The volume control in a hi-fi amp or preamp (or any other audio device, for that matter), is a truly simple concept, right? Wrong. In order to get a smooth increase in level, the potentiometer (pot) must be logarithmic to match the non-linear characteristics of our hearing. A linear pot used for volume is quite unsatisfactory.
Better Volume Control
Originally designed by Peter Baxandall (of feedback tone control fame, amongst many other designs), there is also an active version of the ‘Better Volume Control’, which uses an opamp and a pot in the feedback loop. The log law is almost identical to that for the passive design above, but it can provide gain as well as attenuation.
Better Balance Control
Bernd, a reader of The Audio Pages, has contributed a useful variation – in this case, a “better balance” control. Note that the configuration described requires a high impedance load, and the passive “Better Volume Control” cannot be used in this circuit.
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