22K Log conductive plastic pot

Fri Mar 12, 2010 12:03 am   

I am looking for a UK source of a 22K or 25K log panel mounting
conductive plastic or cermet pot. I have checked Farnell, RS, Rapid and
Maplin to no avail.

Cheers

Ian

Fri Mar 12, 2010 12:26 am   

"Ian Bell" <


** Use one of these 50K dual linear pots:

http://uk.farnell.com/vishay-sfernice/p9a2r100fisx1503ma/pot-linear-dual-50k/dp/8791368?Ntt=8791368

Connect the two sections in tandem - ie, the wiper of the first goes to the
top of the second.

The law is then close to log.

10% = -40dB

25% = -24dB

50% = -12dB

70% = -3dB.



...... Phil

Fri Mar 12, 2010 10:57 am   

Phil Allison wrote:


Thanks for that Phil, it is something I had considered and it has the
advantage that the law is much more repeatable. Unfortunately I should
have been more specific about the application and in this case I need
the log(ish) law but it is not to be used as a potentiometer but as a
variable resistance (in an equaliser). As far as I can see, cascaded
linear pots do not give that - for example the total resistance from the
second wiper to ground at the 50% point is 10K. Is there some other way
of connecting a pair of linear pots to give an approximate log law
resistance between two terminals??

Ah, I just realised if I connect the second wiper to its upper terminal
I get 6.25K at the mid point - that might just do it.

Cheers

Ian