coupling capacitor.

in the isd1100 spec sheet it recomends a coupling cap between the output and the input of the amp. my question is, will this filter out any of the frequncies? i know a high pass filter uses a cap and a resistor. and being that this doesn't have a resistor i don't know if it will act as a filter. my next question is, how do you calculate the size of the capacitor?

As a first approximation you compute the capacitative reactance over the frequency range of interest.
What you want is a reactance that is small with respect to the input impedance of the next stage over the frequency range of interest.

so Xc = the input impedance of the amp? and would you use the highest frequency you plan on passing or the lowest?

oh i see, Xc needs to be small in comparison to the input impedance.

The frequency where the Xc equals the input impedance is the cutoff frequency. The level at that frequency is attenuated by 0.707 times which is 3dB, half power, a small drop. For a highpass filter, lower frequencies are attenuated more at the rate of 6dB (half the level) per octave. The response is flat at about 5 times the cutoff frequency.