Estimating Power Output For A Class A1 Amplifier From Valve Specifications
In class A, in order to produce a full sine wave, the tube must be exactly half-way on. Therefore the maximum current swing is +/- 50%. No actual amplifier will ever achieve this.
Obtain the following parameters:
- Pa (or P for pentodes) (in watts).
- Rp in triode (in ohms),
- load resistance (Rl) (in ohms) (which may vary depending on the design.)
Compute maximum theoretical power output by P = Pa / 2.
While the valve can be driven all the way to shut-off fairly easily, the maximum current will be limited by the internal resistance of the valve as the grid reaches the voltage of the cathode and is not impeding electron flow. For this reason, valves that have a low Rp can yield more power in class A1 than other valves with similar Pa ratings.
Next, compute P = P * (1 - Rp/Rl) to obtain an estimate of the maximum obtainable output power.
Deduct 10% from this figure to account for the relatively heavy distortion encountered as the valve approaches cut-off.
Read more about this topic: Single-ended Triode
Famous quotes containing the words estimating, power, output and/or class:
“I am sure that in estimating every man’s value either in private or public life, a pure integrity is the quality we take first into calculation, and that learning and talents are only the second.”
—Thomas Jefferson (1743–1826)
“The importance of a lost romantic vision should not be underestimated. In such a vision is power as well as joy. In it is meaning. Life is flat, barren, zestless, if one can find one’s lost vision nowhere.”
—Sarah Patton Boyle, U.S. civil rights activist and author. The Desegregated Heart, part 1, ch. 19 (1962)
“Lizzie Borden took an axe
And gave her mother forty whacks;
When she saw what she had done,
She gave her father forty-one.”
—Anonymous. Late 19th century ballad.
The quatrain refers to the famous case of Lizzie Borden, tried for the murder of her father and stepmother on Aug. 4, 1892, in Fall River, Massachusetts. Though she was found innocent, there were many who contested the verdict, occasioning a prodigious output of articles and books, including, most recently, Frank Spiering’s Lizzie (1985)
“There might be a class of beings, human once, but now to humanity invisible, for whose scrutiny, and for whose refined appreciation of the beautiful, more especially than for our own, had been set in order by God the great landscape-garden of the whole earth.”
—Edgar Allan Poe (1809–1849)