BSS Audio OPAL Series DPR-522 Owner's Manual - Manual (Page 22)

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7.0 Beginners guide
Beginners guide
7.1 What are gates
for?
Put simply, a noise gate is a device that blocks or switches off a signal if that
signal falls below a certain preset level. Originally noise gates were used for
just that, gating or removing noise from recordings. For example traffic rumble
in studios, or electronic noise from old tape loop echo chambers.
Noise gates or gates function by taking the main input signal and splitting it
into two paths. One path passes through an electronic switch to the output and
is not modified in any other way. The other, called the KEY SIGNAL is
processed to provide a ‘trigger’ for the switch. Once the main signal has
exceeded the user selected THRESHOLD and provided the trigger, the gate
will open. In modern gates the switch is replaced by a fader circuit, thereby
allowing the gated signal to be faded up and down, often quite slowly. The
fade up rate is defined by an ATTACK control, the fade down by a RELEASE
control. This fading action can be important, as the ear is much more sensitive
to abrupt changes in level than gradual ones.
One major application for modern advanced gates is the separation of sounds
so that they may be processed separately, for example in a multi-miked drum
kit. In this case each drum would have a separate microphone, the intention
being to have independent control of the level and tonal balance of each
drum. Unfortunately, due to the close proximity of the microphones, there will
be significant bleed of sound from one drum to another. Gates are used to
prevent this. They are set up to only open when their particular drum is hit.
Unfortunate it is sometimes not easy to set a gate up to only trigger on the
desired signal, quite often the wanted and unwanted signals are close to each
other in level. This is where key filters are useful. Key filters are setup to
condition the key signal by filtering out signals that don't originate from the
drum in question, thereby increasing the difference between adjacent drums
and making the job of ensuring that only the correct drum triggers the gate
easier.
Another use for gates is in the reshaping of existing sounds. Quite often
sampled sounds will be used in recording. Sometimes these sounds may have
an inappropriate attack or release sound for their intended purpose. By
triggering a gate on the sample, and with careful setting of the attack and
release controls, a new envelope, that produced by the gate, will be imparted
to the sampled sound.
Additional features are often added to contemporary gates, for example, the
ability to trigger the gate with a signal that is not the same as the one being
gated, or using external switches or logic signals to open or inhibit the gate.
By introducing the possibility of control via a computer or sequencer, these
facilities add enormously to the versatility of the unit and take its application
into areas far removed from the original intention of the designers of the first
‘noise gates’.
7.2 Basic operation These instructions are primarily designed to help you get started using the
DPR-522.
The front panel is split down the middle into two identical sections or
channels. The left hand section will be referred to as channel 1, and the right
hand section as channel 2. There is no difference in operation between these
two channels, and so all the discussions will equally apply to both. The
exception to this is STEREO LINK mode (described in section 6.15).