Universal Audio 533 User manual

BEFORE PROCEEDING WITH COMPLETE UNPACKING AND SETUP
PLEASE READ THE SECTION ON UNPACKING AND INSPECTION
model 533
GRAPHIC EQUALIZER
model 535
DUAL GRAPHIC EQUALIZER
Mhd
UREI Incorporated
8400 BALBOA BOULEVARD
NORTHRIDGE, CA. 91325-4100 U.S.A.
PHONE: (818) 895-UREI (895-8734)
FAX: [phone]
© Copyright 1979, 1988 UREI Incorporated

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TABLE OF CONTENTS
PAGE
SECTION I. INTRODUCTION
1.1 DESCRIPTION 1
1.2 SPECIFICATIONS 2
1.3 CONTROLS 3
SECTION II. INSPECTION AND INSTALLATION
2.1 UNPACKING AND INSPECTION 4
2.2 ENVIRONMENTAL CONSIDERATIONS 4
2.3 POWERING 4
2.4 LINE VOLTAGE SWITCH 5
2.5 EXTERNAL CONNECTIONS 5
2.5.1 MODEL 301 XLR/QG ADAPTER 6A
2.6 IMPEDANCE AND TERMINATION 7
2.7 SIGNAL LEVEL AND OVERLOAD DETECTOR 8
2.8 ACCESSORIES 8
2.9 RACK MOUNTING A MODEL 533 8
2.10 RACK MOUNTING TWO UNITS (MODEL 533) 9
SECTION III. OPERATING INSTRUCTIONS
3.1 GENERAL 11
3.2 SYSTEM CHECK 11
3.3 EXPERIMENTATION 11
3.4 DOCUMENTATION 11
3.5 APPLICATION 11
3.5.1 OBJECTIVE MEASUREMENTS VS SUBJECTIVE HEARING 13
3.5.2 ADDITIONAL HINTS 13
3.5.3 SPECTRAL DISTRIBUTION IN THE AUDIO SIGNAL 14
3.5.4 EQ SYSTEMS AND LIMITERS 14
3.6 DISCUSSION OF EQUALIZATION 15
3.6.1 BEFORE EQUALIZATION 17
3.6.2 MEASUREMENT TECHNIQUES 18
3.6.3 ADJUSTMENT OF EQUALIZERS 19
3.6.4 SOME PROBLEMS WITH CORRECTIVE ROOM EQ 19
3.6.5 FEEDBACK SUPPRESSION 20
3.7 GAIN STRUCTURE AND SIGNAL-TO-NOISE 21
3.8 INPUT LEVEL 22
3.9 OVERLOAD INDICATOR 22
SECTION IV. THEORY OF OPERATION
4.1 GENERAL
4.2 INPUT AMPLIFIER
4.3 GAIN AMPLIFIER
4.4 GRAPHIC EQUALIZER
4.4.1 GENERAL
4.4.2 FILTERS
2323
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23
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TABLE OF CONTENTS (Continued)
4.4.3 THE ACTIVE INDUCTOR
4.5 OUTPUT AMPLIFIER
4.6 OVERLOAD INDICATOR
4.7 POWER SUPPLY
PAGE
25
26
26
26
SECTION V. MAINTENANCE
5.1 GENERAL 27
5.2 REPAIRS AND WARRANTY 27
5.3 SERVICE ADJUSTMENTS 27
5.3.1 COMMON MODE BALANCE 27
5.3.2 OFFSET ADJUSTMENT 28
5.4 CLEANING 28
5.5 ON OP AMPS 29
SECTION VI. ILLUSTRATION
SCHEMATIC DIAGRAM OF UREI MODEL 533
SCHEMATIC DIAGRAM OF UREI MODEL 535

SECTION I
INTRODUCTION
FIGURE 1. MODEL 535 FRONT PANEL.
NOTE: This manual contains complete instructions for the operation
of the two-channel "Dual Graphic Equalizer" Model 535.
However, this manual is also intended for the single channel
"Graphic Equalizer" Model 533. If used with a Model 533, all
references to the two-channel unit should be disregarded.
1.1 DESCRIPTION
The Model 535 Dual Graphic Equalizer is a studio quality
product which has wide application in recording, sound reinforcement,
radio and TV production, and high fidelity music systems.
The system is designed to operate at any nominal level from as
low as -20 dB (Ref. 0.775 V) allowing its use with low level
mixers, high or low impedances, and balanced or single-ended
circuits. The Model 535 provides 12 dB of boost or cut at each of
its 10 frequencies which are centered at ISO 1 -octave increments
from 31.5 Hz to 16 kHz. The positions of the control arms of the
vertical, stepless controls provide a graphic representation of the
response curve selected.
The filters are active, minimum phase, 2 -pole synthesized LC
networks, whose skirts properly combine for minimum ripple and
phase shift when used in combination. A front panel control
adjusts the gain from -10 dB to +20 dB. Bypass switches permit
switching the equalization out for A-B tests. An optional (SC -1)
security cover may be installed to protect all operating controls
against inadvertent disturbance or tampering in fixed installations.
-1-

1.2 SPECIFICATIONS
ELECTRICAL (EACH CHANNEL):
INPUT: Balanced
INPUT IMPEDANCE:
MAXIMUM INPUT LEVEL:
EQUIVALENT INPUT NOISE:
GAIN:
FREQUENCY RESPONSE:
OUTPUT:
OUTPUT LOAD:
POWER OUTPUT:
DISTORTION:
FILTER TYPE:
FILTER BANDWIDTH:
CENTER FREQUENCIES:
FREQUENCY ACCURACY:
RANGE OF BOOST AND CUT:
CALIBRATION OF BOOST
AND CUT:
bridging, differential amplifier.
40 kohms, used as balanced input.
20 kohms, used as unbalanced
(single-ended) input.
+20 dB (7.75 volts).
Less than -90 dBm. 15.7 kHz noise bandwidth
with all controls set flat, output termina-
ted with 600 ohm load (Model 535, -88 dBm).
Variable, -10 dB to +20 dB, with front
panel control.
+1 äuß 20-20,00n Hz (with no EQ).
Floating, transformer isolated.
150 ohms or greater.
+24 dBm into 600 ohm load (12.28 volts),
+20 dB into 150 ohm load (7.75 volts).
Less than 0.25% THD, 30 Hz to 15 kHz at
maximum rated output.
2 -pole synthesized L -C.
1 -octave at -3 dB points with 8 dB
boost or cut.
Standard ISO (Hz) 31.5 63 125 250 500
lk 2k 4k 8k 16k.
±3% of center frequency.
12 dB, single filter section.
Within 1 dB of indicated setting, 0 to
±6 dB, within 1.5 dB of indicated
setting, ±6 to ±12 dB, (single
filter section).
CHANNEL SEPARATION: 60 dB worst case at high frequencies,
typically better than 80 dB.
1MlISCELLANEOUS:
POWER REQUIREMENTS: 100-125 VAC or 200-250 VAC, 50/60 Hz,
switch selectable, less than 10 W.
-2-

ENVI RONMENT :
CONNECTIONS:
Operating 0°C to +50°C (+32°F to +122°F);
storage -20°C to +60°C (-4°F to +140°F).
Input and output, through rear chassis
barrier strip, or XLR/QG connectors
through Model 301 accessory adapter;
Power through 3 -wire power cable;
Model 533 utilizes IEC style connector
and power cord. (See Installation
Instructions, Section 2.5.)
PHYSICAL CHARACTERISTICS:
DIMENSIONS: Model 535, 483 x 89 mm rack panel; depth
behind panel 203 mm. (19" x 3-1/2" x 8");
Model 533, 216 x 89 mm rack panel; depth
behind panel 190 mm (8-1/2" x 3-1/2" x
7-1/2").
FINISH: Panel is 3.18 mm (1/8") brushed clear
anodized aluminum, in two shades.
Chassis is cadmium plated steel.
WEIGHT: Model 535, 4.31 kg (9.5 pounds);
Model 533, 2.95 kg (6.5 pounds).
SHIPPING WEIGHT: Model 535, 6.35 kg (14 pounds);
Model 533, 4.08 kg (9 pounds).
ACCESSORIES: Model SC-1 Security Cover, smoke gray
transparent plastic; covers all operating
controls (Model 535 only).
1.3 CONTROLS:
EQUALIZATION:
Model 301 XLR/QG adapter; two needed for
Model 535. One adapter provides connec-
tions for signal input and output.
Vertical slide controls, continuously
variable 0 to ±12 dB.
GAIA: Screwdriver adjustable from -10 dB to
+20 dB.
EQ IN/OUT: Front panel toggle switch.
POWER: Front panel toggle switch.
INDICATORS: LED, Power ON;
LED, Overload Condition, levels monitored
at 3 circuit points;
MAINS VOLTAGE: Rear panel slide switch, 115/230 volts.
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SECTION II
INSPECTION AND INSTALLATION
2.1 UNPACKING AND INSPECTION
Your Model 535 was carefully packed at the factory, and the
container was designed to protect the unit from rough handling.
Nevertheless, we recommend careful examination of the shipping
carton and its contents for any sign of physical damage which
could have occurred in transit.
If damage is evident, do not destroy any of the packing mater-
ial or the carton, and immediately notify the carrier of a possible
claim for damage. Shipping claims must be made by the consignee.
The shipment should include:
Model 535 Dual Graphic Equalizer
UREI Instruction Manual (this book)
Two-part Warranty Card bearing the
same serial number as the Model 535.
Mounting screws and finish washers
(for rack mounting of 535 only).
2.2 ENVIRONMENTAL CONSIDERATIONS
The system will operate satisfactorily over a range of ambient
temperatures from 0°C to +50°C (+32°F to 122°F), and up to 80%
relative humidity.
If the system is installed in an equipment rack together with
high heat producing equipment (such as power amplifiers), adequate
ventilation should be provided to prolong the life of components.
Also, while circuitry susceptible to hum pick-up is sufficiently
shielded from moderate electromagnetic fields, installation should
be planned to avoid mounting the system immediately adjacent to
large power transformers, motors, etc.
2.3 POWERING
The 535 may be operated from either 100-125 VAC or 200-250
VAC mains (50 or 60 Hz, single phase.) As indicated in Section
2.4, the nominal line voltage may be selected with a rear panel
switch. BE SURE TO VERIFY BOTH THE ACTUAL LINE VOLTAGE, AND THE
SETTING OF THE VOLTAGE SELECTOR SWITCH BEFORE CONNECTING THE
535 TO THE MAINS.
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To comply with most Electrical Codes, the 535 is supplied
with a three-wire AC cord, the grounding pin of which is connected
to the chassis. In some installations this may create ground -loop
problems. Ground loops can become very evident (as hum and buzz)
if a significant potential difference exists between the AC conduit
ground and the grounded metal enclosure in which the chassis is
installed. If hum is experienced, check for the possibility of
ground loops by using a 3 -prong to 2 -prong AC adapter, ungrounding
the AC plug temporarily. This ungrounds the Model 535, and will
probably cure the hum or buzz, but is not a substitute for proper
system grounding. Be aware that unless the Model 535 Dual Graphic
Equalizer is AC grounded, a safety hazard can exist. UREI accepts
no responsibility for legal actions or for direct, incidental or
consequential damages that may result from violation of any
electrical codes.
2.4 LINE VOLTAGE SWITCH
Unless a tag on the line cord specifies otherwise, the
Model 535 was shipped ready for operation with nominal 115 VAC
power mains. In order to change this for nominal 230 V (50 or
60 Hz), slide the VOLTAGE SELECTOR switch on the rear panel to
the 230 position. The voltage is visible in a window next to the
switch slot. Be sure to change the fuse to the correct value:
1/8 -amp slo-blo when changing to 230 V operation or 1/4 -amp
slo-blo for 115 V operation. A small screwdriver should be
used to move the recessed switch.
2.5 EXTERNAL CONNECTIONS
Permanent input and output signal wires should be shielded
cable, and connected in accordance with standard wiring practice,
as indicated on the rear panel barrier strip. If the XLR/QG
connectors are to be used, install the accessory Model 301
according to the instructions suppplied with the adapter.
(See also "Mounting Instructions," page 6A.)
If the Model 535 output is connected to a high impedance
circuit, we recommend shunting the "±" and "COM" output terminals
with a 620 ohm, 1/2 watt resistor. This assures optimum loading
for the 535. (See section 2.6 regarding input termination).
(See Figures 2 and 3 on the following page)
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OUTPUT GRD INPUT
± COM COM ±
10401
OUTPUT / INPUT
/ OPTIONAL
FIGURE 2. CONNECTING THE MODEL 535 WITH BALANCED
INPUT AND BALANCED OUTPUT CIRCUITS.*
OUTPUT GRD INPUT
± COM COM ±
OUTPUT INPUT
FIGURE 3. CONNECTING THE MODEL 535 WITH UNBALANCED
INPUT AND UNBALANCED OUTPUT CIRCUITS.*
*With a balanced input and unbalanced output, or vice-versa,
use the appropriate connections suggested by each of the above
diagrams. No special switching or transformers are needed.
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