Re: Boosted Triode


"flipper" <flipper@xxxxxxxx> wrote in message
news:2gas05p932mdsogp6jcb2ocig4q9tchbp9@xxxxxxxxxx
On Fri, 15 May 2009 11:22:02 +0100, "Ian Iveson"
<IanIveson.home@xxxxxxxxxxxxxxxx> wrote:


"flipper" <flipper@xxxxxxxx> wrote in message
news:6fnp0593tp8gkoub8cs33u4cq2jlissuh6@xxxxxxxxxx
On Fri, 15 May 2009 00:31:14 +0100, "Ian Iveson"
<IanIveson.home@xxxxxxxxxxxxxxxx> wrote:

flipper wrote:

<snip>

But why not simply increase the HT by 100V? I really
don't
see the point of all this jiggerypokery.

Because you'd red plate.

His example is a class A amplifier and you'd need
the
75mA
idle at the
higher B+. The plate can't handle it.

Good, thanks. That's my first question dealt with,
assuming
you are right about the anode's max power.

I see from this and your second post you're now off on
whether 75mA is
the 'actual max power'...

Off? Not me, I know power is measured in Watts.

You're off on whether 75mA at 400V are the 'right
numbers'
for the
blooming tube, as if it made any difference to
explaining
his circuit.

Off? Not me, I was correctly remarking on the actual
circuit
posted, not your concept of some general principle.

So you were asking why not increase B+ another 100V on a
circuit you
already consider to be red plating.

Clever.

Indeed. Now you see it...

It doesn't matter if his example using 75mA is
precisely the 'max power', the principle remains.

What principle? I can't see that you've introduced one,
so
how can it remain? Was it here before we arrived? Tell
me
what and where it is and I'll do my best to address it.

The principle of boosting the blooming triode mode to
get
more power
out of the thing.

If you mean that, as a general rule,

As a general technique. That *is* his point.

Who's point? How do you know? What point anyway? What are
you on about?

more power can be
extracted from a pentode or beam tetrode if the screen
voltage is increased,

It's being operated triode mode, not pentode or tetrode
mode.

Getting desperately silly now. It's still an example of a
pentode or beam tetrode. If you went to a shop and asked for
a triode, they would be quite correct in saying they didn't
have one for sale, if all they had in stock were 6L6.

than that seemed too obvious to be
worth discussing, but go ahead if that's what you want to
do.

If it was so 'obvious' to you then why were you asking
about
increasing B+?

To raise the issue. What's obvious to me is not necessarily
obvious to others. It was not immediately obvious that
raising the HT would result in a red anode, anyway, until I
went to look at, and post, 6L6 data. I could have looked at
the datasheet first, of course, but I'd rather raise the
issue. It all worked out quite nicely, allowing you display
your knowledge, which seems to be what you like to do. Is
this getting through to you yet? I'm getting a bit bored
now, and would rather talk about the circuit. I'm not keen
on discussing me. I'm a private and quite secretive kind of
chap when it comes to newsgroups.

Why some want to give it the name "boosted", as if it is
a different mode of operation, I really don't know.
Neither
can I see what "principle" is involved that is peculiar to
the posted circuit, which conforms to the usual operating
rules.

Because it's triode mode and not, as you suggest, the
'typical'
pentode operation where you simply stick a fixed V on the
screen.

Suggested what? Where?

Pentode operation often depends on *not* having a fixed V on
the screen, incidentally. There's another opportunity for
you to learn something. My amps modulate the screen in order
to operate in pentode mode, when I want them to, which isn't
very often because my knees are too far to the right and I
risk early screen and grid current, and the extra power
isn't worth having. That's why I was considering changing to
6L6, as I have been saying for some time.

To me, the real issues here are about the safe
operation of a particular valve, the details of a
particular
circuit, and the principle of what sounds best.

Fine. So I'll amend the answer to it's a lousy idea to
suggest
increasing B+ another 100V on a circuit you think is
already red
plate.

I was asking why not. That's not the same thing as
suggesting you do it.

I really don't know why you go off into these nonsensical
babbles when
you weren't going to build one anyway.

I can't be wrong and nonsensically babbling at the same
time, clot. There is a great deal of the world you can't
make sense of. Don't blame me, I'm trying to help you.

Valves are different. Those with knees further to the
right
will not be so amenable. Be wary of making a principle out
of it.

There ain't no blooming 'knee' when a triode.

So what? and there is, anyway, dafty. Look at the original
article's characteristic curves.

The chap needs
6550 perhaps. It's been a while since they've been
mentioned
AFAIR. Hooray for the 6550. Or KT88 mebs.

One can always propose getting a 'bigger tube' or, as
I
did, to use
two. The same principle would apply to those as well.

As did we both, but a bigger one would be better IMO.
But
there's that principle again, dammit.

Right. You could also boost the bigger tube or the pair
for even more
power.

So what?

Exactly what it says. The principle applies whether a 6L6,
a 'big
tube' or duals, or pairs, or quads, or...

So what?

On which side of the screen are you asking? The
'extra'
acceleration
from the 'extra' 100 volts between the grid and screen
or
the 'loss'
of acceleration from the 'extra' 100 volts going from
the
screen to
plate?

The question is perfectly clear as asked, and I can't
see
what your quibble is.

The 'quibble' is you only talk about 'one side' of the
screen. They
pick up 100V of acceleration on the cathode side and
lose
it again on
the other.

So why did you ask me which side I was talking about?

It was to give you a clue that what you 'wonder' about
being 'lost' is
also gained.

So you asked a question when you already knew the answer.
Isn't that what you are telling me is nonsensical babbling?

And
why have you switched from the "energy" in my question, to
"acceleration"?

What makes you think "100V" is energy?

I don't. I asked where the "100Vs-worth" of energy goes.
Since the electron-volt (eV, I think) is a unit of energy, I
hoped you would know what I meant. You replied in terms of
acceleration. I'm telling you that doesn't answer my
question about energy, sigh...

Acceleration is where the energy comes from.

Er...maybe, maybe not. Could be a very misleading statement,
and I can't see where it would be a useful one without
qualification. If you think about it, acceleration doesn't
come from, or go to, anywhere, does it? But energy must
always go somewhere, and come from somewhere, mustn't it?
That's why there is a principle (something you're fond of,
yes?) of conservation of energy, but not a principle (I'll
say it as often as I can if it pleases you) of conservation
of acceleration. There you are, more education for your
efforts. Keep 'em coming!


This was the question:

"Now what I'm wondering is where all that energy goes. The
electrons, to put it crudely, arrive at the anode having
lost 100Vs-worth of energy since they passed the screen.
What happens to it?"

Same place it goes in an audio amp when the screen is
fixed at 300V
and the anode swings to 200V, or to 100V, or to 50V. Or,
in other
words, the entire negative half of every sine wave.

But where does it go?

What you say about acceleration appears obvious to me, but
the question about lost energy rather less so, which is
why
I raised it.

Never bothered you before.

How would you know?

The energy gained/lost due to the electrostatic field
comes from the
electrostatic field.

Hmm...getting warm. Where does it go to?

Let's say the circuit was derived the other way
round,
and
the chap began with a triode with Va 500V, and he
proposed
his circuit as a way of reducing Va. What for? Would
it
be
more linear? Would the increase in HT efficiency be
more
than that lost by the extra supplies? How long would
be
payback time be, considering the cost of components
and
extra construction?

The problem with your question is the chap can't
begin
with it the
other way around. It would red plate.

I wasn't suggesting he did it for real...just for the
sake
of logical process.

Same for my reply. Whether the example physically
exists
or not the
logic has to fit reality to be of any use.

Whatever, sigh...

I don't know what's so confusing.

The purpose is to get more power out of the tube and it
doesn't add
anything to postulate running the tube at x times what
would burn it
up as an 'alternative'.

That doesn't require someone imagine you meant a 'real
chap' or a
'real tube', neither of which I did so there was no need
to 'explain'
it. You asked why not do X and I explained that X would
red plate.

Barking, truly. I made it clear from the start that I was
talking about this particular valve in this particular
circuit. You can ponder principles if you like, but don't
expect others to be constrained by your restricted thought
processes.

If you now want claim you were daft enough to propose
increasing B+ in
a circuit that you already considered to be red plate, not
to mention
one you had no intention of building, then so be it.

I never proposed it. I asked a question. As you have already
remarked, it was a clever question, amongst others.

But enough of my cleverness, what about the sound?

Ian


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