active filters: which resistors to buy

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I am about to buy a lot of resistors (3000+) for my active filters, and I was just wondering which values I should get. On linkwitzs site there are equations for hp, lp, notch and peak filters and I was wondering what range of resistor values would be optimal for me.

Would I get lower noise/distortion with lower resistors and higher caps or higher valued resistors and lower caps?

Is there a limit to how small or large of a resistor I can use?
 
Bill Fitzpatrick said:
What about it? For an electronic crossover, resistor noise isn't much of a factor.
Maybe so, but stray caps will have bigger influence if higher resistor values are used. I agree with Jens here, use 10-22 k max but beware of minimum values also for caps. The "opamp" or opamp may get increased distortion with heavy loads.
 
Well I will try to explain my point of view.

Active filters, pre amps, and other small signal carrying circuits will contribute relatively much to the overall noise in the signal chain.

Bigger value resistors are noisier than small value resistors. This fact along with the fact that small resistors require bigger capacitors than small ones to generate the same filter function, mean that the overall influence by parasitic capacitance will be smaller.

Anyway, the question was the range of resistors required to make active filters, I gave my view on the matter, it might be different than yours. After all we all have different experience with this, and mine tells me to try to keep the resistor values down.

\Jens
 
Active filter design

Hi:Your first step in designing your filter circuit is to determine your crossover frequencies.Step two is to pick a capacitor value and run some initial calculations to determine appropriate resistor values based on your capacitor value.It is far easier to adjust resistor values than it is to try to find an exact capacitor value to achieve your target crossover point.I would strive for a 1% tolerance on your capacitors,you can hand match 5% resistors if you have to keep the cost down.It is certainly true that larger values of resistors can increase noise levels in a circuit,most engineers will tell you this.I would encourage you to test your filter with a sweep generator and plot the response if possible.
Good luck...
 
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