[Eeyore]

Phread wrote:

"Sander deWaal" wrote in message
Eeyore said:

A cathode needs to be hot for emission to take place.

Yep.

Whether it's heated directly or indirectly is moot for a preamp stage.

Nope.

A cathode tube, indirectly heated, has the same DC potential all over
its surface.
A DH cathode has a DC potential difference between both ends,
affecting the linearity and emission of electrons over the surface.

That's why they painstakingly winded the cathode several times up and
down along the grid and anode surface in an AD1, for instance.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

That's the kind of thing I had in mind when I said, "actually knows
absolutely nothing about, liked DHT's." Fools seem to think that
knowledge they don't posess does not exist, or is wrong. A truly
knowledgable person lives in awe at how much he doesn't know.

Yet many ppl live in awe of their own navels, esp toob freaks.

Graham

[Eeyore]

robert casey wrote:

Arny Krueger wrote:
"Eeyore" wrote in

I love it when clowns resort to 'voodoo science' !

A cathode needs to be hot for emission to take place.


Whether it's heated directly or indirectly is moot for a
preamp stage.


Not totally.

You have to remember that there is a significant voltage drop across a
filament. If the filament is inside a cathode tube (indirectly-heated
cathode), then this is moot. If the filament *is* the element of the tube
that actually emits the electrons (acts as the cathode), then the voltage
drop across the filament can possibly change the biasing situation within
the tube.

Some DHT tubes are designed to take this into account. Small tubes for
battery portable radios were designed like this. The tube data sheets
specify which end of the filament is to be more positive than the other.
The control grid must be built unevenly across the length of the filament.

That makes sense.

The 'curves' would effectively be a 'compound' of several ( in theory an
infinite number ) - think integration.

They're still triodes though and as such behave according to the triode
equation.

Graham

[Patrick Turner]

Andy Evans wrote:

Arny Krueger wrote:
In the real world the sound quality of an amplfiier can be characterized by
its frequency response and its amplitude response. It seems like there may
be some possibility that an amplifier based on a DHT could be a little less
linear than one based on an IDHT, because of the fact that different parts
of the cathode might be at different potentials. This means that the
biasing of the tube is not absolutely constant across the length of its
active elements. However, I strongly suspect that is never the case, no
matter which of he two ways the cathode is heated. This would show up in
the plate curves for the respective tubes.

As you say, there are quite a few factors that may contribute to the
difference in sound of DHTs, and I bow to others who know more about
construction - I just use them. There are so many factors that could
come into the equation, down to quality of construction, internal
architecture, quality of metals and coatings etc etc. While soundwise I
notice a family resemblence with small DHT tubes (which is what I work
with most), the globes generally seem to be a little smoother and more
detailed, and in the 1G4GT, for instance, the flat plates sound
different from the round plates (as happens with 6SN7s and 6J5Gs, viz
difference between CV1932 and CV1067). What contributes to what it's
hard to say. Doesn't stop one developing a rough ranking order of
favourites though. DHTs aren't universally better than IDHTs - I love
the 2C22, and it's better than, say, the 3B7 to my ears. But there's
something about the timbre of the best DHT small tubes (particularly in
the treble) that's quite addictive, and at times a bit awesome even.
Andy

Perhaps if you measured an average DHT you may find it to be more linear
than IDHT.
They did try to make triodes as linear as possible to avoid the gain
loss
and extra parts needed for anything with NFB.
Having the anode surface at a constant distance from a centralised
cathode probably is more linear than having a box section
with central anode, but the box section was probably easier to make,
and easier to be gripped by tube making jigs, so the girls with good
eyesight
didn't get cranky about having to make the darn things.
Their daughters were making tubes in 1960, and the best sighted girls
were employed on the 6AN7s, and frame grid 6EJ7 etc, and when
their sight deteriorated they were moved to KT88, but a nearly blind old
hag
could make a 300B.

Of course, by 1980, some basturd had stolen the heater out of triodes
and wrapped it up in plastic after it was assembled by very small girls
with extremely
good eyesight, and they called the non heated triode a Jayfet, after
Jay,
a gal who was first to succeed at assembling one in two minutes in
Japan.
She found there was no room for low clunky size Ra, so she inserted
thin slim high Ra, and also because she had pentode envy.
Being so small, there was also no room for the NFB fitted into real old
fashioned triodes.

Jay is still makin fets, but she's getting old now, and Toshiba will
pension her off soon,
unless they can cajole her into making diodes with an especially large
box of chocolates.
This is all because the fets she makes are not all that well matched.

Patrick Turner.

[Sander deWaal]

Patrick Turner said:


Perhaps if you measured an average DHT you may find it to be more linear
than IDHT.
They did try to make triodes as linear as possible to avoid the gain
loss
and extra parts needed for anything with NFB.
Having the anode surface at a constant distance from a centralised
cathode probably is more linear than having a box section
with central anode, but the box section was probably easier to make,
and easier to be gripped by tube making jigs, so the girls with good
eyesight
didn't get cranky about having to make the darn things.
Their daughters were making tubes in 1960, and the best sighted girls
were employed on the 6AN7s, and frame grid 6EJ7 etc, and when
their sight deteriorated they were moved to KT88, but a nearly blind old
hag
could make a 300B.

Of course, by 1980, some basturd had stolen the heater out of triodes
and wrapped it up in plastic after it was assembled by very small girls
with extremely
good eyesight, and they called the non heated triode a Jayfet, after
Jay,
a gal who was first to succeed at assembling one in two minutes in
Japan.
She found there was no room for low clunky size Ra, so she inserted
thin slim high Ra, and also because she had pentode envy.
Being so small, there was also no room for the NFB fitted into real old
fashioned triodes.

Jay is still makin fets, but she's getting old now, and Toshiba will
pension her off soon,
unless they can cajole her into making diodes with an especially large
box of chocolates.
This is all because the fets she makes are not all that well matched.



LOL!

And the first attemps by her to make a MOSFET were actually MISFITs,
I'd guess?

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Sander deWaal]

"Bret Ludwig" said:


snips

That's it. Of course, most Brit tubes like the KT series take the
Internatonal Octal base, but the "British Octal" was a short lived deal
that lived just long enough to get designed into some critical
military gear.


That's right.
Mazda SP61 = VT65 is an example.

Then there is the 9-pin EF50, the tube that won the war, according to
those who are into radar history.


Loctal tubes were a US product but there were Japanese high end
products in the modern era that used them. And often loctal variants of
popular audio types were very cheap on the surplus market-some still
are- and the DIY builder may still use them.


Uh?
Loctals were a Philips invention.
After the "red" series with Elephant feet (P-socket), they came out
with the "20" series, like ECH21, EBL21, EF22 and such.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Eeyore]

Sander deWaal wrote:

"Bret Ludwig" said:

snips

That's it. Of course, most Brit tubes like the KT series take the
Internatonal Octal base, but the "British Octal" was a short lived deal
that lived just long enough to get designed into some critical
military gear.

That's right.
Mazda SP61 = VT65 is an example.

Then there is the 9-pin EF50, the tube that won the war, according to
those who are into radar history.

Yes indeed.

The story about how it ended up on those bases is an interesting one too.

Graham

[Sander deWaal]

Here in Ohio said:


That's right.
Mazda SP61 = VT65 is an example.

Then there is the 9-pin EF50, the tube that won the war, according to
those who are into radar history.

Yes indeed.

The story about how it ended up on those bases is an interesting one too.

Graham

You're trying to use up all my spare time! I started looking for info
on the EF50, then went on from there.

A stop along the way is:

http://www.r-type.org/static/valvecpu.htm



Nice stuff!

BTW SP61 eq. should be VR65, typo.
Lots of them in war-surplus Gee units (still have one in the attic!)
In the late '40s, European amateurs used to build TV units with these,
revolving around a VCR517 CRT

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Andy Evans]

http://www.radiomuseum.org/dsp_searchtubes.cfm

http://www.r-type.org/static/museum.htm

Two good sites

[Phread]

"Here in Ohio" wrote in message ...
On Tue, 21 Nov 2006 14:52:14 -0800, "Phread"
wrote:


"Sander deWaal" wrote in message ...
Eeyore said:


A cathode needs to be hot for emission to take place.


Yep.


Whether it's heated directly or indirectly is moot for a preamp stage.


Nope.

A cathode tube, indirectly heated, has the same DC potential all over
its surface.
A DH cathode has a DC potential difference between both ends,
affecting the linearity and emission of electrons over the surface.

That's why they painstakingly winded the cathode several times up and
down along the grid and anode surface in an AD1, for instance.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

That's the kind of thing I had in mind when I said, "actually knows
absolutely nothing about, liked DHT's." Fools seem to think that
knowledge they don't posess does not exist, or is wrong. A truly
knowledgable person lives in awe at how much he doesn't know.


I think you missed out on this being an area where DHTs suck when
compared to more modern designs.

Only among those who've never heard a good DHT amp connected
to appropriate speakers... Apparently, that includes you.

Fred

[Sander deWaal]

"Phread" said:


I think you missed out on this being an area where DHTs suck when
compared to more modern designs.


Only among those who've never heard a good DHT amp connected
to appropriate speakers... Apparently, that includes you.



While I'm always ranting on about my hybrids and KT88 trioded in PP, I
always fall back on my little 2A3PP amp for a reference.

I still am puzzled by how good it sounds, and why I can't get that
sweetness back in any other amp I build.


--
- Ever seen someone with 5.1 ears? So, what does that tell you? -

[Bob Weiss]

Sander deWaal wrote:

Uh?
Loctals were a Philips invention.
After the "red" series with Elephant feet (P-socket), they came out
with the "20" series, like ECH21, EBL21, EF22 and such.

Loctals (tradename spelling "LOKTAL") were a US invention, by Sylvania.
Originally intended for automobile radio service.

Of course, what remained of Sylvania eventually ended up under the
control of Philips, so maybe you are technically right after all..

Bob Weiss N2IXK

[Patrick Turner]

Sander deWaal wrote:

Patrick Turner said:

Perhaps if you measured an average DHT you may find it to be more linear
than IDHT.
They did try to make triodes as linear as possible to avoid the gain
loss
and extra parts needed for anything with NFB.
Having the anode surface at a constant distance from a centralised
cathode probably is more linear than having a box section
with central anode, but the box section was probably easier to make,
and easier to be gripped by tube making jigs, so the girls with good
eyesight
didn't get cranky about having to make the darn things.
Their daughters were making tubes in 1960, and the best sighted girls
were employed on the 6AN7s, and frame grid 6EJ7 etc, and when
their sight deteriorated they were moved to KT88, but a nearly blind old
hag
could make a 300B.

Of course, by 1980, some basturd had stolen the heater out of triodes
and wrapped it up in plastic after it was assembled by very small girls
with extremely
good eyesight, and they called the non heated triode a Jayfet, after
Jay,
a gal who was first to succeed at assembling one in two minutes in
Japan.
She found there was no room for low clunky size Ra, so she inserted
thin slim high Ra, and also because she had pentode envy.
Being so small, there was also no room for the NFB fitted into real old
fashioned triodes.

Jay is still makin fets, but she's getting old now, and Toshiba will
pension her off soon,
unless they can cajole her into making diodes with an especially large
box of chocolates.
This is all because the fets she makes are not all that well matched.

LOL!

And the first attemps by her to make a MOSFET were actually MISFITs,
I'd guess?

Ah no, the Mosfet was made by the Turkish moslem girls
who emigrated in thousands to Germany.....
But yeah, its co-incidental that they are "misfits" of course.
Show them a bible and they chuck a fit.....

Unsigned, just in case Osama finds out who posted this crap.


--
"Due knot trussed yore spell chequer two fined awl miss steaks."