How does a volume control work?

December 27, 2017
 by Paul McGowan

9 comments on “How does a volume control work?”

  1. Hi Paul,

    Thanks for the informative video. While I knew/know that the volume control (Pot) was a variable resister for many years, I too still think of the volume control as a gas pedal. Go figure.

    Related to this, it would be great if you could do a complimentary video on how a digital volume control works.

    Thanks and I love these little videos. Keep up the great work.

  2. Hi Paul,

    I also would like to understand how the volume control works in my Stellar Gain DAC. Is it possible to explain on a video (in layman’s terms) without letting the competition in on your secret to this achievement?

    Thanks
    Scott

    1. I would think that it is a variable gain amplifier. Instead of attenuating the signal, the volume control increases or decreases the amplifier gain which affects the output volume. My 2 cents.

      1. Yup. It’s called a Gilbert Cell or a Transconductance amplifier and it uses varying amounts of current to set the gain. The beauty of this scheme is regardless of the gain the performance of the amplifier is unchanged. Thus for any given level the sound will be the same. It’s used a lot in analog recording consoles.

  3. Years ago when I was accumulating parts to build a simple tube pre-amp an electrical engineer friend gave me lots of helpful advice.
    I recall him saying a volume control is like the nozzle on a garden hose which lets you vary the flow of water ( ie, current, depending the voltage pressure). I thought that was pretty good.

  4. Paul. I do feel that turning up the volume is a bit like pressing the gas pedal. You are increasing the signal level into your power amp. If it is the normal fixed gain class AB design, without signal it will be idling; drawing little current and (hopefully) making no sound. As the level of the input signal increases it draws more current and the output volume rises (as does the total distortion, although crossover distortion is largely volume independent and is thus more noticeable at low volume)

    1. You’re correct, Chris but you moved too far forward. Remember, I was focusing on the volume control and there it is brake relative to a gas pedal. Imagine that the best sounding pot is one that is turned at 100% – brakes off.

      Downstream all sorts of things happen but that wasn’t the point of my explanation.

      So yes, from a system perspective playing louder is like stepping on the gas. From the volume controls standpoint it is like stepping on the brakes. This distinction is important depending on circumstances. So, imagine a device with a volume control feeding another with a control (like a DAC feeding a preamp or a preamp feeding a power amp with gain controls). In this case it’s important to realize you want to keep the feeding control as high as possible.

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