dbx 160SWP - Manual (Page 2)

Many audio compressors employ an “Auto” mode to set the attack and release
of the VCA so that the compressor will be well behaved when used in a variety
of situations such as compressing vocals, piano, or program material. “Well
behaved” means that pumping and breathing are minimized and that dynamic
distortion, caused by low frequencies modulating the control line feeding the
VCA, is not audible. The “Auto” mode works beautifully for most compression
needs, however, we often need to compress signals that require a quicker
attack time to catch leading edge transients such as a snare drum hit.
Many compressors on the market have manually adjustable attack and release
controls to give the engineer greater creative control over how the
compressor reacts to a signal. dbx compressors having manual controls
include the 266/266XL, 1066, 165/165A, the MC6, and new dbx 160S/160SL. If
we look at the markings around the dbx 1066 attack and release controls, we
find the attack range is 3 to .04 dB/msec and the release range is 250 to 5
dB/sec. These markings may seem cryptic at first but, upon further investi-
gation, we find that an attack setting of 3 dB/msec means that the VCA will
reduce its gain at a rate of 3 dB for every millisecond (0.001 second) of time,
or 3000 dB for every second of time. Whereas a release rate of 250 dB/sec
means that the VCA will release its gain reduction at a rate of 250 dB for every
second of time. These attack and release times may seem incredibly fast, but
believe it or not, they are not fast enough for all compression needs. So, why
not just speed up the range of the attack and release controls?
Well, let’s examine the dbx 165/165A. Her attack and release times ranges are
400 to 1 dB/msec and 4000 to 10 dB/sec respectively. Anyone who has used
the 165/165A in the manual attack/release mode knows that it has an
extremely wide range of control and how effective it is for compressing fast
transients by dialing in a fast attack time. However, they also know how easy
it is to get a “bad” sound out of the 165A if the attack and release controls are
AutoVelocityª Dynamics and the dbx 160SL White Paper - November 1998 Page 1
AutoVelocity™ Dynamics and the dbx 160SL
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