Drawmer DF330 Universal Noise Filter - Manual (Page 9)

DF330 OPERATOR’S MANUAL 7
OPERATION
The unit should be connected in line with the signal to be processed, preferably via the
console's insert points. See the section 'INSTALLATION' for details.
Setting up is identical for mono or stereo operation, the only proviso being that for stereo
use, the Stereo Link switch must be on and both sets of controls should be set similarly.
The expander is best set up independently of the filter, so at this point, the filter should
be switched out. Now the user must decide whether a sharp or progressive action is
required. For a sharp gate-like action, a high ratio and high degree of attenuation should
be chosen, together with a fast release time. If, on the other hand, a less obtrusive
action is called for, a lower ratio combined with the minimum attenuation setting and a
slower release time will allow the threshold level to be increased slightly so that dynamic
range expansion can be implemented on low level signals. This choice depends entirely
on the nature of the material being processed, so a period of experimentation is
recommended which will enable the user to become familiar with the operation of the
DF330 and obtain the best possible results from it.
It is essential that the expander should only affect low level signals close to the noise
floor and so careful setting of the threshold is essential.
The attack time of the expander is completely automatic, adjusting itself to suit the
attack characteristic of the signal being processed, regardless of frequency. This will be
of particular value when cleaning up a vocal track. Once the expander is set for optimum
performance, it should be switched out and the filter switched in. The filter can be used
in either Manual or Auto mode, depending on the type of material being processed.
In the Manual mode, the threshold should be set so that moderate to loud sounds cause
the filter display to show the full 20kHz and this will probably fall to 10 or 12kHz between
beats in the case of pop music. The next step is to play a quieter part of the programme
and check that the filter action is having a beneficial effect on the noise content. This
may be checked by switching the bypass switch and comparing the treated and
untreated signals.
If the noise is still too obtrusive, a higher threshold level may be set, but if on the other
hand there is a noticeable lack of high frequencies and noise is not a problem, then the
threshold level may be reduced. On very noisy programme material, the setting up
procedure is a matter of choosing an acceptable compromise between background noise
and some loss of high frequency definition.
In Auto mode, the Threshold control should be set up with only background noise being
fed into the unit; in the case of a recording, this might be a section of blank tape before
the programme starts. The filter Threshold should be turned clockwise until the filter just
starts to open in response to the noise and then it should be backed off slightly so that
it is once again closed. This will be evident by watching the filter frequency display. At
this stage, the programme material may be introduced and operation should be
completely automatic.
Signal above the threshold is analyzed for frequency content and the filter is in turn
controlled so that it tracks the upper frequency limit of the programme. Because the filter
response is extremely fast, sudden changes in the spectral content can be
accommodated, and, because the signal level has little effect on the filter action, the
filter will track the frequency of the input even through fades. When the signal level