Can anybody please explain what does biasing of the tubes mean?
What does balanced or single ended mean?

I apologize for the boder
Thank you

In article AMiOb.76173$5V2.92278@attbi_s53, Arcam EAD Man
wrote:

Can anybody please explain what does biasing of the tubes mean?

Bias is a back-ground voltage that is required to get a tube or
transistor to turn on and start running. With a transistor, this
is normally a base to emitter voltage of about 6/10's of a volt.
I don't know what is typical for a tube, but I would suspect that
it is cathode to grid, and it could many tens of volts, perhaps a
negative voltage.

What does balanced or single ended mean?

Single ended means a single transmission cable (or other device)
where one side of the output is ground, and the other side is
the signal. Balanced means that the signal floats between to
wires in a cable, and neither one is grounded. You normally
get balanced output from a transformer, whereas coaxial cables
are normally single ended (center is signal, shield is ground).
Just to confuse things, there are coax cable types that have
a twisted pair in the center for handling balanced signals.
The common place that you see balanced signals is with microphones.

-john-

--
================================================== ==================
John A. Weeks III 952-432-2708
Newave Communications http://www.johnweeks.com
================================================== ==================

http://www.aikenamps.com/WhatIsBiasing.htm

I think a balanced tube amp means there's at least
two power output tubes, and just one with a
single-ended design, but I'm not totally sure
about that.

/jim


Arcam EAD Man wrote:
Can anybody please explain what does biasing of the tubes mean?
What does balanced or single ended mean?

I apologize for the boder
Thank you

Arcam EAD Man wrote:

Can anybody please explain what does biasing of the tubes mean?

Biasing is a voltage applied to the grid of a vacuum tube that sets the
"operating condition" - meaning the quiescent current that flows through
the tube.

Some tubes require a negative voltage with respect to the cathode in
order to start off in mostly *turned off* state - whereupon the signal
can cause the tube to turn *on*. Other tubes are mechanically and
electrically built so that they are *without the application of external
bias voltage* mostly *off*. These are called "zero bias" or "class B"
(referring to the amplification class) tubes.

Tubes work by being turned on and off by a signal (AC). Class A
is nominally considered to be 50% on (or 50% off) - so the signal
can drive the tube up to full on, and off to full off (nominally).

So the operation of the tube *must* be properly set before the
signal is applied.




What does balanced or single ended mean?

In terms of amplifiers, you mean Push-Pull or Single-ended.
In terms of cables "balanced" means a two phase (positive
and inverted) plus ground signal path. Single ended in cables
means one signal path and ground (like an RCA-RCA cable)

In amps push-pull is two or more tubes (pairs) each working
across a load (or transformer connected to a load) in opposite
phase...

This is easy to remember as follows:

Single-ended: one guy pushing and pulling one of those big old
lumberjack saws
Parallel Single-ended: two or more guys on the *same side* of
that saw
Push pull: two guys one on each side of the saw (note how one
pulls, when the other pushes?)
(the above is Class A P-P)
Push-Pull class B: two guys one on each side of the saw; one
pulls, then the other pulls - *neither pushes*

Now you know everything you need to know about it!

_-_-bear



I apologize for the boder
Thank you

--
_-_- BEAR Labs
- Custom Audio Equipment, Cables, Mods, Repairs -
http://www.bearlabs.com

John A. Weeks III wrote:

In article AMiOb.76173$5V2.92278@attbi_s53, Arcam EAD Man
wrote:


Can anybody please explain what does biasing of the tubes mean?


Bias is a back-ground voltage that is required to get a tube or
transistor to turn on and start running. With a transistor, this
is normally a base to emitter voltage of about 6/10's of a volt.
I don't know what is typical for a tube, but I would suspect that
it is cathode to grid, and it could many tens of volts, perhaps a
negative voltage.
====================================

Grid negative relative to cathode, generally in the 30 volt range.

-GP

BEAR wrote in message ...
Arcam EAD Man wrote:

Can anybody please explain what does biasing of the tubes mean?

So the operation of the tube *must* be properly set before the
signal is applied.
What does balanced or single ended mean?

In terms of amplifiers, you mean Push-Pull or Single-ended.
In terms of cables "balanced" means a two phase (positive
and inverted) plus ground signal path. Single ended in cables
means one signal path and ground (like an RCA-RCA cable)

In amps push-pull is two or more tubes (pairs) each working
across a load (or transformer connected to a load) in opposite
phase...

This is easy to remember as follows:

Single-ended: one guy pushing and pulling one of those big old
lumberjack saws
Parallel Single-ended: two or more guys on the *same side* of
that saw
Push pull: two guys one on each side of the saw (note how one
pulls, when the other pushes?)
(the above is Class A P-P)
Push-Pull class B: two guys one on each side of the saw; one
pulls, then the other pulls - *neither pushes*

CLose analogy, and a good one, but I think it needs correction.

Single ended: the saw is ALWAYS handled by one guy on one
side of the saw
Push-pull: There's a guy at each end of the saw.

Class A: The saw is pushed ALL the way from one end of the
stroke to the other end, then all the way back
again
Class B: The saw is pushed all the way from one end of
the stroke to the middle, and then whoever is
pushing stops, waits however long it might take
the saw to normally mopve the rest of the distance,
and pulls it back when it's time to.

Now, combining the two analogies, a Class A push-pull amplifier
is like a a gang saw with a person at either end, and both push
and pull the entir stroke.

A class B push-pull amplifier has the guy on the left push
the saw to the right exactly to the middle. He lets go the
instant the guy on the right grabs it and continues pulling it.
The guy on the right pulls it all the way to the right, then
pushes it back to the middle and, at just the right instant, lets
go as the guy on the left grabs it and pulls it the rest of the
way. Each sawyer does only his have of the work and absolutely
nothing more or less

And, in between, you have the Class-AB gang-saw where each worker
pushes beyond the halfway point, but eventually relinuishes the
saw for somewhat less than all but more than half of the work.

In linear audio amplification, ALL single-ended amplification
application had better be Class-A or large amounts of distortion
will result. In push-pull applications, Class-A, AB or B are
all usable, but Class B requires very precise control of the bias
point.

Now, using all this analogy stuff, imagine "bias" as the instructions
to each sawyer as to when push or pull and when not to.