5/2002 - Jens Moller -
Introduction to Op-Amps - Part 5
Active Cross-Over Network
Please be aware that this discussion is aimed at the Pro-Audio
area, and is not intended for Audiophiles or other areas of circuit design outside
of the Pro-Audio environment. The concepts are generally the same, if not identical.
However the topic area is vast and the intent of this discussion is quick and effective
practical usage - not theory, advanced or extremely high end systems.
Adding an Active Cross-Over Network Circuit
Sometimes you want to Bi-Amp your system (ie. a seperate Power Amp for the Mids/Highs and
one for the Bass/Lows), or when you are recording, you simply want to split off the 2
frequency ranges (this is handy, since you rarely want to add much Reverb to Bass, where
you might want some on the Mids/Highs).
(The same function but at 4000 Hz)
And it will have a frequency response that matches the following curves:
Sample Passive input Stage to Active Cross-Over
If you don't need anything fancy, you only need to add a few components in order to
allow you to use the Active Cross-Over by itself (ie. you already have a Mixer that
you want to conect this to). Add the following as the input, and you are done:
It will operate in this fashion:
Sample 2 channel Mixer Stage that Drives Active Cross-Over
NOTE: The Level Control (seperate Volume Control) variable
resistors should be Audio Taper (Log taper), however Linear taper will work if thats all
you have available.
If you want to add the Active Cross-Over to an existing Mixer, or if you are building your
own Mixer, it would be added as part of the circuit, being driven off of the output
of the Op-Amp in the Final Mixer stage, like:
It could operate in this fashion:
See Part 4 - Active Tone Controls if you would like to see
how to add Tone Controls to this type of design.
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