Pots With 'Off' switch

[nugget]

Hi

I'm looking for a 250k linear pot with an off switch at the end of the travel (not a push pull) You know the sort of things some older radios had where the volume knob switched the radio off. All I can find on internet is dimmer light switches which arent right.

Can anyone point me in the right direction

Ta
Dave

[ikay]

I think what you're after is a rotary potentiometer switch. Farnell Electronics has a 220k lin version:

http://uk.farnell.com/jsp/displayProduct.jsp?sku=1637187&CMP=e-2072-00001000&gross_price=true

[mart]

I think the Fender "No load" tone pot will do what you want. Axesrus have them on their site, although they seem to be out of stock atm. Look here [url="http://www.axesrus.com/axeElectronicsPots.htm#CTS"]http://www.axesrus.c...icsPots.htm#CTS[/url] and scroll down for the Fender stuff.

Edited February 15, 2012 by mart

[icastle]

You're going to struggle with 250KΩ.

Nearest I can find is a 220KΩ one from Maplin, use one of those and stick 3x 10KΩ resistors in line with it if the value is critical?

[url="http://www.maplin.co.uk/standard-potentiometers-with-switch-2208"]http://www.maplin.co.uk/standard-potentiometers-with-switch-2208[/url]

[LawrenceH]

[quote name='icastle' timestamp='1329321459' post='1540630']
You're going to struggle with 250KΩ.

Nearest I can find is a 220KΩ one from Maplin, use one of those and stick 3x 10KΩ resistors in line with it if the value is critical?

[url="http://www.maplin.co.uk/standard-potentiometers-with-switch-2208"]http://www.maplin.co...ith-switch-2208[/url]
[/quote]

Or if the tolerances aren't really tight buy a load and measure each manually - find one about 10% over and you're there! Those Maplin ones are linear though so still may not be suitable

[nugget]

Thanks - I was looking on Farnell last night and missed those,

Gonna get some on order and have a play with tone pot bypass etc

Ta
Dave

[icastle]

[quote name='LawrenceH' timestamp='1329323582' post='1540676']
Or if the tolerances aren't really tight buy a load and measure each manually - find one about 10% over and you're there! Those Maplin ones are linear though so still may not be suitable
[/quote]

The OP did actually state that he was looking for linear...

[LawrenceH]

[quote name='icastle' timestamp='1329325174' post='1540712']
The OP did actually state that he was looking for linear...
[/quote]
So he did! That'll teach me to skim-read at work more carefully in future

[Davebassics]

Interesting idea. Forgive my ignorance but what are the benefits of having no load tone pot?

As far as I am aware a tone pot set to "full" passes everything up and over 20kHz. Removing the load wouldn't make a difference to the output signal as the impedances preamp inputs are usually set between 1 and 10M.


Am I missing something?

[ikay]

[quote name='Davebassics' timestamp='1329340606' post='1541056']
Am I missing something?
[/quote]

Apparently removing the cap completely does result in a subtly brighter tone, here's a demo (on guitar)

http://www.youtube.com/watch?v=dN3SlH-cEAg

[Davebassics]

Fair enough. There is a tiny but noticeable difference.