[Tony Pike]

I have an amp that has etched for use 6U10, but in the tube sockets
are 6AC10. Is there a wide variance in these tubes? They are very
similar in performance, but are they interchangeable? It was replaced
when KT-90's were used instead of original KT88's. These tubes are hard
to source, I am also in search of 6LU8's. I reside in Calgary, Ab. and
the Parts Connexion does not supply them. Any advice would be soundly
appreciated...
Regards,
Tony.

[Peter Wieck]

Tony Pike wrote:
I have an amp that has etched for use 6U10, but in the tube sockets
are 6AC10. Is there a wide variance in these tubes? They are very
similar in performance, but are they interchangeable? It was replaced
when KT-90's were used instead of original KT88's. These tubes are hard
to source, I am also in search of 6LU8's. I reside in Calgary, Ab. and
the Parts Connexion does not supply them. Any advice would be soundly
appreciated...
Regards,
Tony.

The 6AC10 is listed as a direct substitution for the 6U10 and should be
just fine. It is three triodes in a single package (listed as "High Mu
triple-triode"). Other direct substitutions include the 6AV11 and the
6D10. NOTE: There is just enough variation between these tubes that in
some few circuits there may be gain differences. As this is a power amp
and you are doing no small-signal processing (microphone or phone
inputs, for example) you should be fine with any of the above. Just try
to use the same type in each channel.

The 6LU8 is a Pentode/Triode and not even nearly equivalent.

In general, I suggest that individuals who are given the dubious
distinction of being responsible for the care and feeding of tube
equipment should keep a good substitution-book or tube handbook handy
at all times.

http://www.amazon.com/Tube-Substitut.../dp/0672217465

And http://www.pmillett.com/technical_books_online.htm

Will point you to all sorts of resources and literature. But in all
seriousness, the Sam's book can be a life-saver, get one (of course, if
everyone does try, the price will be more than $2.49....)

Peter Wieck
Wyncote, PA