Quest Engineering QX-4750 Manuel utilisateur
QX-4750 USER MANUAL | 01QUESTAUDIO.NET QUESTAUDIO.NET
QX-4750
USER MANUAL
QX-4750 USER MANUAL | 02QUESTAUDIO.NET
PRODUCT OVERVIEW
The Quest Engineering QX-4750 is a 4 channel 2RU power amplier suited for any application requiring
superior performance and reliability. Ideal for multiple zone applications providing commercial sound
installations with clean and reliable power. The QX-4750 provides 750 watts per channel of operation
into 4 ohm loads and can bridge channel outputs that can be congured to deliver 1500 watts of power
to either low- or high-impedance loads. High and Low pass lters, limiters and standby are available per
channel with fast 1ms wake up time. For high end commercial, AV or domestic applications, the QX range
of ampliers provide superior class D performance with proven reliability without compromise.
SAFETY PRECAUTIONS
•Please read the instructions in this section carefully before use.
•Ensure all instructions in this manual are observed as all information contained within is very important.
•It is also highly recommended that this manual is retained for future reference.
SAFETY SYMBOL & MESSAGE CONVENTIONS
The safety symbols described are used in this manual to prevent bodily injury and property damage which
could result from mishandling. Before operating this product, please read this manual rst, in full so you
that you are thoroughly aware of any risks.
Indicates a potentially hazardous situation which,
if mishandled, could result in serious personal injury or death.
QX-4750 USER MANUAL | 03QUESTAUDIO.NET
•Do not expose the unit to any moisture
whether rain, water, or other liquids. Exposure
to moisture could result in damage to internal
components or electrocution\circuit failure.
•Do not cut, kink, or otherwise damage or
modify speaker cable. Ensure a speaker cable
with a core diameter of at least 2.5mm2 is used
for specied performance.
•Do not install or place speaker cables or
this device near heaters, high trac areas
or any area where the cables or device can
be damaged.
•Avoid installing or mounting speaker
boxes, ampliers, electronics or cabling
in unstable locations.
•In the event of storms and/or lightning, ensure
all devices are disconnected from mains power
in order to prevent damage to any of the units
in the system.
•When cleaning the unit, ensure it has been
disconnected from any power source and that
only a dry cloth is used. Do not use any aerosol
or liquid-based cleaners.
•Ensure all electronics are electronically
grounded (earthed) to a safety ground
terminal in order to avoid electric shock.
Do not ground any device to a gas pipe as
this may result in re.
•Servicing of all electronics should only be
carried out by a certied Quest technician.
Please consult your original place of purchase
to nd the location of your nearest Quest
service centre.
•When installing ampliers and/or other
electronics only use the hardware specically
designed for this product.
GENERAL CAUTION
QX-4750 USER MANUAL | 04QUESTAUDIO.NET
FRONT PANEL CONTROLS
HPF
O: Amplier passing full range signal
On: 80Hz High Pass Filter Active (24dB/Oct)
LPF
O: Amplier passing full range signal
On: 100Hz Low Pass Filter Active (24dB/Oct)
LIMIT
O - Amplier will not limit
On - Amplier will limit to prevent clipping
A-STBY
O - Amplier will not enter power saving mode
On - Amplier will enter sleep mode after 25 minutes of
no signal
BRIDGED-MONO
O: Amplier operating as 2 individual channels
On: Amplier operating in bridged mono mode
CH1
CH2
CH3
CH4
Rotary gain control
LIMIT/CLIP
Orange: Amplier is limiting signal or muted if in
standby mode
Red: Amplier is clipping
SIGNAL Green: Signal is detected
PROTECTION Orange: Amplier is in protect mode
QX-4750 USER MANUAL | 05QUESTAUDIO.NET
REAR PANEL CONNECTIONS
CH1 Input/Link
CH2 Input/Link
CH3 Input/Link
CH4 Input/Link
XLR/Phoenix/Euroblock
CH1 Output
CH2 Output
CH3 Output
CH4 Output
SpeakON
Mains Connection PowerCON
Blank Plate for Expansion Module (optional)
QX-4750 USER MANUAL | 06QUESTAUDIO.NET
BASIC OPERATION GUIDELINES
Due to the advanced power saving feature of the QX-4750, the amplier has been designed to power
from the mains with no additional switch. The amplier has a removable grille on the front panel. The
grille is held in place magnetically and can easily be removed without tools to access controls to engage
a number of modes which are described in the next section. High Pass and Low Pass lters can also be
activated to provide basic frequency dividing functions, these are most commonly used in a system with
sub-woofers.
To avoid harm to connected speakers it is important to not clip the amplier for extended period of times.
Clipping occurs when the input signal is excessive and overloads the input or output of the amplier.
To avoid clipping reduce the level of the input. The amplier has a selectable limit option which can be
engaged to help avoid clipping and it is recommended that this mode is used if the potential exists for
extended periods of clipping.
The amplier has a protection circuit which activates when a fault condition exists. The LED will stay
illuminated until the fault is resolved. The protection circuit activates to help prevent damage to the
amplier and connected speakers. Common causes can be shorted wiring or faulty speakers. If the
Protect light illuminates disconnect the amp from power and then disconnect the speakers. Reconnect
the amp to mains and check the status of the protect LED, if the LED has not turned back on then check
the speakers and cabling for faults.
If the amplier is to drive high impedance speaker loads (70 or 100v) then Bridge mode must be enabled,
it is possible to have half the QX-4750 running high impedance loads and the other half running low
impedance loads, e.g., Ch 1&2 Bridged 70/100v and Ch 3&4 connected to separate 4/8 ohm loads or
bridged to 4/8 ohm or 70/100v.
QX-4750 USER MANUAL | 07QUESTAUDIO.NET
OPERATION MODES
Active Mode is indicated by a Blue LED, the amplier is connected to power and ready to pass signal.
Mute mode puts the amp into a “light sleep” and occurs when the Standby option has been selected and no signal has been
detected for 10mins, if the amplier detects signal it will wake within 1ms. When no signal has been detected for 25 mins full sleep
mode will activate.
The Orange LED’s indicates the amplier is in Standby, a power saving mode. This mode can be enabled by toggling the under
panel A-STBY switch from O to On. In this mode if no signal is detected for 25 mins the amplier will “sleep” and wake within
660ms of detection of signal.
QX-4750 USER MANUAL | 08QUESTAUDIO.NET
INPUT WIRING
Balanced Input Wiring Unbalanced Input Wiring
Balanced Link Wiring Unbalanced Link Wiring
Bridged-Mono Balanced Input Wiring
If the amplier is to be used in Bridged Mono
mode for low impedance speakers or to drive
high impedance loads (70-100v), the under panel
Bridged Mono control switch should be in the On
position and input connection wired to input 1 for
channels 1&2 and channel 3 for channels 3&4.
This can easily be noted by observing the marking
(BM) on input connectors 1&3.
QX-4750 USER MANUAL | 09QUESTAUDIO.NET
CH2: 1+1-
CH4: 1+1-
CH1: 1+1-
CH2: 2+2-
CH1/CH2: 1+2-
CH3: 1+1-
CH4: 2+2-
CH3/CH4: 1+2-
Stereo Bridged-Mono Mode
OUTPUT WIRING
QX-4750 USER MANUAL | 10QUESTAUDIO.NET
SPECIFICATIONS
MODEL PER CHANNEL BRIDGED-MONO MODE
LOAD 8Ohm 4Ohm 70V
(22Ohm)
100V
(33Ohm) 8Ohm 4Ohm 70V 100V
Maximum Dynamic Power
(@1KHz, 1% THD) 4x 400W 4x 750W NA NA 2x 1500W 2x 1400W 2x 1500W 2x 1500W
Maximum Continuous Power
(@1kHz, 1% THD) 4x 400W 4x 750W NA NA 2x 1500W 2x 1400W 2x 1500W 2x 1500W
Features
Wake On Music, Auto-Mute
(1ms wake-up), Limiting on
High Temperature
Amplier Protection Systems
Thermal protection,
Over-Current Protection,
DC Protection, HF Protection
Mains Input Voltage Range 85VAC - 265VAC
Standby Power Consumption 4.8W
Muted Power Consumption 16W
Idle Power Consumption 28W
Standard Power Consumption
(Pink Noise@ 1/8th Rated
Power, 8Ohm)
160W
Output Connector SpeakON
Mains Connector powerCON
Dimensions (H x W x D) 88 x 482 x 416 mm
(3.5 x 19 x 16.4")
Weight 10.2kg (22.5 lbs)
Accessories Mains Cable, Feet, User Manual,
Phoenix Plugs
Frequency Response 20-20kHz (+/-0.3dB)
Peak Output Current 40A
Dynamic Range 111dB (A-weighted)
Noise Level -72dBu (A-weighted)
Distortion (1kHz@1W/8Ohm) 0.004%
Distortion (1kHz@50W/8Ohm) 0.003%
Crosstalk (1kHz@1W/8Ohm) -90dB
Gain 26dB/32dB
Maximum Input Level +24dBu
Input Type Analogue Balanced XLR +
Optional Expansion Module
Link 6-pin Phoenix (3.81mm pitch)
Input Sensitivity +7dBu/+4dBu
Input Impedance 10kOhm
Output Resistance 6.5mOhm/13mOhm
Front Controls
Volume Adjust, 80Hz HPF
Enable, 100Hz LPF Enable,
Bridged-Mono Enable, Limiter
Enable, Auto-Standby Enable
Indicators (LEDs)
Blue/Orange Active/
Standby
Orange Protection
Green Signal
Detection
Orange/Red Limiter/Clip
Cooling Fan cooled, temperature
dependent
* All specications were measured at 240VAC
** Quest Engineering reserves the right to make changes in
specications, or products without prior notice.
*** The gures shown above are ‘real world’, usable specications and
are conservative as a result. Quest Engineering does not believe in
portraying misleading or exaggerated specications.
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