Resistor + capacitor in parallel - figuring out the amount of high-pass "boost"?

[midwayfair]

So if I have a resistor and capacitor in parallel to create a high-pass filter, like this:
                --C1--
previous---|       |-------following stage
                --R1--    |
                           R2
                             |
                           Ground


Is this as simple as figuring out the gain reduction of R1/R2, then the frequency cutoff of C1 + R2, and then the amount of "boost" from C1 is whatever the gain reduction would have been?

So if, say, R1 = 100K, R2 = 1M, and C1 = 100pF. Everything above ~2K is boosted by 10%?

[tca]

So if, say, R1 = 100K, R2 = 1M, and C1 = 100pF. Everything above ~2K is boosted by 10%?

Boosted?!?

Assuming no current flows at the output, i. e., the same current flows trough Z1=C1||R1 and R2.

For f>>1/(2 pi C1 R1), 1/(2 pi C1 R2) => Vo/Vi~1.

For f<<1/(2 pi C1 R1) => Vo/Vi~R2/(R1+R2).

f1=1/(2 pi C1 R1), and with your values that gives fc~16kHz.
f2=1/(2 pi C1 R2), and with your values that gives fc~1.6kHz.

P.S.
If you think of it as non-atenuation, that is a "boost," then the higher frequencies will have a boost, relatively to the bass, of 1+R2/R1=11.

P.P.S.
For the other cases, non-limiting frequency regimes, you have to work out the math.

[R.G.]

So if I have a resistor and capacitor in parallel to create a high-pass filter, like this:
                --C1--
previous---|       |-------following stage
                --R1--    |
                           R2
                             |
                           Ground


Is this as simple as figuring out the gain reduction of R1/R2, then the frequency cutoff of C1 + R2, and then the amount of "boost" from C1 is whatever the gain reduction would have been?

So if, say, R1 = 100K, R2 = 1M, and C1 = 100pF. Everything above ~2K is boosted by 10%?

[R.G.]

So if I have a resistor and capacitor in parallel to create a high-pass filter, like this:
                --C1--
previous---|       |-------following stage
                --R1--    |
                           R2
                             |
                           Ground


Is this as simple as figuring out the gain reduction of R1/R2, then the frequency cutoff of C1 + R2, and then the amount of "boost" from C1 is whatever the gain reduction would have been?

You can't tell without knowing the values of the "invisible components" - the internal impedance of the source driving it and the loading of the load it feeds.

A simple way to estimate for the special cases where the source driving impedance is very low compared to either R1 or R2, and where the loading of the input of the following stage is very high compared to R2 is this:

For frequencies low enough that the impedance of C1 is very high compared to R1, you have a simple voltage divider, and the output voltage loss is simply R2/(R1+R2). For frequencies high enough that the impedance of C1 is small compared to BOTH R1 and R2, the output has essentially no loss. For frequencies in the middle, where the impedance of C1 matters, and where there is no clear distinction between the impedances of C1, R1, and R2 (that is, none of them are more than 10:1 greater or less than) then you have to do the math.

[midwayfair]

So if, say, R1 = 100K, R2 = 1M, and C1 = 100pF. Everything above ~2K is boosted by 10%?

If you think of it as non-atenuation, that is a "boost," then the higher frequencies will have a boost, relatively to the bass, of 1+R2/R1=11.

Well, that is why I put "boosted" in quotation marks. I know it's a passive network.

[seedlings]

www.ampbooks.com/home/amplifier-calculators/bright-boost/
-and-
www.ampbooks.com/home/amplifier-calculators/coupling-capacitor/

Should give you a good idea with caps, resistor (volume), and in/out impedances.

CHAD