[sdiy] Different pole notches and phasers

[Tom Wiltshire]

Hi all,

Could someone explain something I don’t understand clearly to me?

What does it mean to talk about the number of poles when discussing a notch filter?

Additionally, what’s the difference between a notch filter and a notch created with an allpass filter and the input added together? Is there a difference?

It seems to me there is, since multiple stages of allpass filters with the input added together (a phaser) creates multiple notches, whereas a multi-pole notch would just be a deeper/narrower notch. Is that right? Or could a 4-pole notch filter have two notches?

There’s something I don’t quite get here, and I’m struggling to find exactly what it is, hence the rather confused questions. Any clarification anyone can offer would be greatly appreciated.

Thanks,
Tom
 
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       Electric Druid
Synth & Stompbox DIY
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