How to form high pass filter in preamp?

Fritz · 20th December 2003, 01:20 AM

Id like to build a 100HZ high pass filter into a preamp to compliment a lowpass filter for a subwoofer. Im attaching the passive components at one pair of the preamp outs. My question is:
What load impedance do I use to calculate the required filter capacitance? If the filter were before the driver Id use the speaker impedance at my desired crossover point. Since the filter will see the amplifier input as the load I have no idea whether I calculate the filter the same way. If so it seems the impendance may be 24k versus 6 or so for a speaker and that Ill get some odd numbers.

sreten · 20th December 2003, 11:53 AM

One way of doing it is changing the input coupling capacitor
of the power amplifier, in this case you use the input resistor
value to calculate the capacitance.

sreten.

Fritz · 20th December 2003, 03:56 PM

Thanks Sreten Ill give that a try

20th December 2003, 01:20 AM	#1
Fritz diyAudio Member Join Date: Aug 2002 Location: CA USA	How to form high pass filter in preamp? Id like to build a 100HZ high pass filter into a preamp to compliment a lowpass filter for a subwoofer. Im attaching the passive components at one pair of the preamp outs. My question is: What load impedance do I use to calculate the required filter capacitance? If the filter were before the driver Id use the speaker impedance at my desired crossover point. Since the filter will see the amplifier input as the load I have no idea whether I calculate the filter the same way. If so it seems the impendance may be 24k versus 6 or so for a speaker and that Ill get some odd numbers.

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20th December 2003, 11:53 AM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	One way of doing it is changing the input coupling capacitor of the power amplifier, in this case you use the input resistor value to calculate the capacitance. sreten.

20th December 2003, 03:56 PM	#3
Fritz diyAudio Member Join Date: Aug 2002 Location: CA USA	Thanks Sreten Ill give that a try