Re: Expression/Volume pedals

[SoundFNR@aol.com]

In a message dated 05/11/99 17:04:39 GMT Standard Time, 
kevin@minds-eye.org 
writes:

> What exactly
>  does a pedal need to work as an expression pedal (generally)?  Will any
>  volume pedal work (why, why not)?
Expression pedals and volume pedals both (usually) work by a mechanical 
action
which turns the spindle of a potentiometer (=pot)
pots come in a number of varieties, but most are either
linear or logarithmic
log. pots are used as volume controls for audio signals, most of the 
resistance is at the 'full on' end of scale which is supposed to compensate
for the way in which we perceive volume. We hear twice the energy
in an audio signal as being 'a step louder', roughly an anti-logarithmic 
response.

Using a linear pot as a volume control would mean the amount of audio 
energy
would be proportional to how far the pot was turned, so our ears would 
tell 
us 
that 'all all the volume is in the first half'.

Also many volume pedals, especially the older ones don't turn the pot 
through 
its
full range ( you have to turn up a the amp to compensate)   

An expression pedal wants an even sweep of voltage across the whole range,
hence a linear pot which must be swept through its entire range.

Hope that helps.                  (?)

Andy Butler
Lexicon Vortex Database (new section on foot devices)
http://members.aol.com/soundfnr/vortex.htm