6146A,B,W, 6HS6 vs 6AU6.

[Stewart Lyon]

After all the controversy over which type of 6146 to use, some
contributed by me, I'll bet it would take some pretty sensitve lab
equipment to measure any differance between the types in a given rig --
in either linearity or power out.  And certainly wouldn't make any
differance on the S-meter on the other end.  I think it's most important
to use the same type from the same manufacturer and if possible, the same
date code.  As k4jpn stated, the final should be neutralized by the
method that removes the plate and screen voltage.

As to the 6HS6 >< 6AU6 discussion, definitely use the the 6HS6 in at
least the in RF amp.  The SB-101 has a sensitivity of 1 uV and the
SB-102/HW-101 -- 0.35 uV .  This increased sensitivity comes entire from
the 6HS6s. I developed a Pentode Comparison Chart that was based on a Feb
'66 QST article ( and which I wish I could figure out a way to post).
This chart shows that the 6HS6 is about FIVE times a better tube for the
RF amp than the 6AU6 when gain and noise resistance are taken into
account.  This same chart shows that the 6GM6 is 3 times better than the
6BZ6 in the front end of the SB-300/1 (doesn't do a thing for the -303).

73, Stu -- W6CUX

BTW -- My company is switching servers so any mail sent to my slyon@
(varies) address may bounce.  Use the above JUNO address. Thanks.

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