[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

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