One old kink was to plug in 717A tube in the RF. I don’t know if this tube will work in both RF slots

though. 717A are quite uncommon now but used to be all over the place. I found the 6AC7 to be

bad news; sharp cutoff, not so good for strong signals. My feeling now is if you want to modify the

active devices, go all out and make plug in ss devices.  One thing that still is a BC-348 mystery to me

is how much the “shorted turn selectivity kink” actually improves selectivity. Also to change the last

IF winding to normal inductance and coupling and not overcoupled. I mean, quantify the result. It’s

on my project list but still way down there.

-Hue Miller