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'...... ;-)

In message , Keith G
writes

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'...... ;-)



Excellent! So it's a pair of 845s and a couple of Sowter's finest SE
OPTs next then?
--
Chris Morriss

In message , Keith G
writes

[tales of joy]

C'mon then...how does it sound?

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

You don't sell your granny. Grannys are what you have a valve amp for.
You give her a pair of fat wires (one in each hand) and say 'listen to
this, grandma, it goes up to 11'.

16mm^2 distribution box tails work nicely (replace the fuse with a bit
while you're at it). None of that posh silver cable, she'll nick it.

--
Regards,
Glenn Booth

On Mon, 5 Jul 2004 21:50:25 +0100, Chris Morriss
wrote:

In message , Keith G
writes

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, I *told* you it needed a pi filter! :-)

Excellent! So it's a pair of 845s and a couple of Sowter's finest SE
OPTs next then?

Hmmmm, now *that* is a real project - you'll concentrate much more
closely with a 4-figure B+ rail!

--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
news
On Mon, 5 Jul 2004 21:50:25 +0100, Chris Morriss
wrote:

In message , Keith G
writes

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, I *told* you it needed a pi filter! :-)

Excellent! So it's a pair of 845s and a couple of Sowter's finest SE
OPTs next then?

Hmmmm, now *that* is a real project - you'll concentrate much more
closely with a 4-figure B+ rail!


Hmm, the first step on the road to valve escalation madness, see Audio
Bizzarro http://www.spiritone.com/~tube/constructor.htm plenty of 845 &
Sowters there. That Altec 816 cab would be perfect for my Cinerama home
theatre project though ;-)


Stewart Pinkerton | Music is Art - Audio is Engineering