5 Notes on Operation
5.1 General Notes
Provide for sufficient space behind and in front of the amplifier, so that air can circulate through the
device unobstructed. Cool air is sucked through the slots at the left and right side of the front
panel. First connect the amplifier with the mains power connection after input/output are wired.
Allow the amplifier a warm-up phase of 15 minutes after switching on, for the stabilization of its
operating points.
5.2 Operating Voltages
Before the "amplification" begins, some considerations relating to the selection of the operating
voltage are recommended for an effective and safe operation of the A1230-01 (see also White
Paper No.1: Hubert Power Amplifier).
The amplifiers have two operating voltages:
•
High operating voltage (±90 V) for high output voltages and low load currents
•
Low operating voltage (±45 V) for low output voltages and high load currents
In order to keep the power loss of the amplifier low, the operating voltage should always be
selected according to the load.
Example:
The load current IL should be 2 ADC.
Load 1: RL = 25
For IL = 2 ADC an output voltage UA = 50 VDC is required (UA = IL * RL). The power loss PV at
the power amplifier results from the voltage drop at the power stage multiplied by the current
through it.
PV = (UB - UA) * IL = ( 90 V - 50 VDC) * 2 ADC = 100 W
Load 2: RL = 5
For the same load current IL = 2 ADC an output voltage UA = 10 VDC is required. The power loss
at high operating voltage is thus:
PV = (UB - UA) * IL = ( 90 V - 10 VDC) * 2 ADC = 160 W
If a change is now made to the operating voltage Ulow, the following display results:
PV = (UB - UA) * IL = ( 45 V - 10 VDC) * 2 ADC = 70 W
As you can see from this simple example for DC, it makes more sense to use the amplifier at low-
impedance loads with low operating voltage. For AC signals, the calculations would be much more
complicated, but the ratios remain basically the same. Particularly with complex loads, a phase
shift between output voltage and current is an aggravating factor, which leads to additional losses
A1230-01
Notes on Operation
Page 16
