Modular Active Filter Idea (FilterBlocks) - diyAudio
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Old 24th April 2009, 08:46 PM   #1
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Default Modular Active Filter Idea (FilterBlocks)

Ok, wild idea (sort of). I'm sure many of you are going to read this and think either: a) "that's a dumb idea and it won't work because...." or b) "that's a great idea, but who is going to implement it?". Well, maybe you're right, but I think it's an excellent idea and I want to go ahead and throw it out there to get some feedback and maybe spark some interest.

Would it be possible to take the discrete functional circuits (input buffer, 12db/oct slope filter, Linkwitz Transform, notch/peak, etc.) combined in the "Active Filter 4 " and implement them independently on small, uniform sized PCBs? Then added headers at both ends of them (examples below) to allow them to be "plugged" into each other and pass the signal and supply voltage between each other. This way you could configure as many of them as you like in what ever order you like. The PCBs would connect horizontally and not stack vertically. A PCB could be created that routes the traces in the shape of a "C" so that the direction of the PCB flow could be "wrapped" and you wouldn't end up with one huge line of PCBs. They would function like active filter "legos" that could be combined in an endless number of combinations. Also, it would be much easier to make changes to your filter. Want to add a notch filter? Just plug it in... Get the picture? Thoughts? Anyone want to design the boards and do a GB? =)



Molex 90121-0125

Sullins PPPC051LGBN-RC


Obviously you would still have to calculate the values for each individual filter board to make the filter you desire. Hopefully the small boards would be fairly inexpensive so it would be easy to build a few and then swap them out to mix and match to preference. So, build a couple notch filters with different Q's and swap them to see what they sound like. If you end up with extra filter blocks you could use them in another project or possibly, if enough people are using them, trade with other people.
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Old 24th April 2009, 09:11 PM   #2
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I have had similar ideas.

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Old 25th April 2009, 01:30 AM   #3
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Dave:

Having confirmation from a proven thinker like yourself is encouraging! Did they ever amount to anything tangible?
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Old 25th April 2009, 04:41 AM   #4
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W, your idea will work fine if you implement it properly. For example, I would have some small local decoupling PS caps on each board, and would prefer if all the earths returned directly to a single point.

I have a pro active xover that uses a large PCB that contains power tracks and paths for the audio, but the SK24 filter stages are all on small daughter PCBs connected via SILs. Frequency is changed by component substitution with the Rs and Cs on small stand offs to allow easy soldering access.
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Old 26th April 2009, 01:35 PM   #5
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Ok, maybe a different question. Who would purchase something like this?
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Old 26th April 2009, 01:47 PM   #6
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Quote:
Originally posted by wigginjs
Who would purchase something like this?

I purchased something like this.

Cheaper, more versatile and probably better.
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Old 26th April 2009, 07:08 PM   #7
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Quote:
Originally posted by wigginjs
Ok, maybe a different question. Who would purchase something like this?
Purchase what? The pro unit I mentioned or something you're interested in making and selling?

The pro unit would be maybe 15 years old.

I can't be bothered any more, so I bought a few DCX 2496 instead.
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Old 26th April 2009, 09:29 PM   #8
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Aww... DCX2496?!

I don't know. Something about me doesn't like the extra D->A A->D conversion and also, how do you control the volume? Don't you need a 6 channel attenuator after the DCX?
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Old 26th April 2009, 09:33 PM   #9
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Quote:
Originally posted by wigginjs
how do you control the volume? Don't you need a 6 channel attenuator after the DCX?

Control the volume before the DCX.
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Old 26th April 2009, 09:43 PM   #10
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I think its a good idea - right now I use my computer to do what the DCX does, but when I have the design finalized, I'll do an analog equivalent of it. I guess I would rather have a few more opamps in the signal path than an extra A > D > A.

Go for it.

Also, its possible to do several different filters around one opamp, which is how I'll do it.
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