Was it some kind of Kelvin sense arrangement, or just one pair for each direction, or something else? The YouTube is flooded with all types of amplifier tests. You can use this conceptual framework to describe virtually anything that does something. Sign up or log in Sign up using Google. The amplification occurs by means of creating directional sound, and better match between acoustic impedance of open air and transducer membrane. Sign up to join this community.
This third electrode, called the control grid, enabled the vacuum tube to be used not just as a rectifier, but as an amplifier of electrical signals. The control grid is placed between the cathode and anode, and is in the shape of a mesh the holes allow electrons to pass through it.
By adjusting the voltage applied to the grid, you can control the number of electrons flowing from the cathode to the anode. If the grid is given a strong negative voltage, it repels the electrons from the cathode and chokes the flow of current.
The more you increase the grid voltage, the more electrons can pass through it, and the higher your current. The triode is useful for amplifying signals because a small change in the control grid voltage leads to a large change in the plate current. In this way, a small signal at the grid like a radio wave can be converted into a much larger signal, with the same exact waveform, at the plate. But why stop at three electrodes when you could have four?
Or five, for that matter? Further enhancements of vacuum tubes placed an additional grid called the screen grid and yet another called the suppressor grid even closer to the anode, creating a type of vacuum tube called a tetrode and a pentode , respectively.
These extra grids solve some stability problems and address other limitations with the triode design, but the function remains largely the same. The transistor could replicate all the functions of tubes, like switching and amplification, but was made out of semiconductor materials. Once the transistor cat was let out of the bag, vacuum tubes were on their way to extinction in all but the most specific of applications.
For example, vacuum tubes are still used in high power RF transmitters, as they can generate more power than modern semiconductor equivalents. But perhaps the most charming modern application of vacuum tubes is in the musical community.
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Current Articles Archives. The original triode vacuum tube, the Audion, invented by Lee de Forest in Image courtesy of Gregory F. A simplified diagram of a vacuum tube diode. When the cathode is heated, and a positive voltage is applied to the anode, electrons can flow from the cathode to the anode. No wonder a DSP would be hard pressed to mimic a tube guitar amplifier.
The bottom line is that tubes tend to have odd harmonic distortion because the output stages are always true class B AB actually and fully balanced [cancelling even harmonics] where transistor amplifiers tend to be quasi-class B, frequently with two NPN in the same circuit rather than trying to balance with a PNP and NPN which has its own limitations. The transfer function for transistors has pretty much all of the harmonics and the higher level odd harmonics have much higher coefficients.
At very low volume those higher level terms add almost nothing for either type amplifier, but when you run at volume level 10, those higher level terms add bunches of harmonics and especially the even numbers that the tubes and transformer tend to cancel out.
Transistors also tend to have larger coefficients for the higher terms than tubes. A High Fidelity system should be exactly that: high fidelity. If your transistor amplifier sounds like crap, it is your fault, not that of the transistors: it means your amplifier doesn't have enough head room for the desired volume or that it was just plain designed wrong.
I suspect that most systems also use speakers that are not matched to the amplifier properly.
Vacuum Tubes Versus Solid-State. The tube versus transistor debates that you hear most often occur in the pages of consumer and music magazines, with. Vacuum Tubes and Transistors Compared. Transistors vs. Tubes – Brief Feature Comparison, adapted from IEEE & Eric Barbour's “Cool Sound of Tubes”.
You mentioned damping as a part of the issue. There aren't many of those 20 year olds around and most of them are not the ones buying tube amps. Ray W5IFS. Thanks, Ray, for the elucidation. And so the discussion continues. Look for more coverage in ED on this subject in the near future.