SV: Re: [sdiy] Nonlinearities in IR3109 filters

[Sean Costello]

All digital filters use delay in the feedback part. Not by choice, but by
the nature of discrete time systems:

onePole1Input = input+feedback;
...bunch of operations...
feedback = OnePole4Output; // computed last, as it is the output of the
filter

The feedback can't be added back into the system until it has been computed,
which means that you have a delay in the feedback loop. Filters with
zero-delay feedback loops are not realizable, which is why digital
translations of analog filters are not trivial to do.

Sean Costello
----- Original Message ----- 
From: "karl dalen" <dalenkarl at yahoo.se>

> Really?
> Who uses delay in feedback part?
> Hmm, how does that actually sound, could be worth a try!?