[HBR] Anyone tried these tubes?

[Bill Higgs]

Hello,

As a relatively new member of the list, I am not aware if this has been
discussed earlier - if so, my apologies. After reading Joel Balogh's article
in July 1966 QST where he sings the praises of the 6EH7 and 6EJ7 frame-grid
pentodes, I have obtained several to play with in the front end of an
HBR-16. His focus seems to be noise figure and other factors rather than
cross modulation performance, but he places these little bottles in the same
ballpark as the legendary 7788. Balogh used the 6EH7 as the RF amp (remote
cutoff) and the 6EJ7 (sharp) as a mixer, claiming good results. One drawback
is that the tubes are run at about 15-20 ma cathode current, and with some
degenerative cathode feedback to cut the overall gain down a bit. Also not a
drop-in replacement; the tubes have 9-pin bases to accommodate a pin for the
internal shield (which may mean you can get away without an external shield
if the layout is well-spaced).

Looks like the 6EH7 might be worth trying as an IF amp, as that was its
original intent (for TV receivers). I believe either Swan or Drake may have
used it at one time in some of their IFs.

Anybody tried these tubes? BTW, Antique Electronic Supply has the 6EH7 on
sale at fifty cents (!) each if anyone wants to give it a try.

Bill Higgs, NT4C