Hi Jim-
Your preamp was built around the 6H30P tube which is a souped-up,
and allegedly improved, substitute for the much more frequenly used
6922 tube family. The Telefunken tubes you have are likely NOS 6922
tubes. They could be genuine Telefunken tubes with the glass diamond
raised on the bottom of the tube between the pins, or they could be a
rebranded tube, or even a copy (not likely if they came from an honest
seller). Those tubes are of the more expensive preamp tubes, and some
of the best in that tube family as far as NOS tubes go. How they will
work in your amp and your system is entirely unknown to me. They
have been excellent in the applications I've heard them in. I sold some
of my German 6922's to a fellow A'goner who is local to me, who wanted
to do the same as you seem to. He was replacing the stock tubes in his
BAT preamp (sorry, I cannot recall which one, I think it was a VK-3i, but I
do recall he said they
were Sovtek tubes which is likely what you have in yours if it is stock). I
sold him some really nice NOS german tubes, and some british Mullards
as well. I heard back from him that the improvement he heard was
significant. As far as what you need to know about replacing them in
your preamp; it is really quite simple. Essentially they are plug-and-
play. You should power the system down, unplug the preamp from the
wall and let the tubes cool down a bit. Handle the tubes with clean
hands. A preamp does not require any special biasing procedures. To
remove the tube grasp it up at the top and gently rock it back and forth.
It will eventually come loose and allow you to pull up while rocking it.
With your vision impairment you may need some help from someone
alligning the pins of the tubes in order to put them in. They have nine
pins at the base with a gap in the circle of pins. The gap alligns with the
female socket to guide the nine pins into their proper slots. Once
alligned you should be able to gently push the tube down into the
socket. Do this for all the tubes you are replacing (I think there are eight
6922 type tubes and two 5881 - Replace with the appropriate tube type
- I'd guess the Telefunkens you have are all 6922's...5881's are not
many in current production, but I believe they are the same as the
6L6GC family of tubes - check with other BAT owners before making
that substitution). Make sure to put
the same tube type/brand/vintage into each of the sockets. I'm
sure if the person sold you an extra pair of tubes they are likely pretty
closely matched so you shouldn't need to worry there either. Once the
tubes are replaced, plug everything back in, power it all up and enjoy.
Tubes usually take about 30 minutes of warm-up time to sound their
best, while some tubes do take longer. Brand new tubes can take some
extra time to settle in. That's it for your preamp. Perhaps someone with
the same preamp can advise you further. Preamp tubes may last
anywhere from one to eight years depending upon the preamp, the tube,
and how long you listen. You will likely start to hear some weird noises
and some significant distortions when they get really bad. I think the
6922 has a rated lifespan of about 10,000 hours. Not sure about the
5881's.
Marco
