That is not a bad analogy, and one that I have used several times to explain impedance matching.
You have an engine spinning at a few thousand RPM and a set of drive wheels spinning at a few hundred RPM. Two sets of gears in the transmission / differential transform a high rpm (voltage) at low torque (current) output from the engine into a higher torque lower rpm drive for the wheels, with some loss due to friction (DCR) and parasitic losses from the helical cut gears (parasitic L and C). I often run all three output taps (4, 8, and 16 ohm) to a switch to purposely mismatch the load in a guitar amp. One could attempt to get a car moving in 3rd, or let the engine scream at the redline in 1st and still generate motion. This is not ideal in a car but can be useful in some circumstances. I used to run a certain popular autocross track entirely in second gear after the initial start in first, due to the time lost in shifting, my 7200 RPM redline, the need for both hands on the wheel, and the layout of the track (no long straight sections). It is however more useful in a guitar amp for a different "tone."
I assumed that my references to engine and wheels made my use of the word "transmission" somewhat obvious, but maybe that use is not so common outside the US. I see many references to DCT's (Dual Clutch Transmissions) in European automotive literature as that's where they were developed, so I assumed that the use was understood worldwide. In these cases, torque and RPM are "transformed" in the same manner as current and voltage is in the electrical case, and the power remains the same in the ideal case. The "gear ratio" (number of teeth on each gear) determines the transformation ratio in the same way the turns ratio does in a transformer. I have used this analogy to explain transformers to an automotive enthusiast, and to explain axle ratio and final drive ratio in his pickup truck to my boss, an electrical engineer.
Here in the US "transmission" also relates to the use of "transformers" to move electrical power from a power generation plant to the end users who are often a large distance away. It also is used to refer to a method of launching some Radio Frequency energy into free space via an antenna, often some audio or audio/video content is modulated onto that RF signal. Propagation of a communicable like Covid disease is another use. There are likely many others.
Here in the US "transmission" also relates to the use of "transformers" to move electrical power from a power generation plant to the end users who are often a large distance away. It also is used to refer to a method of launching some Radio Frequency energy into free space via an antenna, often some audio or audio/video content is modulated onto that RF signal. Propagation of a communicable like Covid disease is another use. There are likely many others.
The output tube modulates the DC through the primary creating a building and collapsing magnetic flux which is transfered to the secondary as a current that changes direction and voltage that changes polarity.
Do you mean there is an AC output signal from the valve which is superimposed on the constant DC voltage of its operating point? The transformer only transforms the AC signal; the DC is blocked.
For an audio output transformer the current through the primary is always DC. One way current that rises and falls. It is always one way with voltage that stays (+). The plate voltage never goes (-), so the current cannot change direction. The signal voltage is not Alternating Current.
I meant 'transmission' in the sense that, say for a tube amp, a high voltage low current swing is transformed to a low voltage high current swing, sort of in the manner of a mechanical transmission changing a high RPM low torque output into a low RPM high torque one. I was attempting to use that an an analogy to transformer action. Of course coupling and loss mechanisms are completely different in the two devices, so the analogy would not carry over to that very well at all.
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He knows way more than you do. Sorry you do not seem to grasp anything that people are telling you. You seriously are wearing out your welcome here.
Don't restrict your definition of DC to a static voltage. That's only for batteries or a regulated voltage that is fixed. DC is current that flows in one direction regardless of the amplitude. People have trouble visualizing the flux as it stops at the peak and although the voltage and current are still moving in one direction, but falling, the flux changes direction and that causes a change in current ''direction'' in the secondary.
So you are talking about say, a rectified AC voltage. That up & down motion of the rectified voltage is itself an AC signal, even if all of it is above or below the 0Vdc level. It's AC riding on a DC Offset voltage.
You need to seperate your concept of Acurrent from voltage. A true alternating voltage changes polarity. That creates ACurrent. The plate voltage is never alternating polarity, it is only modulated, single polarity derived from the B+. The grid signal shuts off the current or raises the current through the tube but it never changes direction. The plate voltage is just a result of the level of the current through the tube. MAX current is the point of low plate voltage and MINIMUM current allows the plate to stay high, but it all never changes direction. Alternating means change of polarity, not amplitude.
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No need to argue about basic definitions. The circuits are what they are, however you might choose to describe them.
All active devices in linear amplifiers have a quiescent DC operating point, from which the output signal varies.
Superposition in linear circuits allows you to describe a node voltage as a DC voltage summed with an AC voltage.
V(AC + DC) = V(AC) + V(DC)
And when you small signal analyze a linear circuit, the first thing you do is short all DC sources, and open all CC sources.
All active devices in linear amplifiers have a quiescent DC operating point, from which the output signal varies.
Superposition in linear circuits allows you to describe a node voltage as a DC voltage summed with an AC voltage.
V(AC + DC) = V(AC) + V(DC)
And when you small signal analyze a linear circuit, the first thing you do is short all DC sources, and open all CC sources.
MarekH just wanted to know how a transformer could pass DC to AC. We're working toward the goal understanding transformer action.
Interersting you use the word transmission to describe a process you call transforming. Intriguing 😎