*07 Mar 2012, 12:36 UTC*

(If you're not familiar with this kind of diagram, the triangles are scalers/attenuators i.e. multiply-by-constant, the plusses are adders, and the `z^-1`

boxes are 1-cycle delays.)

From the diagram:

```
h = x + ay
i = A' = h + bB
y = B' = fi + cA
= fh + fbB + cA
= fx + fay + fbB + cA
```

so

```
y = (fx + fbB + cA) / (1 - fa)
A' = h + bB
B' = y
```

In other words,

`y`

is unchanged from the filter without the delay-free loop, except for the factor`1/(1-fa)`

`A'`

and`B'`

must be calculated using the new`y`

, and using`h`

in place of`x`