Volume pot "the wrong way round"

In some circuits I have noted that the wiper is the input, not the 'top' of the pot, why?

[ms660]

Sometimes there was only one way such as a pot used for a receiver's detector's load.

I've seen either way in record players, not sure why, someone will know.

Lawrence.

[G6Tanuki]

Originally Posted by merlinmaxwell

In some circuits I have noted that the wiper is the input, not the 'top' of the pot, why?

It can potentially (pun intended!) save a resistor.

How? By using the full length of the track as the base-to-ground resistor of the bias network, and feeding the signal in to the wiper.

Alternatively, the 'ends' of the pot can be the collector-load resistor of a transistor, with the wiper feeding the next stage through a capacitor in the usual way.

Either way, you come out with the resistor-count being reduced by 1, which pleases the production-accountant even if he doesn't understand issues like variable load-impedances.

[ukcol]

Originally Posted by G6Tanuki

It can potentially (pun intended!) save a resistor.

How? By using the full length of the track as the base-to-ground resistor of the bias network, and feeding the signal in to the wiper.

I think this is the answer except more usually applied to valve technology where the track is used as the (control) grid resistor.

[G8HQP Dave]

Bad idea, because pots tend to be less reliable than fixed resistors. However, it is the user who suffers the clicks and damaged valves caused by the grid resistor going open circuit so the manufacturer doesn't mind.

[ParcGwyn]

By using the full length of the track as the base-to-ground resistor of the bias network, and feeding the signal in to the wiper.

Wasn't this what George Dobbs in the Ladybird book?

Dave

GW7ONS