Quest Engineering | QTA 1480P | User manual | Quest Engineering QTA 1480P User manual

Quest Engineering QTA 1480P User manual
Q-Tech
Q-Tech Commercial Series
QTA 1360P/1480P
Power Amplifiers
User Manual
WARNING
THIS APPLIANCE MUST BE EARTHED
General Installation
DO NOT run unbalanced high impedance
microphone cables near mains, data,
telephone or 70/100V line cables.
DO NOT run 70/100V line cable near data,
telephone or other low voltage cables.
DO NOT exceed 90% of the amplifiers output
power when using 70/100V line (speech only).
DO NOT exceed 70% of the amplifiers output
power when using 70/100V line (high level
background music).
IMPORTANT
The wires in the mains lead are coloured In
accordance with the following code:
Green and Yellow: Earth (E)
Blue:
Neutral (N)
Brown:
Live (L)
As the colours of the wires in the mains lead
of this apparatus may not correspond with the
coloured markings identifying the terminals in
your plug proceed as follows:
The wire which is coloured green and yellow
must be connected to the terminal which is
marked with the letter N or coloured black.
The wire which is marked with the letter L or
coloured red.
If a 13 Amp (B.S.1363) plug or any other type
of plug is used, a 5 Amp fuse must be fitted
either in the plug or at the distribution board.
DO NOT use voice paging horn loudspeakers
for background music unless the loudspeaker
has been specifically designed for this
purpose.
AVOID jointing the microphone cable,
when this is unavoidable make sure a good
screened connector is used.
ALWAYS use balanced low impedance
microphone cable terminating to balanced
inputs on long cable runs.
ALWAYS use a mains grade double insulated
cable for the loudspeaker cable runs when
run in conduit together with power cables.
ENSURE that all loudspeakers are in-phase.
ENSURE that there are no short circuits on
the loudspeaker line before connecting to the
amplifier. It is also advisable to check the final
impedance to the amplifier with a dedicated
impedance meter to determine power draw is
within the amplifiers limits.
QTA 1360P/1480P
User Manual
Contents
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Front Panel Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Rear Panel Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Power Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Main Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Installation Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1
Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Trouble Shooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Technical Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Q-Tech Commercial Series
QTA 1360P/1480P
User Manual
QTA 1360P/1480P
User Manual
Introduction
Description
Congratulations on your purchase of a new
Q-Tech Commercial series amplifier. Quest
Engineering Q-Tech Series amplifiers are
engineered and built to a standard that will
satisfy the most demanding environments of
commercial installation audio.
QTA series power amplifiers cover models
from 120W RMS to 480W RMS. This manual
is for 360W QTA 1360P and 480W QTA 1480P.
For your safety and continuing reliability of
your Quest amplifier, please read all the safety
instructions and familiarize yourself with the
amplifiers functions and installation procedure
section before installing and operating the
amplifier. Quest has paid great attention
to detail in order to maintain strict quality
assurance standards of all Q-Tech Series
amplifiers.
2
It follows that if your audio installation is
completed with the same attention to detail,
your amplifier will deliver its best results.
Please read the section: Constant Voltage
Distributed Speaker Systems Demystified.
Unpacking: Please inspect the amplifier
carefully immediately after unpacking. If
you find any damage, notify your supplier/
dealer immediately. Only the shipper may file
a damage claim with the carrier for damage
incurred during shipping.
User Manual
Q-Tech Commercial Series
QTA 1360P/1480P
•  Easy to use booster Amplifier
• Indicators for signal, clip and protection
• XLR and phone jack input
• Front mounted screw driver gain control
• 8 ohm, 70V and 100V speaker output
• XLR output
• Overload, over temperature, and
speaker short protection.
• 115v-240v AC and 24v DC power in
• 3U height
• 19” rack or table mounted
Rack ears supplied.
• 3 year replacement warranty.
QTA 1360P/1480P
User Manual
Front Panel Layout
1
5 6
4
2
3
1
Power Switch
4
Protection indicator LED - lit when overheating,
short circuiting and overloading
2
Channel volume control
5
Peak indicator LED - lit when max wattage output
and output signal distortion
3
Power indicator LED
6
Signal indicator LED - lit when input signal is
detected
3
Rear Panel Layout
1
2
3
4
5
6
1
Speaker Output Terminal
4
DC Power Supply Terminal
2
2/XLR Input
6
AC Power Input Socket
3
Phone Jack Input
7
Ground Lift
4
XLR Link Output
7
Q-Tech Commercial Series
QTA 1360P/1480P
User Manual
QTA 1360P/1480P
User Manual
Power Source
AC Power Source
The supply transformer has been designed for
AC 240V /115V (±10%) 50 /60 Hz.
DC Power Source
Battery Connection (24Vdc)
When using external batteries, please ensure
the amplifier is grounded via the screw
terminal. (Electrical stability of the system
will be improved by providing a good earth
ground.) When connecting batteries, please
ensure correct polarity.
Speaker Output Connection
The speaker output screw terminal is on the
rear panel. It can connect low impedance 8
ohm, or high-level 70V or 100V speaker. Use
only one of these output connections for
corresponding speaker.
As a guide for the correct gauge of wire, we
recommend the following:
100V
70V
Main Connections
Each input has XLR and Phone jack input.
Use the one you want
4
Pin Assignments:
2
1
AWG25-26 (0.15mm2)
AWG20 (0.5mm2)
Over 200m
AWG18 (0.75mm2)
Up to 50m
AWG24 (0.20mm2)
50m - 200m
AWG17 (1.0mm2)
Over 200m
AWG16 (1.5mm2)
Up to 10m
AWG18 (0.75mm2)
10m - 30m
AWG13 (2.50mm2)
Link Output Connection
2
1
3
3
Plug
Socket
Viewed from Solder
Side of Plug/Soceket
Balanced Audio (3 pole XLR):
Pin 1:
Ground / Screen
Pin 2:
In phase / +ve / Hot
Pin 3:
Out of phase / -ve / Cold
Unbalanced Audio (3 pole XLR):
Pin 1:
Ground / Screen
Pin 2:
Signal
Pin 3:
Ground / Screen (connect to pin 1)
For best performance when using long lines
between microphones/mixer and or amplifier
use balanced lines. These have the effect of
canceling out any noise or hum that may be
induced into the cables.
User Manual
Low
Impedance
(4Ω)
Up to 50m
50m - 200m
Q-Tech Commercial Series
QTA 1360P/1480P
Use XRL (female) to connect booster output
to another amplifier.
A distribution amplifier should be used when
more than 6 amplifiers need to be looped.
QTA 1360P/1480P
User Manual
Installation Practice
Step 1. Take a piece of figure-8 cable,
connect the stripe/coloured wire to the 100V
terminal and the uncoloured wire to the COM
on the amplifier terminal strip.
Step 2. Connect the other end of the wire
(uncoloured) to the Com/EARTH connection
on the ceiling speaker transformer and the
other + (strip) wire to the required voltage
taping.
Step 3. Take a second piece of figure-8 cable
and connect the plain wire to the parallel
COM connection and the other + (stripe) wire
to the parallel output from the transformer
terminal block and connect it in the same way
to the next ceiling speaker.
Step 4. Continue this process until all the
ceiling speakers are connected in a parallel
connection with all the COM connections
and all the wattage connections following a
parallel connection.
2. Incorrect output connection: If you accidentally connect your terminal strip
on the amplifier to the 8 ohm output
instead of the 100/70V line, you will have
distortion and risk damaging the amplifier..
3. Short circuits and no circuits: Check that
your wiring has not been accidentally cut,
miss-connected or generally damaged
in the course of installation. This can be
common with building sites with multiple
trades people installing equipment into the
same ceiling cavities as the audio system.
Operation
After all connections are completed, turn on
the power. If necessary, turn the gain control
on the rear panel to what you desire. We
suggest turning the gain level to maximum
always.
5
Common problems with ceiling
speaker installations
System is distorting. Check for the following
causes:
1. Too many speakers set to too high
a power tapping for the power of
the amplifier Solution: Calculate
the total power draw and re
connect the speakers to a lower the
wattage tapping. (See below)
Some cheap ceiling speakers have
incorrect taping labels. A 10 watt speaker
may really be drawing 15 or 20 watts.
The only way to test this is with an
impedance meter on a single speaker. A
15% discrepancy can mean that a 100
watt system will only be able to power 7
or 8 x10 watt speakers safely. Be aware of
this booby trap. Always plan to have 20%
more power than you think you will need.
Q-Tech Commercial Series
QTA 1360P/1480P
User Manual
QTA 1360P/1480P
User Manual
Trouble Shooting
If the amplifier fails to work as required,
please check the following:
No Power, No Lights
• Make sure amplifier power switch is on.
• Make sure mains power switch is on at
the wall.
• Check the mains and DC fuse.
• Replace with only the correct type and
rating.
Distorted Output
• Check that the speaker type is correct for
the output that you are using (ie. 4-16Ω, or
100V line).
• Check for any short circuits on the
speaker line.
Very Low Output Volume
6
• Make sure that the speaker line is not
shorted.
• Check speaker types and ratings.
• Check that the parallel/mono switch is
correctly set.
Continually Blows Fuses
• Make sure that the speaker line is not
shorted.
• Check speaker types, ratings and if on
correct output.
Amplifier Keeps on Cutting In & Out
• Make sure that there is adequate
ventilation around the amplifier.
• Check the vent slots on the front are not
covered or blocked and the fan on the rear
is functioning correctly.
• Check also speaker types, ratings and for
any short circuits on the speaker line.
User Manual
Q-Tech Commercial Series
QTA 1360P/1480P
Specifications
Type
Booster Amplifier
Model
QTA 1360P QTA 1480P
Output Power (RMS):
Power
Supply
360W
480W
Mains
Voltage
AC 115V or 240V 50/60Hz
Battery
Voltage
DC 24V
Total Harmonic
Distortion
<= 1% @ 1KHz,
rated power
Sensitivity
1V, 100mV @ 10K ohm
Outputs
8Ω, 70V, 100V
Signal to Noise Ratio4 105 dB
Indicator
Power On, Level
AC Power
Consumption
500W
720W
DC Power
Consumption
24A
30A
Dimensions (mm)
450 (W) x 285 (D) x 132 (H)
Weight
15 Kgs
Mounting options
Desktop or 19” rack
17 Kgs
QTA 1360P/1480P
User Manual
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)
100V Line Public Address System
Fig. 1
Remote Speaker
with 100V Line
Transformers
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).
A low impedance terminal will be for
8-ohm speaker installations and is under
no circumstances to be connected to a
transformer type speaker system.
How to calculate the correct
number of speakers and what
wattage connection for a given
amplifier power.
If you connect too many speakers to an
amplifier you will have distortion, overheating
of the amplifier and generally poor
performance. The problem is not really “too
many speakers”, it is more a problem of “too
much wattage draw exceeding the output
capability of an amplifier. A similar problem
would be trying to draw 2,000 watts from
a 1,000 watt generator. Sooner or later….
Expect a system failure.
Let us take a 100 watt amplifier. If you have
20 speakers and you set them at the 5 watt
taping, you will have a total 100 watt draw
which is the maximum output of the amplifier.
This is correct in theory but in practice you
will be safer connecting 18 speakers, not 20.
The reason is that most ceiling speakers draw
more than their claimed wattage.
7
The alternative would be to connect the
speakers to the 4 watt transformer terminal
giving you a theoretical total draw of 80 watts
and thus, plenty of “headroom”. One watt
difference is not very noticeable as far as
output sound pressure level in concerned.
A system that does not distort will give
much clearer voice reproduction than a
louder system that is distorting or loosing
the sibilant frequencies.
There is a formula for testing the potential
power of the system by measuring the
impedance of each speaker and then adding
all the figures to a total impedance, which is
then compared to the amplifier’s expected
impedance/power figures. The quick way is
to just add up all the wattages and then give
yourself 10-20% headroom by reducing the
number of speakers per amplifier or lowering
the wattages slightly.
Q-Tech Commercial Series
QTA 1360P/1480P
User Manual
QTA 1360P/1480P
User Manual
For the benefit of those who want to calculate
the power of the system with a formula. See
below:
Determining power by calculating
total impedance
The alternative to counting the speaker taping
watts is to calculate the total impedance of
the line, which will also indicate the wattage
necessary to drive the system correctly.
The computational formula is voltage squared
divided by impedance:
Power = Voltage2 / Impedance
8
When the speaker line reaches its top voltage
of 70 Volts, the formula is:
Power = 5000 / Impedance (because 70
squared equals 5000).
To measure impedance a dedicated meter is
required. These use a 1k frequency to send an
alternating current through the transformer(s).
The resulting figure indicated by the meter’s
dial can be cross referenced with the meter’s
impedance chart to see what value should be
expected and the power that will be required.
High impedance of speakers and output calculation table for 100Volt systems
Output
Impedance
Output
Impedance
Output
0.1W
100KΩ
10W
1KΩ
40W
Impedance
250Ω
0.5W
20KΩ
15W
667Ω
50W
200Ω
1W
10KΩ
20W
500Ω
75W
133Ω
2W
5KΩ
25W
400Ω
100W
100Ω
3W
3.33KΩ
30W
333Ω
150W
66.7Ω
5W
2KΩ
35W
286Ω
200W
50Ω
(100V plan) P = E x E / Z = 100x100 / Z = 10,000 / Z
P: Power(W), Z : Impedance (Ω), E : 100V(Designed voltage of a general-use amplifier)
User Manual
Q-Tech Commercial Series
QTA 1360P/1480P
www.questaudio.net
Quest Engineering Pty Ltd
86 Derby St. Pascoe Vale VIC 3055
Ph 613 9354 9133 | Fax 613 9354 9233
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