based pentode with g1 taken to a top connector. I have no idea how to determine if this tube is a suitable replacement, but it sure looks cool! Also very intriguing is that the 6k7 is very cheap compared to NOS EF86 making it very attractive, and is available in many well known brands. If this is a viable sub I'd sure like to know.
       Robert Lees

[Paul Joppa]

6K7 is a variable-gain tube (i.e. nonlinear as heck) and has much less gain at Eros operating current than the EF86. Also, it's a metal tube (rings like a bell!) unless you get the -GT version. Totally not suitable.