Output classes A and AB
 

In article ,
Eeyore wrote:

Patrick Turner wrote:

One cannot have distortion cancelling by one tube cancelling that in
another when one is cut off.

THANK YOU !

Basics do matter.

Indeed they do, but neither Patrick, myself, or anyone else is correct
on every issue. In this case Patrick has vigorously asserted that this
view, which he holds in common with you, is true, but he has failed to
even attempt an argument that might demonstrate its truth. Patrick is
an extremely skilled and talented fellow in the practical aspects of
tube amp design and construction, but he has a very limited
understanding of what is going on behind the scenes in the theory of
tube amp operation.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Output classes A and AB
 

On Oct 26, 7:09 am, Eeyore
wrote:
Andre Jute wrote:
Eeyore wrote:
John Byrns wrote:
Patrick Turner wrote:

Cancelation of even order harmonics occurs in amps working in class AB
during that part of the wave forms which are in class A, ie, the bits
either side of the zero crossing.

But once each tube moves into cut off, nothing is cancelled.

Patrick, I'm surprised to hear you say this. What are you trying to
tell us, that the even order harmonics are only cancelled during those
parts of the cycle when both tubes are conducting, but that the even
order distortion components reappear during those parts of the cycle
when only one tube is conducting? If you actually believe that you
should go back to the books and study the theory of harmonic distortion
more carefully. I hope you didn't get this notion from the RDH4, I
haven't read the RDH4's harmonic distortion explanation, but if this is
what it says I have just lost any respect I had for the book. In a
perfectly balanced PP amplifier the even order harmonic distortion is
completely cancelled even when the tubes are cut off for parts of the
cycle.

I'd love to know how that happens. There's no cancellation of ANYTHING once one
side has ceased conducting !

Graham

Holy ****! Did I say yet that Poopie is ignorant and incompetent?

Nah, nobody can be that stupid and uninformed about tube basics.

Poopie must be cracking a joke. For the first time in his life.

Good on yer, cobber! If you can't be smart and informed, at least you
can try to be a clown, give people a giggle.

As an alleged 'wordsmith' you of all people ought to understand what cancellation
means. Apparently it went right over your head though.

Only to be expected from an ignorant non-technical ****wit.

Graham

Yeah, Poopie, you're the man when it comes to cancellations: your
definition of Class A, okay until then, cancelled out when you added
the superfluous words "under any signal condition".

Unsigned out of contempt

Output classes A and AB
 

On Oct 26, 7:21 am, Eeyore
wrote:
Andre Jute wrote:
Poopie Stevenson aka Eeyore wrote:
Andre Jute wrote:
Eeyore wrote:
Andre Jute wrote:

All of that follows logically from Poopie's absurd redefinition of Class A as
a Class in which "the output device(s)never cease conducting *under
any signal condition*," (emphasis added). It's ludicrous.

It's actually the only accurate definition.

I've already demonstrated several times that your words "under
any signal condition" make your definition grossly inaccurate.

But you're an ignorant **** and what you say is a load of ********.

Even when I'm right?

You're NOT right. Your ignorance is simply confusing you.

HOWEVER, to keep you happy I am happy to modify to modify my definition for clarity. I
already posted this once but I suppose you like to argue more than anything.

"the output device(s)never cease conducting *under any signal condition* within the rated
specification".

To be honest, to have to explicitly state "within the rated specification" is really a
case of pandering to fools, which certainly describes YOU, Jootikins.

Graham

Make up your mind, Poopie. Either Class A operation is possible only
with limited signal or it is possible, as you erroneously claim,
"under any signal condition". One or the other, not both.

There are about 500 messages across two threads in which you shilly-
shally about this gross error you, Pearce and Krueger have made. Which
is it?

Andre Jute
....who knows his own mind

Output classes A and AB
 

On Oct 26, 9:36 am, Eeyore
wrote:
John Byrns wrote:
Eeyore wrote:
John Byrns wrote:
(Don Pearce) wrote:
Eeyore wrote:

I'd love to know how that happens. There's no cancellation of ANYTHING
once one side has ceased conducting !

Because if you add an even harmonic to a signal, you have to make it
asymmetrical. You always get a peak coinciding with a trough on one
half cycle, followed by a peak coinciding with a peak on the next. If
you modify the signal to remove any asymmetry, you must by definition
remove the even harmonics.

Finally a man who understands the theory!

But it's not by ** CANCELLATION ** in the case of AB operation beyond the
crossover point. That's my issue with the description.

It does have that effect but the use of the word *cancellation* is wong IMHO.
There should be another way to describe it.

Cancelation is the right word,

********.

the two tubes, even when they, "operate beyond the crossover point",

When one tube has ceased conducting, there's NOTHING TO CANCEL, you IGNORANT
****WITTED ****.

CANCELLATION IS THE *** WRONG WORD ***.

In fact it's ADDITION of waveforms, not cancellation.

Graham

But d'y'see, dear old Poopster, the total harmonic distortion is less,
so something has been subtracted from the result. The net sense is the
same as cancellation. A little algebra, if you can handle it, would
help.

Or a little, a very little sensitivity to the English language would
help you arrive at the same conclusion just from reading the
explanations from Patrick and Pearcey and even Arny getting it right
for once.

Andre Jute
The anti-pedant

Output classes A and AB
 

On Oct 26, 10:06 am, Eeyore
wrote:
Patrick Turner wrote:
One cannot have distortion cancelling by one tube cancelling that in
another when one is cut off.

THANK YOU !

Basics do matter.

Graham

Here's a basic you should learn off by heart, Poopie:

Class A operation requires a limited signal so that the device(s) are
never driven to any point where they can stop conducting.

Andre Jute
Always ready to help a newbie

Output classes A and AB
 

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

This also means that once the Ia travels below 10% of the idle value,
the gm of the tube cutting off
has diminished to such a low value the other tube turning on harder is
providing virtually all the Ichange x Vchange
across the available load, and is the only device coupled through only
1/2 the OPT primary
to the load, so the RL seen by this tube turning on hard has reduced to
1/2 its class A load,
or 1/4 of the nominal RL a-a, and in this case its 1.25k.

The load is the same as that for a class B amp.

Isn't 1.25k too low a load for getting maximum power from a KT88 in
triode mode, even in class B?

No.

If the RL a-a = 5k, then the class B load is 1.25k,
and if Ea = 500V, then max Ia at grid current is about 220mA.
If you run AB2, you get a heck of a lot more Ia up to around 350mA.
KT88 ca easily make 500mA, depending on loads etc.
One can get 140W from a pair in AB2 in tetrode.

But I was asking about the best load for a class B triode amp, is 1.25k
too low for a KT-88? I guess I will have to see if I can find the
triode plate curves for the KT-88, or maybe I can substitute the 6550
curves.

There is no best load for a class B triode amp. Class B is a horrid way
to build any amp.

Maybe you meant low bias class AB.

Do the load line analysis, or have a look at my website pages and print
out a set of curves for 6550
which are virtually the same as KT88.

http://www.turneraudio.com.au/loadma...p-triodes.html



What is all this talk about ARC's anyone else's rules that would keep
you from handing out free copies of their abominable concoctious junk,
assuming you drew the schematic your self? You mentioned this same
issue in connection with the ManleyLabs amplifier you modified, my
understanding is that they only have protection for schematics they have
drawn, if you draw your own schematic of the same circuit, they have no
rights with regard to it. Any Lawyers out there care to comment?

I fell OK about just letting folks know what they could do
to rebuild a Manley or ARC or start from scratch and use the schematic I
will be posting
at my site.
There is nothing I can gain by posting a copy of the original schematic
these companies use.

I was not talking about the original schematic drawn by these companies,
I was talking about a schematic of the same circuit that you or anyone
else may have drawn, it is my understanding that there is nothing to
prevent you from legally posting such a schematic, illustrating the same
circuit as the company circuit, you just can't post the schematic drawn
by the company.

I have zero reason or time available to re-draw anyone else's original
schematic,
and have no wish to disturb the minds of the ppl who work in prestigious
US audio companies
any more than I may have. But I doubt they are aware of my existance.
What I have to say is aimed really at those with a really keen interest
in such matters AND
who understand such things AND who can read a schematic AND understand
the effects of layouts,
AND who have time to use a soldering iron.

Maybe only 2.69 people in the world are actually interested....

Many companies do NOT like ppl posting copies of their schematics on the
web,
and I have no intention of offending them by doing so.

I am not suggesting that you should do it, but it is my understanding
that they have no say in your posting a schematic you drew of their
circuit.

It would be ungentlemanly for me to copy out and post a schematic of
theirs without their consent
especially if basically I was doing it to tell everyone what a POS it
was.

Its better for them, me, and the public if I merely leave out POS
descriptions,
and say "Here's an alternative that works better than the original..."
Then anyone really keen can focus in on it, and maybe do the same thing
for themeselves,
or hire me or somebody else to do similar. I am only trying to get other
maker's gear
to stop smoking and sing better.

I have now accumulated several schematics used in a range of PP amps and
they are worth publishing
at my website when I have time because they are fine tested designs for
anyone to try.

Of course you are going to offend them by doing that, and they
may retaliate by denying you access to replacement parts.

I am free to post alternative schematics used in the cases of their amps
though,

You are also free to post your rendition of the schematic for their
original circuit.

The schematic I have come up with for some of these amps is totally
mine,
and to use my design instad of the original meant removal of 80% of the
parts and tracks on the board and starting
all over again.

As I understand the situation they only have rights
to and control over their drawing of the original circuit, you are free
to create and distribute copies of a new drawing of the circuit that was
drawn by you.

I may have that right as you suggest, but I don't feel its right to copy
their schematic
out slightly differently in appearance and post it.

The intellectual content IS THEIRS, and remains theirs even after I have
drawn it up
myself.

So if anyone wants to see really what I am on about, they have to find
their own copy of the original schematic.
To get that you have to own one of their amps and be able to quote a
serial number.

I am not in the mood to be seen to publically question all these
companies might do.
I need only say what I have done in response to being presented with
samples of their amps that
had bad smoking habits.

In general, its my personal opinion that major US companies have
forgotten how to
build simple fine amplifiers, and have drifted to complexity, weight,
size,
high cost, and lots of do-dahs and bells and whistles that do nothing
for the sound.
Meanwhile, in general, there is an appalling lack of respect for good
biasing methods
of output tubes.
Their engineers seem to have misplaced optimism about reliability in
power amps.
There is never any active protection. But ****e happens anyway.....

I shouldn't ever have to be telephoned by someone saying to me "My nice
new
brand XXX tube amp was "fixed" elsewhere, but pharqued up again a
fortnight later
and the sound went really bad, and it blows fuses..."

But most of my last 12 months work was with ppl having to cope with
results of so called engineers.

I respect engineers in general, but so often its a dumb apprentice who
is used to design the amp
in way too little time. Sales are down, and engineers cost serious
money.
Engineers are professionals, and unlike tradesmen like myself they put
an extra faerking zero on the prices they charge.
Companies only hire them if the cost can be justified by the sales
figures.

And sales by US majors are probably falling as ppl turn to chinese crap
imports.

I make no apology for my cynicism.

Patrick Turner.



Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Output classes A and AB
 

Eeyore wrote:

Patrick Turner wrote:

One cannot have distortion cancelling by one tube cancelling that in
another when one is cut off.

THANK YOU !

Basics do matter.

But Graham, once the tubes stop cancelling each other's even order
distortions
when they move from class A to AB, their non linear current behaviour is
utterly
attrocious, and each tube only 1/2 amplicates the signal.

Yet the VOLTAGE outcome across the OPT primary is substantially linear.

So some would say that by means of the SUMMING action of the OPT, there
is cancelling going on.
I am simply saying the summing action merely obstructs the gross non
linearity of currents
from being current in the OPT secondary.

Its Mysterious, this whole simple business.

But any AB amp can be made to be a class A amp if the load value is
simply raised high enough
to prevent cut off occuring, which I define as being the reduction in Ia
to less than 1/10 of
the idle current for each tube.
Cut off could also be described as being where distortion in current
waves in each tube
exceeds 5% to 10%.

Patrick Turner.


Graham

Output classes A and AB
 

Eeyore wrote:

Patrick Turner wrote:

But the SUM of the joint action of each tube in
class AB with very non linear currents
gives a linear voltage outcome.

And should not be confused with genuine CANCELLATION of distortion by Class A
push-pull operation.

Agreed, and see my last post.

Patrick Turner.

Graham

Output classes A and AB
 

John Byrns wrote:

In article ,
Eeyore wrote:

Patrick Turner wrote:

One cannot have distortion cancelling by one tube cancelling that in
another when one is cut off.

THANK YOU !

Basics do matter.

Indeed they do, but neither Patrick, myself, or anyone else is correct
on every issue. In this case Patrick has vigorously asserted that this
view, which he holds in common with you, is true, but he has failed to
even attempt an argument that might demonstrate its truth. Patrick is
an extremely skilled and talented fellow in the practical aspects of
tube amp design and construction, but he has a very limited
understanding of what is going on behind the scenes in the theory of
tube amp operation.

I think my website might indicate that your are not quite right about my
levels of understanding.

I should not mention whether or not I should be worried about your
levels of understanding.

I just let ppl decide for themseleves.

But I do know what is going on in each output tube of an AB pair,
milisecond by milisecond,
electron by electron.

Patrick Turner.





Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Output classes A and AB
 

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

This also means that once the Ia travels below 10% of the idle value,
the gm of the tube cutting off
has diminished to such a low value the other tube turning on harder
is
providing virtually all the Ichange x Vchange
across the available load, and is the only device coupled through
only
1/2 the OPT primary
to the load, so the RL seen by this tube turning on hard has reduced
to
1/2 its class A load,
or 1/4 of the nominal RL a-a, and in this case its 1.25k.

The load is the same as that for a class B amp.

Isn't 1.25k too low a load for getting maximum power from a KT88 in
triode mode, even in class B?

No.

If the RL a-a = 5k, then the class B load is 1.25k,
and if Ea = 500V, then max Ia at grid current is about 220mA.
If you run AB2, you get a heck of a lot more Ia up to around 350mA.
KT88 ca easily make 500mA, depending on loads etc.
One can get 140W from a pair in AB2 in tetrode.

But I was asking about the best load for a class B triode amp, is 1.25k
too low for a KT-88? I guess I will have to see if I can find the
triode plate curves for the KT-88, or maybe I can substitute the 6550
curves.

There is no best load for a class B triode amp. Class B is a horrid way
to build any amp.

That is certainly a broad brush stroke, McIntosh did a nice business in
what were essentially class B amplifiers. Many of the older readers
here enjoyed Rock & Roll music during their teen years delivered via the
class B amplifier at the local AM radio station, without "horrid"
results.

Maybe you meant low bias class AB.

No, I actually meant class B.

Do the load line analysis, or have a look at my website pages and print
out a set of curves for 6550
which are virtually the same as KT88.

http://www.turneraudio.com.au/loadma...p-triodes.html

I did the analysis as I earlier had said that I would. 1.25k does seem
to be a reasonable class B load for the KT-88/6550 just as you said. I
asked the question because I have not built any amps with this tube and
am not familiar with it beyond the fact that the Quadraplex VTRs at the
Television Station where I worked as a youth had a couple dozen 6550s in
each VTR. The class B load of 1.25k seemed low to me relative to your
2.5k class A load, but I made two erroneous assumptions in asking that
question. First I didn't realize that ra for the KT-88 is as low as it
is, and second I didn't take into consideration that your class A load
line is dissipation limited rather than voltage limited as with the
class B load line.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/