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
Linear Mode
