Pot size?

[caspercody]

Is it better to put a bigger resistance size pot in when you cant find the exact size required? Example: if a circuit calls for a 2.5k pot, and all you have are a 2k and a 5k pot would it be wiser to use the 5k?

[jacobyjd]

Go bigger, then adjust the pot's range w/ resistors. In your case, you could place a 2.5k resistor across the outside lugs of the 5k lin pot and you're left with a 2.5k rev log pot. Not perfect, but it'll work

[caspercody]

So by using half the value on each side, this will cause the voltage to drop. Trying to remember electronics class, but that was 20 years ago.

But, would using a bigger pot, by itself, cause a big sound change?

[jacobyjd]

It is completely dependent on the circuit/application.

[liddokun]

Josh, I think you may have miscalculated there....a 2.5k resistor in parallel with a 5k pot would give you a 1.6k pot, correct me if I'm wrong.
1/RT=1/R1+1/R2...etc.


So wouldn't it be a 5k resistor across the two outside lugs of a 5k pot would give you 2.5k pot.

But anyways, I may be wrong, but in general when I can't find the right pot size, I opt for a bigger pot size and do a little calculating with the above formula to find a resistor I can add parallel to the pot to give me a closer value. Given, the taper will probably be thrown off, but I'd rather have the correct value pot than the correct value taper.

[jacobyjd]

Josh, I think you may have miscalculated there....a 2.5k resistor in parallel with a 5k pot would give you a 1.6k pot, correct me if I'm wrong.
1/RT=1/R1+1/R2...etc.


So wouldn't it be a 5k resistor across the two outside lugs of a 5k pot would give you 2.5k pot.

But anyways, I may be wrong, but in general when I can't find the right pot size, I opt for a bigger pot size and do a little calculating with the above formula to find a resistor I can add parallel to the pot to give me a closer value. Given, the taper will probably be thrown off, but I'd rather have the correct value pot than the correct value taper.

Ahh--sorry, you're absolutely right! I'm a little loopy today. a 5k resistor is what you'd want if the called-for pot value is 2.5.

However, Nam has it right for when you need to make a larger pot work in a pinch, even if it's not exactly twice the value of what's called-for. Just do some calculation to get you in the ballpark.

Here's the deal: use what you've got just to get it working. If that means using a 500k pot in place of a 100k, go for it--I generally tend to go higher. Lower is ok too, but you won't hear the full range of adjustment.

However, I'd keep this kind of thing to the breadboard or prototype, since you don't want to go to the trouble of boxing up a circuit only to make a replacement once you have the right part.

I'll use just about anything on my breadboard as long as it works...just make sure you note the concessions and limitations you make when it comes time to test the effect

[liddokun]

Well, if you have a pot and want it at half the resistance, you put a resistor of the same value in parallel. Anything else and you'd need to do the math.

But at any rate, I always find it's easier to take things away from something too big than it is to make something too small bigger.

[caspercody]

Thanks!! Coming back to me, resistors in series add up. In parallel it is the formula. And it is the opposite for capacitors.

Thanks again for the information.

[liddokun]

No problem. Happy building.