Quest Engineering QTA 2120P, User Manual

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QTA 2120P/2240P
User Manual
User Manual Q-Tech Commercial Series
QTA 2120P/2240P
6
Technical Notes
Constant Voltage Distributed
Speaker Systems Demystified
In a typical paging and background music
speaker installation, quantity loudspeakers
are placed across a single amplifier in a
parallel wiring configuration (see Fig 1.).
Each ceiling speaker will contain a small
transformer and you will notice that the
connection block near the transformer will
have a common terminal (C or earth), and a
number of wattage terminals.
Connect the wattage setting terminal for the
desired acoustic output (volume) level you
need from each individual speaker.
This will be a 100V setting in Europe and
most of Asia and 70V in the USA. (See the
explanation below)
Often some speakers need to be set at
different volume output levels, and the
calculations involved in determining the actual
load impedance at the amplifier’s output
can be quite involved but there is a simple
technique for not overloading the amplifier
As for the amplifiers, there are two common
standards, 100 Volt line in Europe and Asia
and 70 Volt line on the American continent.
For the purpose of simple calculations, we will
use the European standard for this exercise.
On the rear of a 70/100V amplifier you will find
an output terminal strip. This terminal strip
will contain a number of + voltage outputs
(70V 100V) and a terminal at one end for the
negative return wire (COM).
Specifications
Type Booster Amplifier
Model QTA 2120P QTA 2240P
Output Power
(RMS):
120W x 2 240W x 2
Power
Supply
Mains
Voltage
AC 115V or 230V 50/60Hz
Battery
Voltage
DC 24V
Total Harmonic
Distortion
<= 1% @ 1KHz, rated power
Sensitivity
XLR, Phone Jack (balanced) 1v
@ 10K ohm
Outputs
8
Ω
, 70V, 100V
Signal to Noise
Ratio4
86 dB
Indicator Power On, Level
AC Power
Consumption
440W 880W
DC Power
Consumption
8A 15A
Dimensions (mm) 450 (W) x 184 (D) x 132 (H)
Weight 14.3 Kgs 18.8Kgs
Mounting
options
Table top or 19” rack mountable
100V Line Public Address System
Remote Speaker
with 100V Line
Transformers
Fig. 1