"flipper" wrote in message
...
On Sat, 19 Aug 2006 11:47:20 +1000, "Trevor Wilson"
wrote:


"flipper" wrote in message
. ..
On Sat, 19 Aug 2006 08:33:33 +1000, "Trevor Wilson"
wrote:

snip

**It is still NFB and few deny this obvious fact. It is why you cannot
build
a triode amplifier without NFB. It's already in place.

A triode amplifier with no NFB.

**No such thing.

I gave you the circuit for one in my post, your snippage
notwithstanding.


If you mean a Triode amp with no GLOBAL NFB or added LOCAL NFB (cathode
resistors, et al), then that is a different thing. In which case, that
needs
to be spelled out.

There is no need for you to feign "if you mean" as I described the
circuit making it clear 'what I meant'. Operate a triode into a
current mirror and there is no 'feedback', global, local, or
otherwise.

**It's no longer a Triode amplifier, by the strict sense of the word, is it?
The active load is now part of the amplifier.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

paul packer said:

The opinion of somebody who abetted the nefarious machinations of Lyin'
Bwian McAssWipe is of no value to those of us who choose not to live in
your gutter, Wiecky.

Perhaps you'd like to enlighten those of us not aware of this
incident, George.

Sounds like you were napping instead of actually reading. Maybe you should
just turn down the sheets a little earlier, eh?




--

"Christians have to ... work to make the world as loving, just, and supportive as is possible."
A. Krooger, Aug. 2006

On Sat, 19 Aug 2006 02:16:56 -0400, George M. Middius cmndr
[underscore] george [at] comcast [dot] net wrote:



paul packer said:

The opinion of somebody who abetted the nefarious machinations of Lyin'
Bwian McAssWipe is of no value to those of us who choose not to live in
your gutter, Wiecky.

Perhaps you'd like to enlighten those of us not aware of this
incident, George.

Sounds like you were napping instead of actually reading. Maybe you should
just turn down the sheets a little earlier, eh?


Thanks for yet another straight answer, George.

flipper wrote:

The current mirror is not an 'active load', per see, as it does not
regulate anything (as in a constant current source) but merely
reflects the triode current into a second path.

Only if you believe the current mirror action is 100% perfect.

Graham

"Eeyore" wrote in message
...
:
:
: flipper wrote:
:
: The current mirror is not an 'active load', per see, as it does not
: regulate anything (as in a constant current source) but merely
: reflects the triode current into a second path.
:
: Only if you believe the current mirror action is 100% perfect.
:
: Graham
:

Hmm. so, where were you, when there were over 40 posts, a
link to several circuits 5 months ago on this idea ??

The only way the anode voltage can have a changing influence
by electrostatically influencing the space charge around the cathode,
is when it ^actually^ changes, eh ?
so, lock the anode voltage, he, presto, no fb, no Miller, because
the inherent fb mechanism is not used

Hybrid Circuit

Ruud Broens wrote:

"Eeyore" wrote in message
...
:
:
: flipper wrote:
:
: The current mirror is not an 'active load', per see, as it does not
: regulate anything (as in a constant current source) but merely
: reflects the triode current into a second path.
:
: Only if you believe the current mirror action is 100% perfect.
:
: Graham

Hmm. so, where were you, when there were over 40 posts, a
link to several circuits 5 months ago on this idea ??

Probably not paying attention. If there were lots of Joot and Middius posts
involved I may simply not have bothered looking.


The only way the anode voltage can have a changing influence
by electrostatically influencing the space charge around the cathode,
is when it ^actually^ changes, eh ?
so, lock the anode voltage, he, presto, no fb, no Miller, because
the inherent fb mechanism is not used

Also true in cascode circuits.

Graham

Trevor Wilson wrote:

"flipper" wrote in message
...
On Sat, 19 Aug 2006 11:47:20 +1000, "Trevor Wilson"
wrote:


"flipper" wrote in message
. ..
On Sat, 19 Aug 2006 08:33:33 +1000, "Trevor Wilson"
wrote:

snip

**It is still NFB and few deny this obvious fact. It is why you cannot
build
a triode amplifier without NFB. It's already in place.

A triode amplifier with no NFB.

**No such thing.

I gave you the circuit for one in my post, your snippage
notwithstanding.


If you mean a Triode amp with no GLOBAL NFB or added LOCAL NFB (cathode
resistors, et al), then that is a different thing. In which case, that
needs
to be spelled out.

There is no need for you to feign "if you mean" as I described the
circuit making it clear 'what I meant'. Operate a triode into a
current mirror and there is no 'feedback', global, local, or
otherwise.

**It's no longer a Triode amplifier, by the strict sense of the word, is it?
The active load is now part of the amplifier.

I routinely use a solid state CCS load for a single triode preamp gain tube or
the
input tube of a power amp.

And indeed the active CCS load makes the triode amp a hybrid.
Butt the CCS I may use is just a bjt used so that the dynamic collector
resistance
is increased from the data figure of typically 20k to about 20Meg, so that any
voltage change
at the collector does not produce any significant current change.
The huge effective collector resistance is shunted by the triode's comparitively
very low
Ra, so that any artifacts produced by the presence of the bjt are reduced
by about 3 orders of magnitude; ie, the bjt CCS acts as a totally complient
slave to the
current needs of the triode, and when there is minimal current change and
maximal voltage change
in the triode then the NFB applied within the triode is at a maximum, allowing
it to have a gain
approaching the µ on the data sheets.
This gives very low THD compared to typical R loads normally used by less keen
designers.

I suggest you view the data curves for the 6SN7, and draw the load line for
20Meg ohms through Ia = 4mA at Ea = 150V, and plot the THD for +/- 10Vrms.
Its so hard to do this accurately because there is so little THD that one must
set up
a 1/2 6SN7 and measure it with a very high input Z test probe to a THD meter.

CCS are routinely used as common cathode loads in tube circuits.
The ARC amps use depletion j-fets for CCS in cathode circuits
wherever they see fit instead of using a pentode.
The pentodes would not work as well as the depletion fets.
Ditto with bjts.
One may call such circuits hybrid, but at no point in the circuits mentioned
are SS devices used to produce voltage gain; all the circuit gain is produced
with triodes.
The active SS CCS loads remove the sonic degradation caused by resistors
because resistors load a triode to cause current change and the more current
change there
is the more distortion there is.
Go back to the data graph for 6SN7, and plot a load of 40k for the anode load.
The try RL = zero ohms, ie, no load, and that is where thd is the greatest.

Should you not understand load line analysis, read my website pages to find out
how.

Patrick Turner.




--
Trevor Wilson
www.rageaudio.com.au

--
Posted via a free Usenet account from http://www.teranews.com

Eeyore wrote:
" wrote:

You must not be so parochial. Think the wide web, think the world wide
training of audio professionals. They are all indebted to the great
teaching resource about negative feedback this thread represents.

I dare say you reckon you're fabulously better placed to comment on audio than a mere professional. Would you also get your next-door neighbour to perform surgery on you in view of this revalation ?

Graham
-----------------------------------------------

Dear Mr. Eeyore. It seems that I caused offence and you're leaping into
the breach to defend your profession that I supposedly attacked. Where
exactly did you see me say that I'm."...fabulously better placed to
comment on audio than a mere professional" ? On the contrary I deplored
that the assembled professionals of the RAO indulge in endless
mud-slinging contests instead of enlightening us about their job. Shall
I quote some of your own comments?
Of course the sample we get in RAO may not be representative. To
illustrate let me answer your rhetorical question: "Would you also get
your next-door neighbour to perform surgery on you in view of this
revalation ?". The answer is :Yes, given no other choice I might go for
a commonsensical neighbour rather than some "surgeons" I had seen. A
degree is a licence to practice , not a guarantee of good practice. In
medicine, unfortunately, it may be a licence to kill. As one of my
Univ. teachers used to say: "With your degree you're given a little
private cemetery and you can set out to fill it for the rest of your
professional life"
But your snippet brings in a wider issue: In the end it is the consumer
who decides. And consumer are just as varied as the engineers serving
them.
Your more primitive colleagues on RAO assure us that they represent
"Science". They "prove" that all transistors are better than all tubes,
all CDs.bettere than all LPS and that all their double-blind judgements
are better than all those of K. Rubinson's, J.Atkinson's, Gordon Holt's
etc if sighted..
There are just one or two little problems. To a layman- consumer it
appears that many leaders in your profession do not write for RAO but
are busy creating different wrinkles for amps, preamps, cd players etc.
that your "scientists" say should all sound the same. Whom to
believe? Who is the voodoo scientist: Manley and D'Agostino, or Bateman
of the RAHE and the usual shrill suspects of RAO?
If you add that these gents proclaim the infallibility of their
voodoo, magic "test" that they never bothered to validate by a properly
designed experimentation- what is the poor consumer to do but rely on
his preference?
By all means explain to us how things work but leave us with our
preferences because neither we nor you have an infallible tool to
measu better from worse.that works for anyone other than ourselves.
And keep filth out of these pages..
Ludovic Mirabel

Eeyore wrote:
" wrote:

You must not be so parochial. Think the wide web, think the world wide
training of audio professionals. They are all indebted to the great
teaching resource about negative feedback this thread represents.

I dare say you reckon you're fabulously better placed to comment on audio than a mere professional. Would you also get your next-door neighbour to perform surgery on you in view of this revalation ?

Graham

To clarify: My sarcastic comment one half of which you quoted referred
to this contribution (and its like):: "Now, which bothers you more?
That as a sockpuppet, McCoy's fingers are
so far up your fundament that you are tasting them from the back of
your throat, or that you are only its second-favorite?"
Or do you think it is a "comment from a professional" for us peasants?
My desire to keep the filth out of RAO did not refer to you.
Ludovic Mirabel

" wrote:

Eeyore wrote:
" wrote:

You must not be so parochial. Think the wide web, think the world wide
training of audio professionals. They are all indebted to the great
teaching resource about negative feedback this thread represents.

I dare say you reckon you're fabulously better placed to comment on audio than a mere professional. Would you also get your next-door neighbour to perform surgery on you in view of this revalation ?

Graham

To clarify: My sarcastic comment one half of which you quoted referred
to this contribution (and its like):: "Now, which bothers you more?
That as a sockpuppet, McCoy's fingers are
so far up your fundament that you are tasting them from the back of
your throat, or that you are only its second-favorite?"
Or do you think it is a "comment from a professional" for us peasants?
My desire to keep the filth out of RAO did not refer to you.
Ludovic Mirabel

It was the intimation that audio professionals had somehow to be brainwashed to 'believe' in NFB. I've done the circuit theory of its application at college. It's no more good or bad than V=IR !

Graham