Technical data

28
REFERENCE - Threshold Oset
The analog audio level of the alpha compressor depends on the studio environment it is used in. In the ma-
jority of cases it depends on the DA converter used, because the output stages of the converter determine
the analog level. As there is no binding norm for it, this level can be at +4dB, +6dB, +10dBu, +12dBu or even
+15dBu. To make sure that the Threshold controller actually covers its complete adjustment range it can be
adjusted to those dierent levels.
When is an adjustment necessary?
1. At low Ratio values (1:1,3), the Threshold controller is al-
most completely turned clockwise and the Gain reduction is
still too low
2. At higher Ratio values (1:2,5), the Threshold controller is
turned completely counter-clockwise, but nevertheless Gain
reduction already sets in
In order to adjust the internal Threshold Oset, the rst thing
to do is to open the top cover with the adequate Torx screw-
driver. Before the adjustment can be done the unit has to be
powered up for at least 15 minutes to reach a stable work-
ing temperature. Please make sure to disable the MS and Link
functions. Now send an audio signal into the compressor and
set the Attack to approx. 24ms and the Release to 300ms.
On the upper circuit board there is a blue trimmer labeled THRESHOLD OFFSET situated directly behind
the Threshold potentiometer (the yellow arrow in the gure). In the rst case (too little Gain reduction) the
trimmer has to be turned clockwise to raise the amount of Gain reduction. In the second case (too much
Gain reduction) the trimmer has to be turned counter-clockwise. In order to reassure that the adjustment
range now really ts, it is recommended to repeat the above-mentioned test with the Threshold controller
in extreme left/right position. The same procedure should also be applied to the right channel, of course.
REFERENCE - Threshold Offset & Threshold
Threshold
The diagram shows dierent Threshold settings in Feedback mode. The Threshold and the Ratio
are always interdependent: On high Ratios the Threshold will usually be set to lower values in or-
der not to produce too much Gain reduction, and on lower Ratio settings the Threshold controller
will be turned more to the right. The complete Threshold range covers 33dB which enables the
user to make very sensitive settings in reasonable steps at any time.
-20 +20-17.5 -15 -12.5 -10 -7.5 -5 -2.5 +0 +2.5 +5 +7.5 +10 +12.5 +15 +17.5
-20
+20
-18
-16
-14
-12
-10
-8
-6
-4
-2
-0
+2
+4
+6
+8
+10
+12
+14
+16
+18
dBu
dBu