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Active filter board GB
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Old 16th April 2017, 05:41 AM   #1361
adila is offline adila  Romania
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Default Active Crossover GB

Hi. Is there anybody else who is actually selling PCBs, please PM? It seems that are still much in demand. Thanks.
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Old 30th April 2017, 01:24 PM   #1362
adila is offline adila  Romania
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Default 2.1 Active Crossover

Hi all,

I decided to build my own crossover starting from the Active Filter Four project by Jens Rasmussen and Bob Ellis. This is my first project of this kind so please excuse me if I ask you stupid questions some time.

One PCB should accommodate two channels (stereo) and one sub-woofer common for both channels.

My first dilemma:

Do I need two LP filters and combine the signal before the output buffer or one LP filter can do both channels?

Here are some details about the OP-AMPs I intend to use:

- OPA1644 (14SOIC) for all the filter stages/sections. I will keep the original design with the selection jumpers between the 2nd order filters, just to have an idea about the differences between a 2nd order and a 4th order filter. I choose this OP-Amp because I may use only one to cover both 2nd order sections of a filter.

- OPA1602/2134 (8SOIC) for the input/output buffers. If you guys can recommend me one of them it will be nice, or I can try both to see the differences if any. I will use PCB adapters between 8SOIC and 8DIP.

Thanks,
Adrian

Last edited by adila; 30th April 2017 at 01:37 PM.
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Old 1st May 2017, 08:57 AM   #1363
AndrewT is offline AndrewT  Scotland
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you can sum the two channels to give a mono channel.
You can then filter that mono channel to give a low bass only channel for a 2.1 system.

There is a filter that allows summing at it's input. Use an MFB low pass filter, Add one extra input resistor for each extra channel you want to sum. Yes one opamp does summing and 2pole filtering on one tiny PCB space. The MFB filter is inverting topology. The output is thus 180degrees out of phase with the normal channels. Swap the speaker leads if you need to get that channel back into phaseat the crossover frequency.

If you want/need more poles to the low pass filter just add on another S&K stage.
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Old 30th March 2018, 09:27 PM   #1364
Henkjan is offline Henkjan  Netherlands
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I just got my hands on 4 or these boards. can someone point me to the build thread for these? I tried search, but cound't find it, but I see it mentioned in the posts in this topic... Thanks.
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Old 31st March 2018, 10:13 PM   #1365
BobEllis is offline BobEllis  United States
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PM me with your email and I will send you the manual.
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Old 14th February 2019, 01:43 AM   #1366
pixelpusher is online now pixelpusher  United States
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Default Power input connectors

I've been using these crossover boards for years and have always wondered about the power input geometry. There are three large holes in the PCB, two at the edge are voltage in and the one behind is ground. Surely these must have been designed for some sort of connector but I've not been able to find anything that fits. I just soldered wires to the holes which works OK but I really think something else was intended here. Anyone have any ideas? See the attached picture.

Thanks Much
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File Type: jpg AF4.jpg (230.5 KB, 112 views)
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Old 14th February 2019, 02:07 AM   #1367
BobEllis is offline BobEllis  United States
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We weren't so sophisticated back then. The multiple holes allowed for daisy chaining the boards to a single power supply.
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Old 14th February 2019, 03:40 AM   #1368
pixelpusher is online now pixelpusher  United States
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Thanks Bob,
Gad to know I'm not missing something.
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Old 24th April 2019, 05:11 PM   #1369
jernejc is offline jernejc  Slovenia
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Hello,
Is there any more of these pcb's available? I am interested for a pair of crossover filter.
Jernej
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