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As anyone knows, who has used one, a pot can become
noisy (scratchy). This noise exists in nearly all pots that have
been unused for a period of time, including those fresh from the
manufacturer. When a potentiometer has passed its useful life, this
noise can be a result of worn and dried out resistance elements.
But, long before, this point has been reached, the unit may appear
to be beyond recall because of noise caused by high contact resistance.
Before you decide to replace the pot, the pedal should
be connected to instrument and amplifier and put through its full
travel a number of times -- even up to 50 times or more. This will
often restore quiet operation. This procedure will sometimes be
required when trying out a pedal in a store.
The fact that a pedal is scratchy when first tried,
does not mean it is defective, providing it can be rectified as
described. Incidentally, no lubricant or other material should be
applied to any part of a potentiometer. To do so, will cause deterioration
of internal parts.
The resistance value preferred by most pedal users
is 500K Ohms (.5 MegOhms). Pots with this resistance value are more
subject to noise than those of 250K Ohms (.25 MegOhms), Other noise
that can exist in a pot is mechanical noise. This can be in the
form of a squeak, a click, or just the sound of 2 surfaces, the
wiper and the resistance element, rubbing together.
Manufacturers of potentiometers consider their use
in volume pedals to be a misapplication. Consequently, they must
be carefully selected and those having abnormal electrical or mechanical
noise should be rejected or discarded at the pedal-manufacturing
level. Other reasons for a particular pot being unsuitable for this
use are: poor taper, steps in the taper, and "hot spots." However,
if all these possible faults are avoided, a properly constructed
pot volume pedal will give excellent results, perform quietly, and
will operate a long time before pot replacement is required.
*Goodrich
Sound Company
8733 Silver Creek Road
Whitehall, Michigan 49461 USA
(231) 893-5702
Footnote by John Fabian of Carter Steel Guitars:
While you will encounter less noise with a lower resistance pot,
you must use a buffer amp between the guitar and volume pedal and
between the volume pedal and the amplifier in order to transfer
the full frequency range from the guitar to the amplifier . Volume
pedals which use low resistance pots (such as 10K Ohms) are "active"
pedals . They have the necessary buffer circuitry built inside.
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