Apex Digital PE 232 MKII User manual
APEX PE Series
Paragraphic Equalisers
PE 232 MKII
USER MANUAL
APEX nv
Schoebroekstraat, 62
3583 Beringen - Belgium
Tel: +32 89 28 61 91
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Section 1 : Contents 3
Section 2 : Introduction 5
2.1 The PE MKII series 5
Section 3 : Performance Highlights 9
Section 4 : Installation 11
4.1 Unpakking the unit 11
4.2 Checking the mains voltage 12
4.3 Setting the mains voltage 12
4.4 Replacing the mains fuse 12
5.5 The rear pannel 13
5.6 Rack mounting 14
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 23
7.1 Introduction 23
7.2 Level control, O/load and power 23
7.3 HP and LP filters 24
7.4 Parametric 24
7.5 Graphic equaliser 26
7.6 Specific applications 27
Section 8 : Specifications 29
Section 9 : Maintenance and service information 31
Contents
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Introduction
The PE MKII serie The APEX PE MKII series combines a graphic equaliser section
with a parametric filter section. Wide-range Butterworth low and/or
high pass filters precede the equalisers for added versatility and
shaping of the response curve near the edges.
The heart of each graphic equaliser section is a bank of 30
bandpass filters at distinct ISO centre frequencies or one filter for
each 1/3 octave frequency.
Perfectly flat amplitude and phase response is obtained by using
our DLT thick film hybrid circuits which surpasses the results and
quality of discrete components.
DLT stands for Dynamic Laser Trimming: at the factory, each filter
of the graphic equaliser is adjusted for optimum 1/3 octave filter
centre frequency and bandwidth by means of a special developed
trimming algorithm. Adjusting the centre frequency and the
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Incorporating all filter components on the hybrid circuits has the
advantage that the number of soldered connections is largely
reduced, boosting the reliability to an extent only exceeded by
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The controls of the graphic equaliser provides up to 12 dB of
reciprocal cut and boost at the distinct ISO centre frequencies. The
filters of the PE series preserve optimal filter bandwidth whatever
the settings of the controls are.
Because of this `constant Q’ circuitry, filter response does not
broaden at low cut or boost settings. In this way filter interaction is
minimized and the `graphic’ qualities of the equaliser preserved.
The individual filters of the graphic equaliser combine smoothly
together and result in a continuous response curve, free from
The strength of the parametric filters is the possibility to control Q,
frequency and bandwidth. A -45 to 15dB of non-reciprocal constant
Q is achieved by adding (boosting) or subtracting (cutting) the
output of a variable-state bandpass filter from the filter’s input. This
technique results in a broader boost than cut curves and makes it
possible to create very narrow notches, almost inaudible and
therefore without the sound-colouration often found with reciprocal
filters. One of the possible applications of those notch filters is
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All filter and equaliser functions of the PE232MKII are switchable
IN and OUT of the signal paths. The complete unit can be
bypassed by switching it off. The fail safe relays will react as if
there were a mains failure and will link the input of each channel to
its corresponding output.
The PE232MKII 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 PE232MKII is variable
from -• to +6 dB with the front panel level control. All potential
overload points of each channel are continuously monitored by an
extremely fast “peak” overload detector, followed by a “peak-
stretching” circuit for clear indication of overload conditions. The
detector thresholds are chosen for approximately 2 dB headroom
when the overload led illuminates, giving the user the ability to
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Performance Highlights
PE232MKII
•2 x 30 band constant Q precision DLT graphic equaliser.
•2 x 2 band constant Q parametric equaliser/notch filter.
•Variable HP filter.
•Graphic equaliser 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.
•Fail safe 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
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This manual suits for next models
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Table of contents
