Rupert Neve Portico 5043 - Compressor / Limiter Duo - Manual (Page 7)

DESCRIPTION
6
THE CONTROL CHAIN:
FEED FORWARD or FEED BACK
If the V.C.A. Control voltage is taken from the 5043 input, (i.e. before the V.C.A.) the V.C.A.
"knows" right away that a gain change is required and there is almost immediate response. This is
known, logically, as a "Feed-Forward" compressor.
If the V.C.A. control voltage is taken from the 5043 output, (i.e. after the V.C.A.) it cannot act
immediately on the V.C.A. because it has already been modified by settings of the V.C.A. and
circuits through which it has passed. This is known as a "Feed-Back" compressor. The two
compression characteristics are quite different, there is more "overshoot" and both the attack and
recovery ramps are changed, providing the user with powerful choices.
A choice between "Feed-Forward" and "Feed-Back" circuitry is provided. Almost all Mr. Rupert
Neve's earlier designs were "Feed-Back". They were more musical and sweeter than with "Feed-
Forward" designs.
The way in which these modes change the dynamic performance can be seen in the above graph -
but the more interesting effects are noted by listening - "Feed-Back" produces a sweeter, warmer
sound but is not as accurate if you need to protect a transmitter, for example.
-20
+20
-18
-16
-14
-12
-10
-8
-6
-4
-2
-0
+2
+4
+6
+8
+10
+12
+14
+16
+18
dBu
-20 +20 -15 -10 -5 +0 +5 +10 +15
dBu
FeedBack Mode FeedFoward Mode