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In many circuits, where there is an oscillating sound source, and a loudspeaker (let us assume for simplicity that the signal is on a level that can power the speaker and no further amplification is needed), volume control is done by adding a potentiometer.

This is such simple, and primitive design task, that there is very little exact and detailed info on the internet how to implement such a thing.

I have seen two ways of doing this:

A: connecting the pot as a current divider.

B: connecting the pot as a "pot - a voltage divider.

I have two questions:

  1. Which one is correct? If both, when to use which one?

  2. (this is an even more dummy question) When the pot is set to zero (and volume is zero) there is a short - if even for just a very small period of time. Is it not problematic: that I am shorting the circuit with zero volume? -- I am talking about e.g. an atari punk console.

Remark to the second q.: heuristically, a 4 Ohm speaker is not musch different thrn shorting (4 Ohm is a very little resistance), but still.. this bothers me. Is it because of alternating current behaves differently? Can someone elaborate on this and make me reach enlightment?

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    \$\begingroup\$ Volume controls are almost never done between amplifier output and speaker, due to the currents being large, as speakers are usually quite heavy load. So the assumption is not good and it is extra difficult to make a volume adjustment on speaker level signals so that the potentiometer does not burn. \$\endgroup\$
    – Justme
    Aug 13, 2023 at 8:09
  • \$\begingroup\$ As a side note, whether any given resistance is a 'short' is heavily dependant on the situation/context. In a car at 12V, 4 ohms is only 3A/36W - that's about half of one headlamp. A starter motor drawing hundreds of amps is only going to be tens of milliohms. But for a higher-voltage lower-current supply, an extra load of even a few hundred ohms could be enough to cause a failure. \$\endgroup\$ Aug 13, 2023 at 10:30

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Usually a volume control comes before the final amplification. They are generally connected so that the full resistance of the pot is across the source and the output is take from the wiper. When set at zero the output will be shorted, but the source will see the full resistance, and it is the source that you don't want shorted, the pot is usually followed by the input of the power amplifier and this can be shorted, although usually not for DC. Depending on the circuit, DC blocking capacitors are usually used between the source and pot, and between the pot wiper and whatever it feeds, to keep the pot from affecting the bias of the amplifiers.

This is typical of how a volume pot is usually implemented:

schematic

simulate this circuit – Schematic created using CircuitLab

When using a pot between a power amplifier and speaker you would use what is known as an L-pad, this is a special pot that maintains a fixed impedance for the amplifier, usually 4, 8, or 16 ohms. They also need to be rated to handle the power output of the amplifier. For something with very low power such as a headphone amp, you might be able to get away with using a regular pot, but it has to be a relatively low resistance one.

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