Mystery Tubes Revisited.
Fred Whitlock
some mystery Chinese driver tubes that accompanied a VAL VAA70 Mark III
amplifier. You may recall that this amp is based somewhat on the Dyna
Stereo 70 circuit and uses EL 34's on the output. The mystery driver tubes
have no marking at all on them and the data sheet that accompanies the amp
calls them 3F2, a non exitent tube type-at least in the West. Ned Carlson
was kind enough to rush me a pair of 6N2P and a pair of 6GH8. The 6N2P had
the same results as the 7199 and 6922-they lit but passed no signal. I
inserted the pair of NOS 6GH8's and, presto, I got sound. The amp didn't
sound as good (constrained and tight sounding) with the 6GH8's, though, as
it did with the mystery tubes so I assume they are close but not exactly
there.
So do the RAT readers have any more suggestions now knowing what doesn't and
what does (to a degree) work in the amp? I'd still like to nail this down
as closely as possible. Thanks for any suggestions. I see light at the
end of the tunnel. Thanks to all who sent suggestions. Good listening.
--
Fred
AudioNow!
http://www.audionow.com
Tim Reese
OvrReactor <ovrre...@aol.comnospam-> wrote:
>6AX8, 6BL8, 6EA8, 6GJ8, 6HL8, 6KD8, 6LM8, 6LN8, 6MQ8, 6MU8, and 6U8. There are
>alos some 4 digit industrial types that match this basing.
And 6678 ("special" 6U8) or 7687 (with "improved characteristics").
--
----------------------------------------------------------------------
Tim Reese, MGH NMR Center re...@nmr.MGH.harvard.edu
OvrReactor
has the same basing (9AE, check the GE essential characteristics book). Likely
candidates now are the following triode-pentode tubes;
6AX8, 6BL8, 6EA8, 6GJ8, 6HL8, 6KD8, 6LM8, 6LN8, 6MQ8, 6MU8, and 6U8. There are
alos some 4 digit industrial types that match this basing.
Head out to a hamfest and pick a bunch of these up, or give Ned a call and see
what he thinks. (I may have some 6EA8's in my "archives" that I could sell you
at a reasonable cost.)
Happy Hunting!
Tom Mitchell
email - OvrRe...@aol.com
Fred Whitlock
work in this circuit. Obviously someone is making something in China but,
apparently, the rest of us don't know anything about it. What surprises me
now is why the VAL people describe this amp as similar to the Dyna ST-70.
It seems to share nothing in common with it except for 4 EL4 output tubes
and three transformers. Good listening.
Fred
AudioNow!
http://www.audionow.com
Tim Reese wrote in message <73fo4b$b...@larmor.nmr.mgh.harvard.edu>...
>In article <19981124202901...@ng-fr1.aol.com>,
>OvrReactor <ovrre...@aol.comnospam-> wrote:
>>6AX8, 6BL8, 6EA8, 6GJ8, 6HL8, 6KD8, 6LM8, 6LN8, 6MQ8, 6MU8, and 6U8.
There are
>>alos some 4 digit industrial types that match this basing.
>
Fred Whitlock
ages. What I really want to get to is the current production tube this
thing probably is. I assume it's made in China since the amp it came with
is Chinese but I know of nothing from my sources that acts like a 6GH8. Did
say 6BH8? If I did my face is turning beet red. The tube that worked in
the amp was a 6GH8. Thanks for the response. Good listening.
Fred
OvrReactor wrote in message
<19981126223515...@ng-cc1.aol.com>...
>Did you try a 6U8? The triode section of the 6BH8 seems similar to a
6C4/12AU7
>triode, having a mu of 17. The triode in the 6U8 has a mu of 40. Maybe
this
>is the tube you need.
>
>I wish I could toss that sucker up on my workbench, I'm sure the solution
is
>simple. You REALLY should be using a scope to find out whassup.
>
>Regards,
>Tom Mitchell
OvrReactor
Dennis @Worldnet
The 6GH8 is actually the same tube as a 7199. The pins
are just connected differently. I would suggest finding
a 6GH8 of another make you like. Or you could change
the connections on the tube sockets so that 7199's
could be used instead.
Hope this is helpful,
Dennis
OPCOM
There were so many made, there ought to be plenty of NOS around.