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Old 9th June 2012, 07:48 PM   #1
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Default How to control 10 pots in active cross?

Hello

I want to change cutoff frequency in my active cross externally..
so i have to control 10 pots together....

which is the easiest way to do that?

1)10 gang pot?and where?
2)do i have to go digitally?
3)10 trimmers on the same shaft?

i want your opinion about this...
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Old 10th June 2012, 08:52 AM   #2
2quad is offline 2quad  Norway
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There are a number of ways to do this. Using digital controlled analog is perhaps the best solution, such as digital controlled resistors or MDAC's.

But I would question the purpose of such a filter. I assume you are not satisfied with your current xover frequency and want to experiment to find the optimum. And when you have found this frequency, the need for adjustable xover is no longer there.

I would suggest that you buy/borrow a digital xover, find the optimum frequency and modify your current xover for that frequency.
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Old 10th June 2012, 07:15 PM   #3
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ok thanks for the rerply
its a way for me to find any optimum frequency for any speaker system so i want ot do it like this....change xo frequency externally...

anybody else has tried something like this?
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Old 10th June 2012, 07:41 PM   #4
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I suspect a good solution for this is likely to cost much more than just buying a DCX2496.
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Old 11th June 2012, 06:30 AM   #5
Calvin is online now Calvin  Germany
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Hi,

IŽd also suggest a digital filter (IIR) for the first shots. If YouŽve found a optimum configuration You may build a analog filter after that fashion.
If I had to control 10 pots at the same , IŽd think about two ways:
1) use digital Pots, controlled by a microcontroller. But similar to analog pots this is not exact since the pots vary quite alot in end-value.
2) useage of jumpers, DIP-sockets, or DIP-switches to modify the filter resistors. This may be ighly precise, but requires increased effort in complexity, parts number count and cost.
I tend to say that an analog filter only makes sense nowadays if it requires only a few simple filter structures and if it is not implemented using OP-amps.
If those requirements are not fulfilled a digital X-over is probabely superior an any way.

jauu
Calvin
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Old 18th June 2012, 04:26 AM   #6
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Older models of Krohn Hite filter had 4 single pots driven by gears coupled to the gear fitted on the drive shaft.

Gajanan Phadte
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Old 18th June 2012, 01:43 PM   #7
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I would say the easiest way would be to use a bunch of digital since they cost about the same as a regular pot any more,sometimes cheaper.

Or you can use something like this circuit to control more than one variable resistance opto-isolators,

Use a photoelectric-FET optocoupler as a linear voltage-controlled potentiometer | EDN

I had many sleepless nights for many many years thinking about this for a particular application similar to yours.
Even though this is not my circuit it is something along the lines that I was thinking about, since at the time digital pots where quite costly and hard to get back then.

I was building VCA's that had better performance than the opamp types using devices like these in the early 80's and late 70's.

jer

Last edited by geraldfryjr; 18th June 2012 at 01:45 PM.
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Old 25th June 2012, 10:48 PM   #8
dangus is offline dangus  Canada
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Some pro audio active crossovers used VCAs (voltage controlled amplifiers) to replace the pots that determined the tuning frequency. You may still be able to get the Analog Devices SSM2164 (quad low-cost VCA). Or there's the better SSM2018 which is still available to buy from Digikey - but it's a single VCA and over $7 each.

I believe it's also possible to use multiplying DAC chips as digital gain controls. Parallel the digital inputs and drive them with dipswitches or thumbwheel switches, so no microcontroller is involved (and there's no possibility of noise from digital activity).

Last edited by dangus; 25th June 2012 at 11:11 PM.
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Old 25th June 2012, 11:09 PM   #9
Pano is offline Pano  United States
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Get a digital crossover. DCX2496 or a miniDSP. Otherwise you'll spend all your time chasing bug and not crossover slopes.
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Old 25th June 2012, 11:36 PM   #10
wayne is offline wayne  United States
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Try Maxim DS1802 digital pot. Micro or push button interface. It has limited swing but may do the job. They have other options available also.
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