Apex N.V. GX 230 User manual

APEX GX Series
Graphic Equalisers
GX 230
USER MANUAL
APEX nv

3
Section 1 : Contents 3
Section 2 : Introduction 5
2.1 The GX 230 5
Section 3 : Performance Highlights 7
Section 4 : Installation 9
4.1 Unpakking the unit 9
4.2 Checking the mains voltage 10
4.3 Setting the mains voltage 10
4.4 Replacing the mains fuse 10
5.5 The rear pannel 11
5.6 Rack mounting 13
Section 5 : Signal connections 15
5.1 Input 15
5.2 Output 16
5.3 Grounding 17
Section 6 : The Equaliser 19
Section 7 : General operating instructions 21
7.1 Introduction 21
7.2 Level control, O/load and power 21
7.3 HP filter 22
7.4 Graphic equaliser 22
Section 8 : Specifications 23
Section 9 : Maintenance and service information 25
Section 10 : Warranty 27
Contents
1

4

5
Introduction
The GX 230 The APEX GX230 is a dual channel 30 band 1/3 octave graphic
equaliser, incorporating our newly developed DLT hybrid circuits.
A high-pass filter precedes the equaliser in each channel and is
switchable in and out of the signal path. The unit is built to the
highest professional standards both for electronics and
mechanics.
The heart of each graphic equaliser is a bank of 30 bandpass
filters, one filter for each 1/3 octave frequency. Conventional
equaliser designs use discrete components to realise these
bandpass filters. Although it is possible to build good equalisers
with this technology using precision components, far better results
can be achieved with dynamically trimmed hybrid circuits. This is
what DLT stands for: Dynamic Laser Trimming.
At the factory, each filter of the graphic equalisers is laser trimmed
to match “mother nature’s” prescription for ideal response. This
results in perfect combining of the individual filter response curves
and, therefore, a perfectly flat amplitude and phase response.
All the filter components are incorporated on the hybrid circuits. As
a final production step, each bandpass filter is adjusted for the
correct 1/3 octave centre frequency and bandwidth, using a
specially developed trimming algorithm for adjusting the centre
frequency and bandwidth simultaneously. Incorporating all filter
2

6
components on the hybrid circuits yet has another important
advantage : because of the largely reduced number of soldered
connections, reliability is boosted to an extent only exceeded by
integrated circuits (some call it “fit and forget technology”).
The controls of the graphic equalisers provide up to 12 dB of
reciprocal cut and boost at the 30 distinct centre frequencies. The
filters of the GX230 preserve optimal filter bandwidth, whatever the
settings of the controls.
Because of this ‘constant Q’ circuitry, filter response does not
broaden at low cut or boost settings (fig 1.2). In this way filter
interaction is minimised and the ‘graphic’ qualities of the equaliser
preserved.
The graphic equalisers of the GX230 are switchable IN and OUT
of the signal paths. The complete unit can be bypassed by
switching it off. The failsafe relays will react as if there were a
mains failure and will link the input of each channel to its
corresponding output.
The GX230 has electronically balanced inputs and balanced,
floating output stages. Each output circuit actually simulate a
transformer with a 10KOhm impedance to ground for each leg.
Both the input and output circuits are factory adjusted for optimum
balance at low and high frequencies. This results in increased
interference immunity of the unit.
The overall gain of each channel of the GX230 is variable from

7
Performance Highlights
•Two independent channels.
•30 band constant Q precision DLT graphic equalisers
•Switchable 30Hz highpass filters with 18dB/oct slope.
•Graphic equalisers in-out switchable.
•Switchable scale 6/12 dB on graphic equalisers.
•6 dB of gain available.
•Extremely low distortion and noise.
•True differential input circuitry.
•Effective HF interference cancelation on in- and outputs
through perfectly HF balanced stages
•XLR in- and outputs.
•Accurate “peak-stretching” overload indicators.
•Failsafe bypass.
•Earth-lift switch.
•Power transformer with low flux windings and magnetic
screening, reducing magnetic stray field to other units.
•Wide mains-voltage range.
•Professional parts and construction
3

8

9
Installation
Unpacking the unit
In addition to these operating instructions and the GX 230
equaliser, the packaging also contains :
• A power cord (see note for U.K.).
NOTE
This apparatus must be earthed.
The wires of the mains lead are coloured in accordance with the
following code : Green and yellow : Earth
Blue : Neutral
Brown : Live
As the colours of the wires in the mains lead may not
correspond with the coloured marking in your plug proceed as
follows ;
The equaliser comes in a cardboard safety box, specially
designed for protection of the unit against damage during
transport. Save all the packing materials for future use if you
ever need to ship the unit again.
Please inspect the unit carefully for any signs of damage
occurred during transport. Your GX230 has undergone stringent
quality control inspection and tests at the factory. It left in perfect
condition. If damage is found, notify the transport company
immediately.
Only you, the consignee, may institute a claim against the carrier
for damage during shipment. Make sure to retain the damaged
4

10
Checking
the mains voltage
Setting
the mains voltage •Remove the plug from the wall socket and check if the mains
fuse is of the correct rating.
Delivery position is 220 V / T315mA Wickemann 19195 in all
cases
•Withdraw the fuse holder from the equaliser by turning the
locking screw a half revolution counter clockwise and pull out
the fuse holder of the socket
•Remove the old fuse and replace with fuse of the correct rating
• T630 mA (slow blow fuse) Littlefuse 213.630 for 100/120 V
• T315 mA (slow blow fuse) Littlefuse 213.315 for 220/240 V
Replacing
the mains fuse
•Check if the voltage selector on the rear of the equaliser
indicates the correct supply voltage before connecting the
equaliser to the mains.
NOTE