| Author |
Message |
Tim Williams
Guest
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 Posted:
Wed Jan 12, 2005 8:46 pm Post subject:
Re: Basic Question |
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"Ian Iveson" <IanIveson.home@blueyonder.co.uk> wrote in message
news:uJYEd.65895$C8.36306@fe3.news.blueyonder.co.uk...
| Quote: | If you regard the valve as a fixed voltage source with series output
resistance Rp, then maximum power output is when Rload = Rp. To get
2Rp you must be working with a different definition or assumption
somewhere.
|
Rp is a response, Thevenin need not apply. Remember that internal NFB thing
triodes have?
| Quote: | Holding constant 1V signal to grid, highest power was with load of
1.7k
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Indeed it is. Because you are testing for Thevenin. Congraduations,
Thevenin still works.
| Quote: | So what does "max power transfer" mean?
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Crank grid drive peak up to grid bias voltage. "Highest undistorted power
output" - distortion meaning leaving class A1.
| Quote: | lower than what, John? And why does lower follow from the fact that
it is a current source? Is it a more linear current source at low
Rload?
|
You get more power. (Linearity is a coincidental side effect.)
Ian, honestly -- when's the last time you got out a load line!?
| Quote: | I have wondered for ages...can't remember resolving the matter...why
the common loading for 4 * EL84 pp amp (for example) is 4k no matter
whether it is triode, UL or pentode mode. Exceptions are for class A
"hi-fi" which use 5k.
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Is it "class AB"? (In quotes because no such thing happens with a cathode
bias resistor.)
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
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Ian Iveson
Guest
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| Posted:
Wed Jan 12, 2005 9:22 pm Post subject:
Re: Basic Question |
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| Quote: | Rp is a response, Thevenin need not apply. Remember that internal
NFB thing
triodes have?
|
Let's not start the triode NFB mumbo jumbo again. Any non-linear
response is enough to make your point thanks. I made the same point,
Ra varies.
| Quote: | Holding constant 1V signal to grid, highest power was with load
of
1.7k
Indeed it is. Because you are testing for Thevenin.
Congraduations,
Thevenin still works.
|
Precisely my point. Don't need your congratulations thanks. Max
power is when Rload = Ra.
Now perhaps *you* could explain, in your own words, where the 2
comes from?
Whether max power is at Rload = Ra, or Rload = 2Ra, or whatever,
depends on what is meant by max power.
| Quote: | lower than what, John? And why does lower follow from the fact
that
it is a current source? Is it a more linear current source at
low
Rload?
You get more power. (Linearity is a coincidental side effect.)
|
Don't get any power at all with zero load do you, clever clogs.
But John is talking about more linear. You could guess this by
reading my response. See how I said "is it more linear". Could even
be a rhetorical question if you think about it.
| Quote: | So what does "max power transfer" mean?
Crank grid drive peak up to grid bias voltage. "Highest
undistorted power
output" - distortion meaning leaving class A1.
|
But as we have agreed, it could mean something else. Actually, I
think "max power output" would be a more straightforward way of
putting what you mean. Max transfer suggest efficiency to me, which
could be misleading.
| Quote: | Ian, honestly -- when's the last time you got out a load line!?
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What's a load line?
cheers, ian |
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Sander deWaal
Guest
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| Posted:
Wed Jan 12, 2005 11:42 pm Post subject:
Re: Basic Question about RL/Ra |
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Patrick Turner <info@turneraudio.com.au> said:
| Quote: | Now, anything with a hard cover, and about old fashioned electronics
and perhaps used as a textbook in 1950 is not to be seen in the local book
stores and methinks
that they are spirited off to markets willing to pay serious money, rather than
the $10 I was able to obtain them for.
|
If only that were true.
I dare not think about all the books that were/are trashed as
"obsolete".........
That's why I try to buy every pre-1970 book regarding electronics,
whether it is about TV, RF, measuring gear or audio.
One of the best books I ever bought was a book in Dutch called
"Precise Electronic Circuits" by some Philips engineers.
It dates from 1966 and every time I ask myself questions when fiddling
with vacuum, this book has an answer to them.
Sort of like the Dutch equivalent to RDH4.
Also, there are some Telefunken books on the physics of tubes, like
400 pages just about cathode materials and their behaviour.
Keepers for the day I'll finally understand it all :-)
--
Sander de Waal
" SOA of a KT88? Sufficient. " |
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Sander deWaal
Guest
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| Posted:
Wed Jan 12, 2005 11:46 pm Post subject:
Re: Basic Question about RL/Ra |
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Patrick Turner <info@turneraudio.com.au> said:
| Quote: | If only a fortune could be made from knowing something about tubes.........
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Will they say the same about Windows XP in 2050? ;-)
| Quote: | I should have been around in 1950.
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Dude, consider yourself lucky.
I was born in '66 , so I missed all the fun.........
| Quote: | But the competition was much more severe then....
|
Depends, I think.
Not all of us are called Walker or Keroes, but there would have been a
place for us.
| Quote: | Have a great year,
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Likewise.
--
Sander de Waal
" SOA of a KT88? Sufficient. " |
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Tim Williams
Guest
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| Posted:
Thu Jan 13, 2005 4:35 am Post subject:
Re: Basic Question |
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"Ian Iveson" <IanIveson.home@blueyonder.co.uk> wrote in message
news:Q8cFd.111260$48.95717@fe1.news.blueyonder.co.uk...
| Quote: | What's a load line?
|
Aside from all the things which I graciously snipped, this here says it all.
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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Stewart Pinkerton
Guest
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| Posted:
Thu Jan 13, 2005 7:29 am Post subject:
Re: Basic Question |
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On Wed, 12 Jan 2005 17:35:45 -0600, "Tim Williams"
<tmoranwms@charter.net> wrote:
| Quote: | "Ian Iveson" <IanIveson.home@blueyonder.co.uk> wrote in message
news:Q8cFd.111260$48.95717@fe1.news.blueyonder.co.uk...
What's a load line?
Aside from all the things which I graciously snipped, this here says it all.
|
Indeed it does. It says that he wants to learn. Would that this were
true of more of us........................
--
Stewart Pinkerton | Music is Art - Audio is Engineering |
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Patrick Turner
Guest
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| Posted:
Thu Jan 13, 2005 8:27 am Post subject:
Re: Basic Question |
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Ian Iveson wrote:
| Quote: | Rp is a response, Thevenin need not apply. Remember that internal
NFB thing
triodes have?
Let's not start the triode NFB mumbo jumbo again. Any non-linear
response is enough to make your point thanks. I made the same point,
Ra varies.
Holding constant 1V signal to grid, highest power was with load
of
1.7k
Indeed it is. Because you are testing for Thevenin.
Congraduations,
Thevenin still works.
Precisely my point. Don't need your congratulations thanks. Max
power is when Rload = Ra.
Now perhaps *you* could explain, in your own words, where the 2
comes from?
Whether max power is at Rload = Ra, or Rload = 2Ra, or whatever,
depends on what is meant by max power.
lower than what, John? And why does lower follow from the fact
that
it is a current source? Is it a more linear current source at
low
Rload?
You get more power. (Linearity is a coincidental side effect.)
Don't get any power at all with zero load do you, clever clogs.
But John is talking about more linear. You could guess this by
reading my response. See how I said "is it more linear". Could even
be a rhetorical question if you think about it.
So what does "max power transfer" mean?
Crank grid drive peak up to grid bias voltage. "Highest
undistorted power
output" - distortion meaning leaving class A1.
But as we have agreed, it could mean something else. Actually, I
think "max power output" would be a more straightforward way of
putting what you mean. Max transfer suggest efficiency to me, which
could be misleading.
Ian, honestly -- when's the last time you got out a load line!?
What's a load line?
cheers, ian
|
Maximum power isn't necessarily at 1Ra, 2Ra,3Ra etc.
But if you all go to
http://www.turneraudio.com.au/htmlwebpgs02/eh6550pographs.htm
and then look at the fourth graph from the top of the page for a single
SET
using a trioded 6550, you will see that the maximum PO of 9.5 watts
before grid current or cut off occur is at 3.5K
Idle conditions are at Ea = 450v and Ia = 80 mA, so Pdq = 36 watts.
If one has the triode set up at Ea = 300v and Ia = 120 mA,
then the peak unclipped power is at a lower RL.
Ra for a 6550 in triode is about 1,000 ohms.
To know what the best load match is for any given condition
means one has to examine and calculate, and not just make wild guesses
or
pronounce general rules when none can apply.
If one doesn't know about loadlines, then one knows SFA about tubecraft,
and one should remedy the knowledge shortfall imho.
Patrick Turner. |
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Sander deWaal
Guest
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| Posted:
Fri Jan 14, 2005 12:54 am Post subject:
Re: Basic Question |
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"Tim Williams" <tmoranwms@charter.net> said:
| Quote: | "Ian Iveson" <IanIveson.home@blueyonder.co.uk> wrote in message
news:Q8cFd.111260$48.95717@fe1.news.blueyonder.co.uk...
What's a load line?
Aside from all the things which I graciously snipped, this here says it all.
|
I understand Ian's comment as being said with tongue-in-cheek, but who
am I....
:-)
--
Sander de Waal
" SOA of a KT88? Sufficient. " |
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Jon Yaeger
Guest
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| Posted:
Fri Jan 14, 2005 12:58 am Post subject:
Re: Basic Question |
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in article hckdu09tfa52886n7kpvj5dkcukp3csob3@4ax.com, Sander deWaal at
nospam@wanadoo.nl wrote on 1/13/05 2:54 PM:
| Quote: | "Tim Williams" <tmoranwms@charter.net> said:
"Ian Iveson" <IanIveson.home@blueyonder.co.uk> wrote in message
news:Q8cFd.111260$48.95717@fe1.news.blueyonder.co.uk...
What's a load line?
Aside from all the things which I graciously snipped, this here says it all.
I understand Ian's comment as being said with tongue-in-cheek, but who
am I....
:-)
|
Well, according to Lord valve, you are . . . . . .
;-) |
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Sander deWaal
Guest
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| Posted:
Fri Jan 14, 2005 1:57 am Post subject:
Re: Basic Question |
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Jon Yaeger <jono_1@bellsouth.net> said:
| Quote: | What's a load line?
Aside from all the things which I graciously snipped, this here says it all.
I understand Ian's comment as being said with tongue-in-cheek, but who
am I....
:-)
Well, according to Lord valve, you are . . . . . .
;-)
|
Nuts? :-)
Which brings me to the following:
Adam Stouffer, if you're reading this, your nuts are on the way.
By pigeon :-)
--
Sander de Waal
" SOA of a KT88? Sufficient. " |
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Ruud Broens
Guest
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| Posted:
Fri Jan 14, 2005 11:41 pm Post subject:
Re: Basic Question |
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"Sander deWaal" <nospam@wanadoo.nl> wrote in message
news:u2odu01a6vmt7u417v90c02d29pp3rdni3@4ax.com...
:
: >Well, according to Lord valve, you are . . . . . .
:
: >;-)
:
: Nuts? :-)
:
: Which brings me to the following:
: Adam Stouffer, if you're reading this, your nuts are on the way.
:
: By pigeon :-)
:
: --
: Sander de Waal
: " SOA of a KT88? Sufficient. "
You mean: like in the Monty Python movie - coconuts-pigeon theory :-)) ?
Rudy |
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