Universal Audio LA-610 Channel Strip - Manual (Page 12)

7
Voltage Select
The LA-610 can operate at 115 V or 230 V. To change the mode, wait 5 minutes after
power down, unplug the AC power cord from the rear chassis. Remove the top cover.
As shown below, the Voltage Select Cable can be plugged into one location for 115V
operation or moved to the 230V Connector for 230V operation. This figure shows the
unit configured for 115V operation. The connector is part of the wiring that comes from
the power transformer located at the rear of the LA-610 next to the main AC power inlet.
When changing operating voltage, the fuse value must be changed as well. Make sure
the LA-610 is properly set for the voltage in your area before applying AC power to unit!
Figure 4: 115V / 230V Voltage Select Jumper
Compressor Theory of Operation
Compressor Basics
Before we dig in to a description of the compressor circuit, it is useful to examine the
general characteristics of compressors and review some terminology. The chart below
(Figure 4) depicts the input/output characteristics of a compressor, an expander and a
perfect amplifier. When operated within its specified range, an amplifier provides a
constant amount of gain regardless of the level of the input signal. In figure 4 below, the
middle line depicts a perfect amplifier with a gain of 10 dB. To see this, notice that a
signal with an input level of –30 dB will result in an output level of –20 dB, which is an
increase of 10 dB. Similarly, an input level of 0 dB will result in an output level of 10
dB, hence the gain stays fixed at 10 dB regardless of the input level.