[sdiy] Bournes 300K pots...

Jim Patchell patchell at silcom.com
Thu Jun 6 19:00:57 CEST 2002


    Yes, there is validity to your concern.  I am using the pots in a
sequencer...so, no problem.  The input impeadence is in the 10's of megohms.
For things like frequency controls on VCO's and the like...yeah, they are not
really suitable.  I will have to stick with the lower quality pots for now.

    -Jim

Neil Johnson wrote:

> Mmmmm...
>
> > about the "300K Bournes Pots" from electronic gold mine
>
> The URL for the click-happy is:
>
>      http://sales.goldmine-elec.com/prodinfo.asp?prodid=4198
>
> $  1.00 for a pack of 2 (50.0c each)
> $ 35.00 for 100         (35.0c each)
> $299.00 for 1,000       (29.9c each)
>
> Ok, the only trouble I have here is that, to prevent loading the
> potentiometer, the wiper load resistance needs to be at least 10 times the
> track resistance.  In this case, you're looking at a 3 Meg input (3M3
> NPV), which means adding a buffer amp to each pot.  Yikes!  I certainly
> wouldn't build a mixer with these pots.
>
> Maybe for a sequencer this is fine -- I suspect that each pot wiper would
> go to an analogue switch then to a high-Z buffer of some sort.
>
> Is it just me, or is there some validity to my concern?  Generally, I work
> with 100k input resistance, and 10k pots.
>
> Cheers,
> Neil
>
> --
> Neil Johnson :: Computer Laboratory :: University of Cambridge ::
> http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
> ----  IEE Cambridge Branch: http://www.iee-cambridge.org.uk  ----




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