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)
“First, there is the power of the Wind, constantly exerted over the globe.... Here is an almost incalculable power at our disposal, yet how trifling the use we make of it! It only serves to turn a few mills, blow a few vessels across the ocean, and a few trivial ends besides. What a poor compliment do we pay to our indefatigable and energetic servant!”
—Henry David Thoreau (1817–1862)
“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)
“In verity ... we are the poor. This humanity we would claim for ourselves is the legacy, not only of the Enlightenment, but of the thousands and thousands of European peasants and poor townspeople who came here bringing their humanity and their sufferings with them. It is the absence of a stable upper class that is responsible for much of the vulgarity of the American scene. Should we blush before the visitor for this deficiency?”
—Mary McCarthy (1912–1989)