Quantum 2.00 Tips Part 1

[dr bonkers]

A prize to the person who can explain why "Class A" amps don't sag much.

Is it because in true "Class A" design, the tubes are on for the entire waveform?

By contrast in "Class B", a given tube is on for only the positive or negative portion of the waveform and in the intierim, the tube goes into an idle state.

Class AB uses some overlap between the tubes that act on the positive or negative portions of the waveform, so the tubes are at some point going into an idle state..

So Class A has a more constant draw on the power supply versus the other classes due to less lapses into an idle state when amplifying the signal.

Did I remember this correctly?

 

[greiswig]

A prize to the person who can explain why "Class A" amps don't sag much.

Is it because in class A, the power tubes are already drawing all the current they will draw, so in essence they are "pre-sagged?"

Thanks for the info.

 

[DukeOfPrunes]

A prize to the person who can explain why "Class A" amps don't sag much.

By definition, Class A amps have relatively constant drain on current, whereas Sag refers to the drooping of the power supply voltage in response to large transient signals, which lends a certain dynamic "feel" to the tube amplifier that is not generally pronounced in Class A amplifiers. (lifted from Aiken amplification.)

 

[Stadanko]

A prize to the person who can explain why "Class A" amps don't sag much.

True class A amplifiers have no sag because the current draw at full power is the same as the current draw at idle. Most class A amplifiers aren't biased exactly at the midpoint of the range, and will tend to clip asymmetrically. There will be an offset current component, but it will be much smaller than in a class AB output stage.

From aiken


If this is indeed what you were looking for in an answer, it was too easy to find. something with more complex research requirements would be a good test of ones resolve. Most of us won't know this off of the top of our heads.

 

[bdrepko]

FractalAudio said: ↑
A prize to the person who can explain why "Class A" amps don't sag much.

The dimmer-squeegee prevents reverse current to the darkness emitting diode (DED).

 

[Black Bitch]

No winner yet?

 

[Ed DeGenaro]

cause they draw max current at idle...hence single ended amps with tube rectifiers almost feel like they have the opposite of sag...

 

[Patzag]

Because they use Playtex Cross My Heart bras

 

[Sleestak]

This is great information! Thank you.

 

[Xrocker]

A "class a" silicon implant will prevent sag for many years!

 

[cakewalkgg]

Love this.. thank you for detailing this out!

 

[REDD]

A prize to the person who can explain why "Class A" amps don't sag much.

They are too classy for that saggy stuff.

 

[Brownmatthall]

A prize to the person who can explain why "Class A" amps don't sag much.

Botox?

 

[LPaulasBestFriend]

Wooden implants?
Gives a fine Mahogany feeling!

 

[Hyper Planet]

Thank you very much indeed

 

[FractalAudio]

Silicon sags less...

 

[RDH]

Silicon sags less...

Darn it! I was gonna say that!

 

[VegasGuitar]

Power Supply:

Tube Bias controls the idle current of the virtual power tubes. ....

Is there an equivalency ratio, or calculation that would allow one to use Tube Bias to equal a particular idle current, say 25 mA?

 

[bobmichigan]

The Axe-Fx is truly a new epoch in guitar toneology.

 

[Rexxyboy]

Thanks Cliff, a great read. I know nothng about amp design, but as hard as i tried tweaking both suppy sag and other parameters,, i could only get the meter to reduce by -0.1 of a dB. Not saying its a bad thing, I was really excited to see a new meter on the hardware and wanted to see it go nuts, cause i just LOVE METERS! I use the VU meters in Utility all the time.