4.2 The Peak Limiter Section
How fast is the compressor to react to a signal which is above the threshold point? This is determined by the attack
time. A longer attack time is advisable to process low frequencies while shorter attack time is preferable for high
frequencies. IN this way you will avoid undesired dynamic distortion. But what about if you are mixing a program
with a wide range of frequencies? IN this case you should choose a setting that would benefit the low frequency
better. Well, life is not that easy for conventional compressor/limiters. Ok you handle an audio signal made by a
wide range of frequencies and you have chosen a longer attack time. But, if using your ACL4 as a limiter the
fast high frequencies will pass through untouched because the attack time is too slow and such transients could
cause distortion when the unit is connected to broadcast devices or taper recorders. The solution in ACL4 is
represented by our Smart Gain Control (SGC) limiter circuit. The curve in bold is the output signal and the dashed
curve above it is the input signal. The area in between the two is the amount of gain reduction.
The unit will activate the limiter when the signal exceeds the threshold for more than 20 microseconds. Then 1
second after that the signal is below threshold again, reduction goes back to 0dB and in this case input and output
signals are again identical.
Chart. 5 SGC characteristic of the limiter section
5. INSTALLATION AND CONNECTION
5.1 Mains Connection
ACL4 is provided with dual voltage plug. You must check the power supply Voltage available in your Country
before connecting the power cord in the wall outlet. Please see Page 7, paragraph 12 for further info.
5.2 Audio
onnection
C
The ACL4 Compressor/Limiter is equipped with balanced XLR connectors as well as 1/4" phone jack and can be
connected with other units in different ways to support a vast range of applications without experiencing a signal loss.
a. Wiring Configuration
Both types of connectors available on ACL4 can be wired in balanced and unbalanced modes. Please see following
drawing for details:
For 1/4" Phone jack
9
Peak Limiting
6ms
15ms
Level
Program Limiting
Input
Release
Output
approx. 1 s
Threshold
t/ms
30
20
10
Pic. 3
TS Type Unbalanced
Sleeve
Tip
+
TRS Type Balanced
Tip
Ring
Sleeve
+
-
TRS Type Unbalanced
Tip
Ring
Sleeve
+
