Capacitors, Risistors and combing them

[hawk]

Hi, I am new to pedal building and have a couple questions.

When building a circuit and I find I don't have a 120ohm resistor handy will putting a 100ohm and a 20ohm in series in its place achieve that same effect?

Further to this can a 120nF capacitor be substituted with a 100nF and 20nF resistor (in parallel of course!)?

I understand the basic concepts of resistance and capacitance and how they add up in series and parallel but by splitting these up into two physical components am I changing any other characteristics of the circuit or will I encounter anything weird?

[micromegas]

at this frequency you can do that with no problem anywhere you want to. (I cannot find any situation in pedal building right now where combining passive components should be a problem..)

[HamSandwich]

^^^ in what scenarios would using two series resistors or two parallel caps (or their counterparts) not result in the desired resitance or capacitance?

[alanp]

Every part has a specified tolerance. For example, say we have a 100k resistor of 5% tolerance (carbon film.) This means that while the label says 100k, in practice the resistor can be anywhere from 95k to 105k and still be within spec.

Now, if you have two 5% 100k resistors in series, then the tolerances add up (or subtract.) So with two 100k 5% resistors in series, the total resistance can be anywhere from 190k to 210k. The finer tolerance'd the resistor, the less range you have to deal with. If you use two 1% 100k resistors in series, then the range is 198k to 202k (much less.)

Similar story with capacitors.

If you have nothing else on hand, but the value is pretty important, then check a few of each value with your DMM and pick the closest one to the spec'ed value.

[micromegas]

Every part has a specified tolerance. For example, say we have a 100k resistor of 5% tolerance (carbon film.) This means that while the label says 100k, in practice the resistor can be anywhere from 95k to 105k and still be within spec.

Now, if you have two 5% 100k resistors in series, then the tolerances add up (or subtract.) So with two 100k 5% resistors in series, the total resistance can be anywhere from 190k to 210k. The finer tolerance'd the resistor, the less range you have to deal with. If you use two 1% 100k resistors in series, then the range is 198k to 202k (much less.)

Similar story with capacitors.

If you have nothing else on hand, but the value is pretty important, then check a few of each value with your DMM and pick the closest one to the spec'ed value.

+1