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Old 25th August 2005, 07:44 PM   #1
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Default Programmable Active Crossover(analog)

I have designed a Software programmable active filter(analog) .The picture shows one channel of the finished circuit.
It is a 2-way Linkwitz-Riley configuration(24dB/oct).The devices shown on the blue sockets have 4 software adjustable potentiometers inside each one,by tying the wiper to one end of the pot you create an adjustable resistor.Different crossover points are achived by changing the resistor values(software controlled),256 discrete resistor values can be programmed(approx. 100hz crossover step resolution).

I am using a "Basic Stamp"microcontroller to program the resistor values.I am using the "I2C" protocol for communication with the digital pots.The quad pots are from Analog Devices(part number is AD5263).

It is my intention to further develop this project and have some PC boards made up in the near future.I will share the details for those who have an interest in this x-over.I do not have any formal documentation at this point,my main objective was to get the prototype built and get some initial data.

My initial bench tests of the prototype are very positive,It looks like the channel balance is within .2 db between the LP/HP sections at the programmed crossover point.

All comments are welcome.

Regards Bob C.
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Old 25th August 2005, 08:38 PM   #2
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Rob, I am definitely interested. I will be in touch! Very cool!
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Old 26th August 2005, 01:47 AM   #3
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I am also very, very interested.
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Old 28th August 2005, 06:04 PM   #4
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Very interesting
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Old 29th August 2005, 06:23 PM   #5
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Very neat

Maybe I should use these IC's for my monster filter with FDNR, see my sig below.
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Old 29th August 2005, 10:25 PM   #6
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Default Active Filter

PA: Your FDNR filter board could accomodate both techniques.The end user could have either a software programmable filter ,or by leaving out the digital pots and installing fixed value resistors,You have a conventional active filter. Bob C.
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Old 29th August 2005, 10:29 PM   #7
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Good work, let me know when you want to design the PCB -- Jack
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Old 30th August 2005, 05:31 PM   #8
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Hi Bob,

This is going to be really cool.

I am working on my PCB with the parts you mentioned. I am about 80% done I would say. The only issues left to resolve for me are the ones related to the PIC itself and human interface.

Cheers!
Russ
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Old 30th August 2005, 06:13 PM   #9
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How good do these digi pots sound? Or it doesn't matter?
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Old 30th August 2005, 07:10 PM   #10
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Well they should sound fine, the specs are good. Bob has actually heard them, so I will let him answer based on experience.

Cheers!
Russ
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