[sdiy] 1 Meg input level pots?

[Neil Johnson]

James,

> Since I would be basically using them as voltage dividers, I have  
> to ask, what bad thing happens if I go ahead and throw caution to  
> the wind and use these things for input level control pots ?

If you're using them to mix signals into an inverting summing amp  
(most likely) then you really need about 10:1 ratio of input resistor  
to pot resistance, otherwise the input resistor loads the pot and you  
end up with a non-linear (log-like) response curve.

So with a 1M pot track you'd need an input resistor of at least 10M.   
Which is not very practical and will very likely introduce noise  
(both thermal and stray pickup, like a taxi radio) into your  
circuits.  Ok, there are ways to avoid this (e.g. in sample-hold  
amps), but they add complexity where you don't need it.

I did something like you did a while back, but went for 10k pots so  
that I could use 100k input resistors, which is a bit of a standard  
(although not cast in stone!).

Hope this helps in some way.

Neil
--
http://www.njohnson.co.uk