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Audio Precision option filter AWT
Audio Precision option filter AWT
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Old 21st September 2019, 07:12 AM   #1
IVX is offline IVX  Ukraine
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Location: south of China
Default Audio Precision option filter AWT

Hi there, I just bought AP sys-2522(pretty much the same thing as 2722 but older) and found there is no A-weighting filter option at all. Official AP in China asked $220+VAT for that board but I found System-1 AWT board docs here Cranial Crumbs: Audio Precision System One A-weighting filter
I've ordered PCB 59x50mm(as I measured PCBA from the pictures), polyprop caps were replaced for C0G SMD pairs for a fine adjustment, resistors are splitted to pairs as well for the same reason. OPA1612 instead of lf353 seems not necessary to, I just had good opamp and use it. ID resistors for auto-recognition were wrongly specified on the blogspot article, 23k/23k recognized as a 20kHz LPF. After I changed them for 270k/270k analyzer see my AWT "officially" and near for free
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Old 21st September 2019, 08:10 AM   #2
jan.didden is online now jan.didden  Europe
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Location: Westende Resort, BE coast
Well done! You see them sometimes on eBay as well, but your solution is very good.

Also thanks for the ID info, I wasn't aware how that worked. Is there somewhere an overview of the various codes for the many filters that exists?

BTW, if your unit has DSP and/or dual domain, there's also an AWG filter in the DSP I believe.

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Old 22nd September 2019, 10:35 PM   #3
Audio1Man is offline Audio1Man  United States
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The first AP FILTERS did not have ID RESISTORS. The ID RESISTORS show up the type of filters installed on the filter panel. No ID then only the slot #
Any of the filters can be used is System 1, 2, Cascade or 2700 family. The System One has EXTERNAL BNC IN and OUT on the front panel, while the System Two and up has 7 filter slots. They offered a new rear panel assembly with BNC IN and OUT cables and board connector so you could use your own filter.
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