User Manual
16
COMP IN
The compressor section is not bypassed with this button in. This may be the most useful control on the
compressor because it is there for “condence checks”. In particular, exercise it in both the quietest
and the loudest sections of the song. Watch out for the compressor exaggerating noise and room sound
in the quiet sections and chopping off transients and consonants in the loud sections, either of which
suggest maybe too much compressor “action”. Conversely, losing quiet phrases or inadvertent clipping
might suggest that a little more compression is warranted keeping in mind that you can always do a bit
more in the mix but un-doing over-compression is not fun and often not even possible.
FF/FB
These are two very different compressor modes, FEED BACK and FEED FORWARD. Vintage compressors
almost always were FEED BACK designs which means they looked at the output after the VCA (Voltage
Controlled Amplier) or gain changing element and used that signal to control the attenuation. FEED
FORWARD compressors became popular in the 80’s and read the signal before the VCA and through
more elaborate electronics to control the attenuation because this has some advantages in regards to
the ratio and control timing. Perhaps a more useful generalization is that the FB mode (button in) tends
to sound smoother and often more natural and tends to be quicker to set up. The FF mode can be more
useful for shaping the envelope of the sound and introducing more bounce and pumping in time with
the song, when that is the goal. FF compressors were often used on 80’s dance tracks. Some engineers
prefer FB with lower ratios and FF with higher ratios.
GAIN
Often referred to as Make Up Gain. Considering the compressor’s VCA is generally being forced to
attenuate louder signals some method of returning the average level to a volume comparable with the
compressor bypassed is desirable. The GAIN control is mostly used for this purpose especially for those
of us that depend on comparing compression to bypass. GAIN is often pushed for even more level than
“bypass” because it is understood that the compressor should be providing some effective headroom
(besides “louder is better” being the oldest trick in the book).
ATTACK
This sets how quickly the compressor reacts and starts attenuating. If set fast (20mS) the compressor
should react to very quick transients like the initial stick hit of a snare drum and can attenuate the “hit”
so the “note” of the drum seems relatively emphasized. If set slower, the compressor will tend to ignore
the fastest transients and react more to the drum resonance and attenuate the “note” of the drum so that
the hit seems more emphasized. Similarly, on a mixed track, if a compressor is set too fast, it will tend to
remove drums, which may help to explain why mastering engineers tend to use medium to slow attack
times and lower ratios.
RELEASE
This sets how fast the compressor returns back to zero after attenuating. Typically engineers have used
quite slow releases when the need is to minimize any obvious compressor action or gains changing. For
modern pop music quite often the goal is to have the compressor change gains approximately in time
with the music and the RELEASE control setting becomes important for this. On the other hand, many
of us were trained to avoid having compressors “pump” and sound like they are breathing. Another
(maybe too) common use of compressors is to maximize the apparent volume and for this one generally
wants very fast release settings so that after reducing peaks the compressor returns to maximum levels
as quickly as possible. And by “as possible” there is a practical matter regarding the tendency of