[Milsurplus] BC-348's and 6AC7s...

[Kenneth G. Gordon]

The 6AC7 is a MUCH MUCH hotter tube than the 6SK7, and IFF it 
didn't oscillate, it SHOULD provide much lower noise, and considerably 
more sensitivity.

However, it is not a good idea to use the 6AC7 since it most often 
oscillates at VHF or even at frequencies in the tuning range of the BC-
348 unless you take particular care to make sure it is either neutralized 
or so well shielded, grid to plate, that it can't oscillate.

If it oscillates, and all things being equal, it WILL somewhere, then you 
get MORE noise and LESS sensitivity than the 6SK7s.

I wouldn't do it.

Ken W7EKB