A quick thank you to *everyone* who volunteered suggestions to cure the hum
problem on triode amp project. None of them were without merit, but the
problem was being caused by no more than the B+ being lifted from the wrong
side of the choke (itself a component of the circuit's 'pi filter') due to
some wattock reading the circuit wrong!! (Which is a bit of a mystery in
itself, because I'm the only one who's had a hand in actually building it
!!!??? :-)

Anyway, once the wires had been re-routed the hum disappeared completely -
absolutely silent!

See:

http://www.apah69.dsl.pipex.com/keit.../ampkit138.jpg


Now that the wire have been stuffed back in, there's only the 'normal'
amount of tiny hum audible less than 6 inches from the speaker grille. It's
a trade-off - no hum at all and swags of wire swinging in the breeze, or
tidy it up nicely and induce a tiny bit of (normal) hum!!! (Bit of scope for
some future tweaking here....)

The whole grisly tale can be seen on....

http://www.apah69.dsl.pipex.com/keit...de_project.htm

....if anyone's interested.

(Next up the 'Phono Stage To Sell Your Granny For'...... ;-)