Output classes A and AB
 

Multi-grid wrote:

A properly designed Class A amp
never clips because the operating parameters were so chosen that it
runs out of signal from the intended source before it can clip (that
is one reason why the design instructions on my netsite feature the
*design center* process so heavily).

Stay on topic please.

While you're at it, please refrain from making personal attacks, it is
beneath you( I hope ).

Class A has nothing to do with its input signal. The finals clip
symetrically. Or perhaps unsymetrically if it is power limited A, so
to say overbiased given the load and B+. If you have plate dissipation
to spare, it is certainly possible. Matter of fact I am listening to
one such amp now...:)
cheers,
Douglas

I believe the point it changes from 'class A' to 'class AB' is commonly
accepted to be the point where the output stage begins to draw more
current from the power supply. By commonly accepted, I mean I've read a
ton of magazine reviews of tube amps where they use this logic, stated
almost exactly as Andre has used it.

In other words, the amp is biased a bit hotter than class B, and this
lowers low level distortion a bit at the expense of peak power output.

Stating that "the amplifier is Class A until XXX watts", really, is
telling you how hot the tubes are biased relative to the two extremes of
pure class A (full dissapation), and pure class (cut off).

Output classes A and AB
 

In article . com,
Andre Jute wrote:

On Oct 22, 2:33 pm, mick wrote:
On Mon, 22 Oct 2007 13:50:47 -0700, Multi-grid wrote:

snip

So then Andre, you mention an AB amp having A power, you reference an
80W SE amp, claim an off the rack Vellman kit is brilliant, and then
attack anybody who'd have the guts to say you've over reached. Even with
poor S/N ratio there is still signal. Let's see some from you. cheers,

Who is this fellow "Multi-grid", and why is he addressing me?

Hi Andre,

This fellow "Multi-grid" is either a Troll, ignorant, or most likely
both, his goal appears to be trying to stir up trouble so he is best
ignored.


Regards,

John Byrns

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

Output classes A and AB
 

On Oct 23, 6:01 am, maxhifi wrote:
Multi-grid wrote:
A properly designed Class A amp
never clips because the operating parameters were so chosen that it
runs out of signal from the intended source before it can clip (that
is one reason why the design instructions on my netsite feature the
*design center* process so heavily).

Stay on topic please.

While you're at it, please refrain from making personal attacks, it is
beneath you( I hope ).

Class A has nothing to do with its input signal. The finals clip
symetrically. Or perhaps unsymetrically if it is power limited A, so
to say overbiased given the load and B+. If you have plate dissipation
to spare, it is certainly possible. Matter of fact I am listening to
one such amp now...:)
cheers,
Douglas

I believe the point it changes from 'class A' to 'class AB' is commonly
accepted to be the point where the output stage begins to draw more
current from the power supply. By commonly accepted, I mean I've read a
ton of magazine reviews of tube amps where they use this logic, stated
almost exactly as Andre has used it.

In other words, the amp is biased a bit hotter than class B, and this
lowers low level distortion a bit at the expense of peak power output.

Stating that "the amplifier is Class A until XXX watts", really, is
telling you how hot the tubes are biased relative to the two extremes of
pure class A (full dissapation), and pure class (cut off).- Hide quoted text -

- Show quoted text -

Class A has nothing to do with dissipation either. Just because some
marketing group noticed that class A means something good, does not
make it right either. Just because it seems to make sense is no reason
to *******ize the definition. Find some other way to describe it.
cheers,
Douglas

Output classes A and AB
 

On Oct 23, 6:33 am, John Byrns wrote:
In article . com,
Andre Jute wrote:

On Oct 22, 2:33 pm, mick wrote:
On Mon, 22 Oct 2007 13:50:47 -0700, Multi-grid wrote:

snip

So then Andre, you mention an AB amp having A power, you reference an
80W SE amp, claim an off the rack Vellman kit is brilliant, and then
attack anybody who'd have the guts to say you've over reached. Even with
poor S/N ratio there is still signal. Let's see some from you. cheers,

Who is this fellow "Multi-grid", and why is he addressing me?

Hi Andre,

This fellow "Multi-grid" is either a Troll, ignorant, or most likely
both, his goal appears to be trying to stir up trouble so he is best
ignored.

Regards,

John Byrns

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

It appears you folks are living up to your reputation for making
personal attacks. It isn't this:
That sort of street
corner gossip repeated as gospel is what trashes the reputation of
RAT, not putting down the thieves of intellectual rights or
netbullies
and netstalkers -- on the contrary, it is toleration and protection
of
such people that trashes our reputation.

that's doing RAT harm. Getting nasty on the other hand...
cheers,
Douglas

Output classes A and AB
 

On Oct 22, 11:33 pm, John Byrns wrote:

This fellow "Multi-grid" is either a Troll, ignorant, or most likely
both, his goal appears to be trying to stir up trouble so he is best
ignored.

Ever ready with the diaper, John?

Peter Wieck
Wyncote, PA

Output classes A and AB
 

Multi-grid wrote:

maxhifi wrote:

Stating that "the amplifier is Class A until XXX watts", really, is
telling you how hot the tubes are biased relative to the two extremes of
pure class A (full dissapation), and pure class (cut off).- Hide quoted text -


Class A has nothing to do with dissipation either. Just because some
marketing group noticed that class A means something good, does not
make it right either. Just because it seems to make sense is no reason
to *******ize the definition. Find some other way to describe it.

The definition of Class A is very simple. It requires that the output device(s)
never cease conducting under any signal condition.

Graham

Output classes A and AB
 

On Tue, 23 Oct 2007 14:34:31 +0100, Eeyore wrote:

Multi-grid wrote:

maxhifi wrote:

Stating that "the amplifier is Class A until XXX watts", really, is
telling you how hot the tubes are biased relative to the two extremes
of pure class A (full dissapation), and pure class (cut off).- Hide
quoted text -


Class A has nothing to do with dissipation either. Just because some
marketing group noticed that class A means something good, does not
make it right either. Just because it seems to make sense is no reason
to *******ize the definition. Find some other way to describe it.

The definition of Class A is very simple. It requires that the output
device(s) never cease conducting under any signal condition.



Correct. A class AB amp fulfills this up to the point where one side
starts to turn off.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

Output classes A and AB
 

Multi-grid wrote:
Class A has nothing to do with dissipation either.

Then Poopie wrote:
The definition of Class A is very simple. It requires that the output
device(s) never cease conducting under any signal condition.

Then Mick http://www.nascom.info and http://mixpix.batcave.net wrote:
Correct. A class AB amp fulfills this up to the point where one side
starts to turn off.

I can see what you're getting at, Poopie, and so can Mick apparently,
but I don't think I want to wear your definition where it says "under
any signal condition". That's most misleading, especially with a
newbie on the board who stubbornly keeps claiming signal has nothing
to do with Class A. Any power stage that is hitherto Class A can
driven to cutoff by simply increasing the signal until the output cuts
out at either zero current or zero voltage.

In any and all cases, Class A is defined, though usually implicitly
rather than explcitly, as at a particular, *limited* signal voltage. I
therefore prefer the definition of Class A which says simply:
***Class A operating conditions do not permit the output device to
cease conducting.***
If you insist on describing the signal condition, you could add the
words *at the design or intended or specified signal*.

As for Dougles Multi-grid's silly insistence that signal and
dissipation have nothing to do with Class A operation, thanks for the
giggle, sonny, but you'd better hit the books lots more before you
seek entry to this club. In particular, you should pay attention to
this, which often comes as a bolt from the blue to repair hacks like
you, who tend to assume that the parameters are godgiven and fixed:
the *designer* chooses the plate voltage and negative bias, that sets
the current at quiescence, through which the designer then runs the
loadline at a particular angle when he chooses a primary impedance for
his output transformer, the slope of the loadline determining how far
the quiescent point is from current cutoff (or voltage cutoff...), and
that in turn defines the signal voltage that can be put in for Class A
operation, which in turn defines the output power. Thus the signal
level has everything to do with Class A operation, and in turn defines
maximum possible dissipation from Class A operation. Cruise my
netsite; all this is explained in both words and pictures.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Output classes A and AB
 

On Oct 23, 3:37 pm, Andre Jute wrote:
Multi-grid wrote:
Class A has nothing to do with dissipation either.
Then Poopie wrote:
The definition of Class A is very simple. It requires that the output
device(s) never cease conducting under any signal condition.

Then Mickhttp://www.nascom.infoandhttp://mixpix.batcave.netwrote:

Correct. A class AB amp fulfills this up to the point where one side
starts to turn off.

I can see what you're getting at, Poopie, and so can Mick apparently,
but I don't think I want to wear your definition where it says "under
any signal condition". That's most misleading, especially with a
newbie on the board who stubbornly keeps claiming signal has nothing
to do with Class A. Any power stage that is hitherto Class A can
driven to cutoff by simply increasing the signal until the output cuts
out at either zero current or zero voltage.

In any and all cases, Class A is defined, though usually implicitly
rather than explcitly, as at a particular, *limited* signal voltage. I
therefore prefer the definition of Class A which says simply:
***Class A operating conditions do not permit the output device to
cease conducting.***
If you insist on describing the signal condition, you could add the
words *at the design or intended or specified signal*.

As for Dougles Multi-grid's silly insistence that signal and
dissipation have nothing to do with Class A operation, thanks for the
giggle, sonny, but you'd better hit the books lots more before you
seek entry to this club. In particular, you should pay attention to
this, which often comes as a bolt from the blue to repair hacks like
you, who tend to assume that the parameters are godgiven and fixed:
the *designer* chooses the plate voltage and negative bias, that sets
the current at quiescence, through which the designer then runs the
loadline at a particular angle when he chooses a primary impedance for
his output transformer, the slope of the loadline determining how far
the quiescent point is from current cutoff (or voltage cutoff...), and
that in turn defines the signal voltage that can be put in for Class A
operation, which in turn defines the output power. Thus the signal
level has everything to do with Class A operation, and in turn defines
maximum possible dissipation from Class A operation. Cruise my
netsite; all this is explained in both words and pictures.

Mmm. It occurs to me that when dealing with a newbie, even if it is
all explained on my netsite, and Patrick's, and all the textbooks, and
in Crowhurst, which Multi-grid could read with profit, I should
explain what signal voltage has to do with power output. Power is the
product of voltage and current. The bigger the voltage and current
swing, the greater the power output (for a given load). The plate
voltage and current swing is proportional to the size of the signal
working through mu, the amplification factor of the tube. Thus the
greater the signal that can be put in under a particular class of
operation, in this case Class A, the greater the voltage swing and the
more the current change between the peaks of the signal, the bigger
the product of voltage and current, and the greater the power. So, you
see, sonny, in Class A operation, which is in any event very
inefficient, the amount of space the designer allows for signal to
swing without breaching Class A conditions determines the entire
outcome. The same applies to Class AB, where the signal-travel the
designer has arranged (by his choice of plate voltage and negative
grid bias and primary impedance) during which current is not cut off
determines how much of the output can be in Class A, with the rest by
definition in Class B.

Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Output classes A and AB
 

On Oct 24, 2:56 am, Andre Jute wrote:
On Oct 23, 3:37 pm, Andre Jute wrote:





Multi-grid wrote:
Class A has nothing to do with dissipation either.
Then Poopie wrote:
The definition of Class A is very simple. It requires that the output
device(s) never cease conducting under any signal condition.

Then Mickhttp://www.nascom.infoandhttp://mixpix.batcave.netwrote:

Correct. A class AB amp fulfills this up to the point where one side
starts to turn off.

I can see what you're getting at, Poopie, and so can Mick apparently,
but I don't think I want to wear your definition where it says "under
any signal condition". That's most misleading, especially with a
newbie on the board who stubbornly keeps claiming signal has nothing
to do with Class A. Any power stage that is hitherto Class A can
driven to cutoff by simply increasing the signal until the output cuts
out at either zero current or zero voltage.

In any and all cases, Class A is defined, though usually implicitly
rather than explcitly, as at a particular, *limited* signal voltage. I
therefore prefer the definition of Class A which says simply:
***Class A operating conditions do not permit the output device to
cease conducting.***
If you insist on describing the signal condition, you could add the
words *at the design or intended or specified signal*.

As for Dougles Multi-grid's silly insistence that signal and
dissipation have nothing to do with Class A operation, thanks for the
giggle, sonny, but you'd better hit the books lots more before you
seek entry to this club. In particular, you should pay attention to
this, which often comes as a bolt from the blue to repair hacks like
you, who tend to assume that the parameters are godgiven and fixed:
the *designer* chooses the plate voltage and negative bias, that sets
the current at quiescence, through which the designer then runs the
loadline at a particular angle when he chooses a primary impedance for
his output transformer, the slope of the loadline determining how far
the quiescent point is from current cutoff (or voltage cutoff...), and
that in turn defines the signal voltage that can be put in for Class A
operation, which in turn defines the output power. Thus the signal
level has everything to do with Class A operation, and in turn defines
maximum possible dissipation from Class A operation. Cruise my
netsite; all this is explained in both words and pictures.

Mmm. It occurs to me that when dealing with a newbie, even if it is
all explained on my netsite, and Patrick's, and all the textbooks, and
in Crowhurst, which Multi-grid could read with profit, I should
explain what signal voltage has to do with power output. Power is the
product of voltage and current. The bigger the voltage and current
swing, the greater the power output (for a given load). The plate
voltage and current swing is proportional to the size of the signal
working through mu, the amplification factor of the tube. Thus the
greater the signal that can be put in under a particular class of
operation, in this case Class A, the greater the voltage swing and the
more the current change between the peaks of the signal, the bigger
the product of voltage and current, and the greater the power. So, you
see, sonny, in Class A operation, which is in any event very
inefficient, the amount of space the designer allows for signal to
swing without breaching Class A conditions determines the entire
outcome. The same applies to Class AB, where the signal-travel the
designer has arranged (by his choice of plate voltage and negative
grid bias and primary impedance) during which current is not cut off
determines how much of the output can be in Class A, with the rest by
definition in Class B.



Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

keep repeating yourself, it may come true sometime.

In the meantime, some additional proof besides the circular stuff you
keep digging up might show you the holes in your arguement. As to
Crowhurst, his creativity outstripped his ability to write
unequivocally.

While you're digging, why not produce some documentation of the 80W SE
amp you mentioned earlier.
cheers,
Douglas