Cupcake - 82k

[camsna]

So. Mammoth Electronics usually rocks my world, but they sent me 8.2k resistors instead of 82k. I have a BUNCH of other values hanging around, just not 82k. So, my question is:

What is safe to sub in the place of R2? I have 100k and 68k. Or can I combine resistors to get close? I really need to get this one done and feel dead in the water without those 82k resistors.

What to do?!

[jkokura]

Do you have the ability to socket? If so, try both out and see which one works better.

Another alternative - are you up for some interesting ideas? Resistors are cumulative parts, meaning that when you place two resistors in series you get an addition thing going on. So, you can get to 82k by using a 68k and a 14k, or thereabouts. So if you have a 68k and a 12k or 15k you can get there. The math is a little bit crazy cause there's so many options.

Also, you can get strange things happening by having resistors in parallel. Check out this calculator I just googled. http://www.sengpielaudio.com/calculator-paralresist.htm

According to that, if you put a 150k and a 180k resistor in parallel, you get 81.818181818181...k resistance.

So you can get there three ways: Put two resistors in series, put two resistors in parallel, use one of the other options in your hands and see what happens.

Jacob

[camsna]

I've got 68s and 15s. 83k is close enough for comfort

[stecykmi]

Just for reference, the formula for resistors in parallel is [ (1 / R1) + (1 / R2) ] ^ -1

The result is that you can only decrease the equivalent value of resistors in parallel, which makes sense if you think about resistors as a channel for current to flow. It also means that if you have one resistor that is much larger than the other such that R1 >> R2, then the equivalent resistance is about R2. Another important special case is if R1 = R2, which produces a resistance of (0.5)R1, half the resistance.

strangely, the above formula is valid for capacitors in _series_, which is useful to know if you ever need to make cap substitutions.

and even though they're not really used much in effects pedals outside of wah pedals, but inductors use the same formulas as resistors.