Want a better understanding how an amp works

[analogman]

 

Typing on a tablet makes me try to conserve words.

 

You'd never know it

 

[WMcD]

I get annoyed when self appointed experts (young loudmouths, typically) say things like: I can hear wire and I can hear solder.  My point is that there is solder and wire in every step of the analog recording, mixing, storage, playback, preamp, and power amp.  Whatever they have in their living room is just the final step.  If they say they can hear wire and solder you have to wonder if they can here wire and solder in, e.g. that mixing board.

 

There is a bit of that in the subject we're talking about.  Maybe in a good way.  The power amps we're talking about are running in Class A mode with an SET.  the device is always turned on.  When there I silence, the tube is conducting current through the transformer sort of at half power (current) for the tube.

 

At every step along the way from microphone to your power amp, the tubes or transistor in the equipment are also running Class A, although the coupling is rarely a transformer but rather a capacitor.  So we're listening to a lot of Class A amps in the music.

 

Of course now, maybe there is a digital converter in the microphone pre-amp.  But in the old days, it was all Class A.

 

An exception may be the record cutter.  I expect they used push pull amps.  Nelson Pass (IIRC) converted one to be powered by one of this big Class A power amps.

 

WMcD.

[djk]

" When there I silence, the tube is conducting current through the transformer sort of at half power (current) for the tube."

 

With the SET the current is at full all the time, with push-pull class A it's at half power.

[russ69]

" When there I silence, the tube is conducting current through the transformer sort of at half power (current) for the tube."

 

With the SET the current is at full all the time, with push-pull class A it's at half power.

5500 posts and you don't know how to quote or are you device limited?

[babadono]

At every step along the way from microphone to your power amp, the tubes or transistor in the equipment are also running Class A, although the coupling is rarely a transformer but rather a capacitor. So we're listening to a lot of Class A amps in the music.

Class A? Every step? Are you sure about that?

[djk]

"5500 posts and you don't know how to quote or are you device limited"

 

I post from work, and the computers in the 'resource room' barely work.
 

[WMcD]

 

At every step along the way from microphone to your power amp, the tubes or transistor in the equipment are also running Class A, although the coupling is rarely a transformer but rather a capacitor. So we're listening to a lot of Class A amps in the music.

Class A? Every step? Are you sure about that?

 

Sorry here:  Ann Landers wrote, "All generalizations are false, including this one."  Smile.

 

I should have considered the widely used op-amps.  A 741 is popular.  I looked it up on Wikipedia.

 

http://en.wikipedia.org/wiki/Operational_amplifier

 

It says the output stage (actually a buffer to provide a lower output impedance and higher current is an AB push pull. 

 

We can't really know everything our music has gone through. 

 

WMcD

 

 

[WMcD]

" When there I silence, the tube is conducting current through the transformer sort of at half power (current) for the tube."

 

With the SET the current is at full all the time, with push-pull class A it's at half power.

Perhaps we are talking about different things.

 

In my view, the current through the tube varies in accord to the music.  Suppose we apply a sine wave of input.  At the bottom of the sine wave the current is 10 mA, at the middle or zero crossing it is 20 mA, at the top it is 30 mA.  (Just to pick some numbers.)  This current goes through the primary winding of the output transformer. 

 

Therefore, the tube is not fully conducting all the time.

 

WMcD

[seanwalsh]

When I switch to 45 tube from 2a3, I must drop a transformer tap to change reflected impedance,What is reflected impedance? It is an ASL Orchid DT not a tulip. It sounds best off the 8 ohm tap for both tubes,

[seanwalsh]

The la Scalas are mostly 6 to 12 ohms. How does the transformer cope with this demand?

[seanwalsh]

I always have too many amps and set and sep have never been favored. With the la scalas this 2a3 sounds best despite reason. Just wondering...