[sdiy] Another Newbie Question - Lin vs. Log Mixer modules

[Scott Bernardi]

The ear's response to volume levels is logarithmic in nature. That is,
doubling the amplitude of a signal is not perceived as a doubling in
volume, it takes much more. A "audio" or "log" taper potentiometer
approximates the response of a human ear when used as a voltage
divider/attenuator.  So you'll see log pots in circuits that set
amplitudes (volume).
Frequency is another parameter that we perceive in a non-linear (in this
case exponential, the inverse of logarithmic) fashion. So you might also
see log pots to set frequency in simple oscillators like LFO's.
A variation of the log pot is the reverse log taper. As you rotate the
wiper, a normal log taper pot will change resistance slowly at first and
faster as it gets. The reverse log taper does the opposite.  Q/resonance
controls

A tip: the way to tell if a pot is log taper: measure the resistance
between the center and both end taps when the wiper is set at mid
rotation. If the resistances are pretty much equal, it's a linear pot.
If not, it's log.
Other tricks: you can approximate a log taper with a linear pot used as
a voltage divider if you load it down with a resistance of about 1/10
the pot value. Eg, 100k lin pot with a 10k load.  See Chis List's handy
java applet that plots this at
http://www.mindspring.com/~clist/PotGraph.html.

"Rhen, Kris" wrote:

>
>
> Is the only difference typically lin vs. log pots?  Thanks
> KRIS
>
>
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--
Scott Bernardi
sbernardi at home.net