A mechanical volume control that actually works!

[John Doe]

Like most everyone else, I have had many devices that included a
mechanical rotary volume control. And as far as I can remember, on
every single device, the volume control eventually failed, usually
being the first problem. The symptom was always the same,
eventually the low level volume would completely drop out, so that
turning the volume up from zero would jump from zero to some low
or medium volume level.

Ten or fifteen years ago, I bought a namebrand pair of computer
speakers, 5 or 10 watts total. About five years ago, the main
speaker of the pair, the one with the volume and other controls on
it, began being used 24/7, with the volume adjusted regularly. Low
and behold, the mechanical volume control still works flawlessly.
I have used it probably 10 to 20 times more than any other volume
control I have ever had.

Assuming my experience is common... Are decent mechanical volume
controls expensive, or is it just that manufacturers go for the
very cheapest volume control?

[whit3rd]

On Nov 23, 12:31 pm, John Doe <j...@usenetlove.invalid> wrote:
> Like most everyone else, I have had many devices that included a
> mechanical rotary volume control. And as far as I can remember, on

> every single device, the volume control eventually failed...

>
> Assuming my experience is common... Are decent mechanical volume
> controls expensive, or is it just that manufacturers go for the
> very cheapest volume control?

Yes, to both. The cheapest potentiometers (volume controls)
are plated steel spring contacts onto carbon-paint resistive elements
on phenolic plastic substrates. They work quite well, but the
carbon is prone to oxidation and can be abraded; the plating on the
spring
can wear through or crack; the contact pressure can be uneven,
and scrape through the 'paint'. If contact pressure is too high, it
wears through the conductor. If it's too low, the contact may be
impaired by any bit of dust or dirt.

High-end controls use low-pressure-high-contact-area wipers (extra
parts here), on non-oxidizing conductive films with high strength,
sometimes
there's a sandwich of conductors with the top layer being a lubricant/
contact
enhancer ('conductive plastic' is typical). Really high-end controls
use
no moving parts at all, the knob is just an input to a digital
controller
that programs a variable-gain amplifier or multiplier.