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I need an (for audio bandwidth) all-pass filter that has 0 degrees shift in low frequency and +180 degrees shift at high frequency.

The ones here https://sound-au.com/articles/active-filters.htm (figure 7.5) do just the reverse. All-pass filters from Rod Elliot's site

Can somebody please post a schematic or link to an op-amp based implementation?

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  • \$\begingroup\$ Please include the schematic in your post so your readers don't have to follow a link to understand your question. Leave the link there to acknowledge the source. There's an edit link below your question. \$\endgroup\$ – Transistor Jun 12 '20 at 16:53
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    \$\begingroup\$ +180 at high frequencies is non-causal. If you really need to do this, you'll just have to run time backwards. (Consider if there's a way to approximate what you need with the classic all-pass you found and an inverter). \$\endgroup\$ – user_1818839 Jun 12 '20 at 16:53
  • \$\begingroup\$ @BrianDrummond It might not be the first time I meet someone meaning to say -180, instead of the +180. Maybe OP meant it negative? \$\endgroup\$ – a concerned citizen Jun 12 '20 at 21:25
  • \$\begingroup\$ @aconcernedcitizen if that were so, the linked solution would suit his purpose. \$\endgroup\$ – user_1818839 Jun 13 '20 at 10:18
  • \$\begingroup\$ @wonderfullot. I rejected your edit of my post as you were trying to start a conversation in my post. That's not how this site (or any other site I've ever seen) works. My post is now deleted. \$\endgroup\$ – Transistor Jun 13 '20 at 15:09

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