Well, after a week's heavy fettling (on and off) the triode amp is making
noises:

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

(I've written it up as 'tips for anyone considering it' as I get quite a bit
of post from people on the subject of valve amps and getting into it.)


The Good - Even in the very first few minutes of running this amp it's
obvious that the sound quality is/is going to be quite simply *stunning*.
The clarity gets you straight away, separation and imaging, tone etc. etc.
are all quite remarkable. Swim said it sounded 'accomplished'.....??

The Bad - It's humming like a good 'un and I suspect it's going to be a
bugger to sort....

The Ugly - Well, I think it's cute, but you'd never sell 'em looking like
this......

http://www.apah69.dsl.pipex.com/keit.../ampkit136.jpg

......would you??

:-)

Keith G wrote:
Well, after a week's heavy fettling (on and off) the triode amp is
making noises:


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

snip

The Bad - It's humming like a good 'un and I suspect it's going to be
a bugger to sort....

The Ugly - Well, I think it's cute, but you'd never sell 'em looking
like this......

http://www.apah69.dsl.pipex.com/keit.../ampkit136.jpg

.....would you??

:-)

I like it, whats the damage to buy one????????????????????????????????



--
Dave xxxx
http://www.davewhitter.pwp.blueyonder.co.uk/

Music is Art - Audio is Engineering
Steam is Fun

"Dave xxxx" wrote in message
...
Keith G wrote:
Well, after a week's heavy fettling (on and off) the triode amp is
making noises:



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

snip

The Bad - It's humming like a good 'un and I suspect it's going to be
a bugger to sort....

The Ugly - Well, I think it's cute, but you'd never sell 'em looking
like this......

http://www.apah69.dsl.pipex.com/keit.../ampkit136.jpg

.....would you??

:-)

I like it,


Ok, strangely enough so does Shiny Nigel (and me), so you are not
alone........!! :-)


whats the damage to buy one????????????????????????????????


Say £500 worth of parts (comfortably) and a week of my time, so that would
be about £525 in total, but (as it is atm) it would hum loud enough to
silence a washing machine...... ;-)

Phil http://www.bluebellaudio.com/ says one of these ponced up with a fancy
chassis would/will cost anyone about £3,000. How much he would charge for
one made up in a similar 'lab style' (unpainted grey chassis, exposed
trannies, screw heads, bloodstains everywhere....), I don't know - give him
a call.

I gotta say it, present hum notwithstanding, the sound really is
*stunning* - and that's from a confirmed/committed valvie who's no stranger
to the Wonderful Sound Of Valvey Things (and whose current valve amps are
not ****e)......!!!

(Phil's just about to put a couple of 300B triode amps on eBay apparently!)

On Sun, 4 Jul 2004 15:46:17 +0100, "Keith G"
wrote:


"Dave xxxx" wrote in message
...
Keith G wrote:
Well, after a week's heavy fettling (on and off) the triode amp is
making noises:



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

snip

The Bad - It's humming like a good 'un and I suspect it's going to be
a bugger to sort....

The Ugly - Well, I think it's cute, but you'd never sell 'em looking
like this......

http://www.apah69.dsl.pipex.com/keit.../ampkit136.jpg

.....would you??

:-)

I like it,


Ok, strangely enough so does Shiny Nigel (and me), so you are not
alone........!! :-)


whats the damage to buy one????????????????????????????????


Say £500 worth of parts (comfortably) and a week of my time, so that would
be about £525 in total, but (as it is atm) it would hum loud enough to
silence a washing machine...... ;-)

Phil http://www.bluebellaudio.com/ says one of these ponced up with a fancy
chassis would/will cost anyone about £3,000. How much he would charge for
one made up in a similar 'lab style' (unpainted grey chassis, exposed
trannies, screw heads, bloodstains everywhere....), I don't know - give him
a call.

I gotta say it, present hum notwithstanding, the sound really is
*stunning* - and that's from a confirmed/committed valvie who's no stranger
to the Wonderful Sound Of Valvey Things (and whose current valve amps are
not ****e)......!!!

(Phil's just about to put a couple of 300B triode amps on eBay apparently!)




Keith - where's the MP3 of the hum? Maybe we can speed up the
tracking-down process.

d
Pearce Consulting
http://www.pearce.uk.com

In message , Keith G
writes

"Dave xxxx" wrote in message
...
Keith G wrote:
Well, after a week's heavy fettling (on and off) the triode amp is
making noises:



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

snip

The Bad - It's humming like a good 'un and I suspect it's going to be
a bugger to sort....

The Ugly - Well, I think it's cute, but you'd never sell 'em looking
like this......

http://www.apah69.dsl.pipex.com/keit.../ampkit136.jpg

.....would you??

:-)

I like it,


Ok, strangely enough so does Shiny Nigel (and me), so you are not
alone........!! :-)


whats the damage to buy one????????????????????????????????


Say £500 worth of parts (comfortably) and a week of my time, so that would
be about £525 in total, but (as it is atm) it would hum loud enough to
silence a washing machine...... ;-)

Phil http://www.bluebellaudio.com/ says one of these ponced up with a fancy
chassis would/will cost anyone about £3,000. How much he would charge for
one made up in a similar 'lab style' (unpainted grey chassis, exposed
trannies, screw heads, bloodstains everywhere....), I don't know - give him
a call.

I gotta say it, present hum notwithstanding, the sound really is
*stunning* - and that's from a confirmed/committed valvie who's no stranger
to the Wonderful Sound Of Valvey Things (and whose current valve amps are
not ****e)......!!!

(Phil's just about to put a couple of 300B triode amps on eBay apparently!)





Do you think the hum is coming from the directly-heated filaments of the
300Bs, or from the HT line? (Heater hum is likely to be 50Hz, HT hum is
more likely to be 100Hz)

If it's the filament, then you could try using a resistive centre-tap on
the winding and earthing the CT, (or taking it to the bias circuitry or
whatever).

You may have a CT filament winding already of course....


--
Chris Morriss

I don't know if you ever work when you're tired, but if you do you can make odd
mistakes. I shouldn't do it but I did this weekend - put a 220k cathode
resistor in place of a 220 ohm. Wondered why it measured funny for a while!
(eventually sorted - got some 7951s going in place of 6L6s, bags more detail)
Sometimes you have to just go over the dumb ordinary bits until you notice
something you overlooked.

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

"Don Pearce" wrote


Keith - where's the MP3 of the hum? Maybe we can speed up the
tracking-down process.


OK, here's a clip from the record I've got on atm - Branford Marsalis
'Scenes In The City':

http://www.apah69.dsl.pipex.com/keith_g/show/hum002.mp3 2.5 Mb/1:49

The hum is before, during and after this 'end of track/beginning of next
track' snatch of music - which is to give you a sound level reference.

Recorded with an open mic, so it's a bit 'boggy' - no 'Line Out' luxuries
here, I'm afraid!! :-)

(Recording's another thing I've got no clue about! - Also not me best
speakers....!! ;-)

On Sun, 4 Jul 2004 16:58:57 +0100, "Keith G"
wrote:


"Don Pearce" wrote


Keith - where's the MP3 of the hum? Maybe we can speed up the
tracking-down process.


OK, here's a clip from the record I've got on atm - Branford Marsalis
'Scenes In The City':

http://www.apah69.dsl.pipex.com/keith_g/show/hum002.mp3 2.5 Mb/1:49

The hum is before, during and after this 'end of track/beginning of next
track' snatch of music - which is to give you a sound level reference.

Recorded with an open mic, so it's a bit 'boggy' - no 'Line Out' luxuries
here, I'm afraid!! :-)

(Recording's another thing I've got no clue about! - Also not me best
speakers....!! ;-)





Mmmmm... that hum is 100Hz, not 50, so it pretty certainly comes from
the power supply rails, not stuff like ground loops. Do you have a
spare fat electrolytic you could hang across power supply in parallel
with the one already there? See if that kills, or at least reduces,
the level.

d
Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote



Mmmmm... that hum is 100Hz, not 50, so it pretty certainly comes from
the power supply rails, not stuff like ground loops. Do you have a
spare fat electrolytic you could hang across power supply in parallel
with the one already there? See if that kills, or at least reduces,
the level.


OK, that's interesting and would be good if I *don't* have any ground loops.
No I ain't got any spare electrolytics, but I can damn soon rectify*** that!
(I actually managed to use up all the components - I've come a long way from
me motorcycle-fettling days when I always ended up with a jamjar full of
'leftovers' for each bike..... :-)

Interesting thing is that, now that I've got it on the computer, I 'scoped
it**:

http://www.apah69.dsl.pipex.com/keith_g/show/humpic.jpg

The different traces swap places exactly when I switch the leads over, so
summat's up. (Buggered if I know what tho' - I'm not much cop at scopes
either!)

Which reminds me I haven't had an answer yet to an earlier question - that
top trace will slowly slide down the screen over a period of time. Anybody
got any idea what causes that?


**You sods are turning me into a bloody techie!!

***techie pun?

:-)

"Chris Morriss" wrote


Do you think the hum is coming from the directly-heated filaments of the
300Bs, or from the HT line? (Heater hum is likely to be 50Hz, HT hum is
more likely to be 100Hz)


It's looking like the hum is 100Hz, but my scope telling me that it's
left-channel weighted. (If the scope can be trusted.....???)


If it's the filament, then you could try using a resistive centre-tap on
the winding and earthing the CT, (or taking it to the bias circuitry or
whatever).

You may have a CT filament winding already of course....


The filaments have their own transformers where the CT (if it is one - grey
and blue secondaries twisted togetther??) is taken up to a 200V rail which
it shares with the cathode resistors and bypass capacitor as in:

http://www.apah69.dsl.pipex.com/keit.../ampkit124.jpg

The red and yellow secondaries supply 2.5V @ 3A directly to the filament
(measured about 2.69V, IIRC)