Radica Games DAVID-II 716 Operating And Maintenance Instruction Manual
OPERATING AND MAINTENANCE
INSTRUCTION MANUAL
“DAVID-II”
——— MODEL 716 ———
FM-STEREO PROCESSOR / GENERATOR
__________
—– USER’S RECORD —–
Model 716 - Serial No. _______
Date Purchased _____________
Warranty Card Mailed — ¨
OPERATING AND MAINTENANCE
INSTRUCTION MANUAL
DAVID-II
—–—— MODEL 716 ———–
FM-STEREO PROCESSOR / GENERATOR
October, 1995
1305 Fair Avenue, Santa Cruz, CA 95060
TEL: (408) 458-0552 – FAX: (408) 458-0554
1
TABLE OF CONTENTS
Section I - INTRODUCTION
Model 716 Product Description ........................................................................................... 3
General - Features
Model 716 Technical Specifications..................................................................................... 3
Patent Notice ........................................................................................................................ 4
Block Diagram ...................................................................................................................... 5
Section II - Installation
Unpacking and Inspection ................................................................................................... 6
Mounting ............................................................................................................................... 6
Rack Requirements - Heat Dissipation
AC (Mains) Power ................................................................................................................. 6
As Delivered - Voltage Selector - Power Cord
Radio Frequency Interference (RFI) ....................................................................................7
Location - Ground Loops
Line Input and Input Range Selection ................................................................................. 7
Input Connections - Balanced Inputs - Unbalanced Inputs -
Input Gain Range - Gain Jumpers
Pre-Emphasis Selection ....................................................................................................... 9
“Bass-Enhance” Equalization .............................................................................................. 9
“Bass-Enhance” Jumpering
Subcarrier Input...................................................................................................................11
Composite Output ..............................................................................................................11
Output Ground Loops
Section III - Setup and Operation
Panel Controls and Indicators ........................................................................................... 12
(All Controls and Indicators Defined According to Function)
Normal Setup Procedure ....................................................................................................15
Input Gain Calibration - Output Level Adjustment
Average Compression Adjustment ....................................................................................17
Composite Processing .......................................................................................................17
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Section IV - Calibration
Calibration ..........................................................................................................................18
Equipment Required - Power Supply Check - Clock Set Low-Pass Filter Matching - Crosstalk Trim - Separation Trim
Section V - Circuit Descriptions
Circuit Descriptions ............................................................................................................23
Component Annotation - A PWM Primer - PWM Ramp
Circuitry - Signal Path Circuitry - Input Stages - AGC Stage Wideband Compression and Limiting - High Frequency
Limiter - Filter Overshoot Compensator - Low-Pass Filter Pilot and Subcarrier Generation - Power Supply
Section VI - Appendix
Parts Lists - Schematics - Warranty ..............................................................................35
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Section I
INTRODUCTION
MODEL 716 PRODUCT DESCRIPTION
General Inovonics introduced the first “DAVID” (as in David vs. Goliath) FM-
Stereo Processor/Generator in 1992. The original Model 715 was the
hallmark of simplicity, and was intended to answer the more basic of
FM radio broadcasting needs.
The “DAVID-II,” Model 716, includes a redesigned pulse-widthmodulation audio processing section. This improved processing
circuitry extends the applicability of the DAVID-II into broadcast
environments where perceived loudness and modulation density are
considered germane to the broadcaster’s success.
Features Features of the Inovonics DAVID-II include:
• Comprehensive stereo audio processing: slow, “gainriding” AGC — Wideband Compression and Peak
Limiting — Independent High Frequency Limiting.
• Exclusive “Bass Enhance” equalizer (defeatable).
• Extended-response low-pass filtering with proprietary
overshoot compensation.
• Digital synthesis of pilot and subcarrier for unexcelled
performance and freedom from drift and routine
adjustment.
• Internal combining for RDS or SCA subcarriers.
• Built-in, adjustable Composite Processor.
MODEL 716 TECHNICAL SPECIFICATIONS
Frequency Response (through
appropriate de-emphasis network):
±0.5dB, 20Hz–15kHz; –1dB or
less at 16kHz, –60dB or better at
19kHz.
Stereo Separation (LàR or RàL):
Processing OUT: >65dB,
20Hz–16kHz.
Processing IN: >60dB,
20Hz–16kHz.
Distortion (with full Compression,
1dB below 100% modulation):
<0.25% THD in demodulated
audio above 200Hz.
Noise:
Better than 80dB below 100%
modulation in demodulated audio,
20Hz–16kHz. 38kHz residual and
“digital” noise above 54kHz,
–70dB or better.
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Crosstalk (MàS or SàM):
Processing OUT: nonlinear
crosstalk –55dB or better.
Processing IN: overall crosstalk
–50dB or better
Stereo Pilot:
19kHz, ±1Hz; injection level
adjustable between 6% and 12%,
relative to 100% modulation.
Program Line Inputs:
Active-balanced/bridging;
accommodate nominal “0VU”
input levels between –15dBu and
+15dBu.
SCA / RDS Input:
10K-ohms, unbalanced; accepts
SCA or RDS subcarrier signal
levels between –20dBu and 0dBu
for nominal 5% to 10% injection.
Pre-emphasis:
Integral with split-band audio
processing. May be jumpered for
75µs or 50µs characteristic.
“Bass-Enhance” Equalizer:
Accentuates “perceived” bass
response at user’s option. (See
Figure 4, Page 10.)
AGC Amplifier:
Slow, 0.5dB/sec. correction for
long-term input level variations;
±10dB capture range.
Compressor/Limiter:
Fast-acting peak limiter with
secondary “platform” time
constant to compress dynamic
range with average-value
weighting. Independent high
frequency limiter conforms to
selected pre-emphasis
characteristic. Subsequent
program signal clipping is
relegated to non-repetitive limiter
overshoots 1ms or less in duration.
Composite (Multiplex) Output:
Adjustable between 1V p-p and
8V p-p; 75-ohm source impedance.
Composite Processor:
Adjustable from 0dB to 3dB
clipping of the 100%-modulated
multiplex waveform prior to pilot
injection.
Digital Synthesis Sampling Rate:
608kHz (16X subcarrier
oversampling).
Power Requirements:
105–130VAC or 210–255VAC,
50/60Hz; 15 watts.
Size and Weight:
1¾”H x 19”W x 7”D (1U);
7lbs (shipping).
BLOCK DIAGRAM
A simplified Block Diagram of the DAVID-II is shown on the facing
page. Generator circuitry is explained in detail under Circuit
Descriptions, Section V, which references Schematic Diagrams found in
the Appendix, Section VI.
PATENT NOTICE
Low-pass filter overshoot compensation circuitry used in the DAVID-II
is protected under U.S. Patent No. 4,737,725.
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Figure 1 - Block Diagram, DAVID-II FM-Stereo Processor/Generator
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INSTALLATION
UNPACKING AND INSPECTION
Immediately upon receipt of the equipment, inspect carefully for any
shipping damage. If damage is suspected, notify the carrier at once,
then contact Inovonics.
It is recommended that the original shipping carton and packing
materials be saved for future reshipment. In the event of return for
Warranty repair, shipping damage sustained as a result of improper
packing for return may invalidate the Warranty!
IT IS VERY IMPORTANT that the Warranty Registration
Card found at the front of this Manual be completed and
returned. Not only does this assure coverage of the
equipment under terms of the Warranty, and provide some
means of trace in the case of lost or stolen gear, but the user
will automatically receive specific SERVICE OR MODIFICATION INSTRUCTIONS should they be issued by Inovonics.
Section II
MOUNTING
Rack
Requirement
Heat Dissipation Consuming no more power than a small child’s night-light, heat
Inovonics’ DAVID-II is packaged to mount in a standard 19-inch
equipment rack and requires only 1¾ inches (1U) of vertical rack
space. The use of plastic “finishing” washers is recommended to
protect the painted finish around the mounting holes.
generated by the DAVID-II is insignificant. The unit is specified for
operation within an ambient temperature range of freezing to 120°F/
50°C. Because adjacent, less efficient equipment may radiate
substantial heat, be sure that the equipment rack has sufficient
ventilation to keep the temperature below the stated maximum.
AC (MAINS) POWER
As Delivered Unless specifically ordered for export shipment, the DAVID-II is set at
the factory for operation from 115V, 50/60Hz AC mains. The rearpanel designation next to the fuseholder will confirm both the mains
voltage selected and the value of the fuse supplied.
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A balanced program audio feed to the DAVID-II will use both the +
and the – terminals, plus the associated G, for each of the two stereo
Voltage Selector A mains voltage selector switch is located beneath the top cover of the
unit, adjacent to the AC mains connector on the circuit board. With
primary AC power disconnected, slide the red actuator with a small
screwdriver so that the proper mains voltage (115 or 230) is visible.
You must always install an appropriate fuse, and should mark the rearpanel voltage/fuse designation. It is factory practice to cross-out the
inappropriate marking with an indelible black marking pen. You can
remove this strikethrough with solvent to redesignate.
BE SURE that the mains voltage selector setting and primary fuse value are appropriate for the mains supply before
plugging the DAVID-II into the wall outlet.
Power Cord The detachable power cord supplied with the DAVID-II is fitted with a
North-American-standard male plug. The individual cord conductors
are supposed to be color-coded in accordance with CEE standards:
BROWN = AC “HOT” BLUE = AC NEUTRAL GRN/YEL = GROUND
If this turns out not to be the case, we offer our apologies (cord vendors
vary) and advise that U.S. color coding applies:
BLACK = AC “HOT” WHITE = AC NEUTRAL GREEN = GROUND
RADIO FREQUENCY INTERFERENCE ( R F I )
Location Although we have anticipated that the DAVID-II may be operated
adjacent to high-power transmitters, you should exercise care in
locating the unit away from abnormally high RF fields.
Ground Loops In some installations a mains frequency or RF ground loop may be
formed between the input or output cable shield grounds and the AC
power cord ground. Use of a “ground-lifting” AC adapter should
remedy the situation, though the chassis ultimately must be returned
to earth ground for safety. Generally, being screwed-down in the
equipment rack will satisfy this requirement.
LINE INPUT AND INPUT RANGE SELECTION
Input
Connections
The DAVID-II has electronically-balanced (transformerless) left and
right channel PROGRAM LINE INPUTS. These are brought out to a
screw-terminal barrier strip on the rear panel and include chassis
ground connections for cable shields. Please note that the screw-
terminal barrier block can be unplugged from the chassis! This makes
connection a bit easier and permits quicker removal of the DAVID-II
from the rack should maintenance ever be required.
Balanced Inputs
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channels. Since these are “bridging” (high impedance) inputs, they
provide no termination for the console or other equipment which feeds
the DAVID-II. Please feel at liberty to connect a 600-ohm resistor
across the input terminals should you feel this really necessary. Most
professional equipment nowadays features low output impedances and
high input impedances. The concept of 600-ohm “line-matching” dates
from the age of transformer coupling and is rooted in the mystique of
telephone practices. More often than not, audio line impedance
matching is poo-pooed by today’s hip broadcasters (you) and
equipment manufacturers (us).
Unbalanced
Inputs
In rare instances the DAVID-II may be fed from “semi-pro” gear with
unbalanced outputs. “Disco” mixers fall into this category and are
perfectly serviceable for installations on a tight budget. In such cases,
the single center conductor of the shielded input lead should be
connected to the + terminal, and the shield to G. In addition, a
jumper wire should be installed between the – terminal and G.
Input Gain
Range
The DAVID-II can accommodate line-level program inputs with a
nominal “Zero-VU” value between –15dBu and +15dBu. This 30dB
range is divided into two 15dB ranges by internal jumpering.
As shipped, the DAVID-II is jumpered for professional level inputs
between 0dBu and +15dBu. Most console and STL receiver outputs
fall into this range, +4dBu, +6dBu and +8dBu being typical levels.
Lower levels, between –15dBu and 0dBu, may be encountered when
interfacing with “semi-pro” gear or with feeds via lossy studiotransmitter telephone line circuits. The extra gain for the low level
range is enabled by changing jumpers beneath the top cover.
Gain Jumpers Under the top cover, and just behind the PROGRAM LINE INPUT
barrier strip, you will find two jumper pin strips, each with a “pushon” jumper. The strips are identified as JMP3 and JMP5 in the circuit
board legend, and each has an H and an L marking to indicate the
proper jumper placement for High level and for Low level inputs,
respectively. Figure 2 illustrates jumpering options.
HIGH LEVEL INPUTS
LOW LEVEL INPUTS
(0dBu to +15dBu)
(–15dBu to 0dBu)
Figure 2 - PROGRAM LINE INPUT Range Selection
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PRE-EMPHASIS SELECTION
The DAVID-II supports the 75-microsecond FM broadcasting preemphasis standard, common to the Western Hemisphere and parts of
the Orient, and the 50-microsecond standard used in Europe and Asia.
Pre-emphasis appropriate to the shipping destination is jumpered at the
factory, but this is easily changed if necessary.
Beneath the top cover, locate the second vertical row of integrated
circuits from the right-hand edge of the chassis. This is the row next to
the one behind the input barrier strip. Between the second and third
ICs from the rear panel are two jumper pin strips, each with a push-on
jumper. These are identified as JMP1 and JMP2 in the circuit board
legend, and each is designated with a 75 and a 50 marking to indicate
proper jumper placement for the 75µs and 50µs pre-emphasis
characteristics. Figure 3 illustrates the jumpering options
75-MICROSECOND 50-MICROSECOND
Figure 3 - Pre-emphasis Jumpering
“BASS-ENHANCE” EQUALIZATION
The DAVID-II incorporates a unique bass-boost equalizer which may be
enabled at the user’s option.
Normal DAVID-II low-end response is flat to within 1dB down to 10Hz.
When the equalizer is jumpered into the circuit, response assumes the
shape graphed in Figure 3 on the next page. The effect of this
equalization is to increase the amount of perceived “bottom end,” while
attenuating much of the sub-audible program energy. Very lowfrequency bass notes are lost in nearly all listening situations, only
serving to sabotage modulation efficiency and program density. Even
the megawatt subwoofers in cars with blacked-out windows don’t
respond to frequencies much below 50Hz; rather, they make a lot of
noise in the rather narrow region between 60Hz and 80Hz.
The few dB of boost just before cutoff more than makes up for any lost
legitimate program bass information. This is analogous to the
Rheinfelder Effect, a phenomenon associated with a novel audio noise-
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reduction technique which employs a similar boost-before-cutoff at the
high-frequency end of the spectrum.
“Bass-Enhance”
Jumpering
Figure 4 - “Bass-Enhance” Equalization Curve
As delivered from the factory, “Bass-Enhance” equalization is defeated.
To enable the “Bass-Enhance” equalizer, remove the top cover and
locate the first vertical row of integrated circuits closest to the righthand side of the chassis, the one just behind the PROGRAM LINE
INPUT barrier strip. Close to the front panel, and just to the right of
the two INPUT GAIN controls, you’ll find two jumper pin strips, each
with a push-on jumper, labeled JMP4 and JMP6. Each strip is marked
with the letters F and B, indicating jumper placement for Flat and
Bass-Enhance, respectively. Figure 5 illustrates the jumpering options.
FLAT RESPONSE “BASS-ENHANCE” RESPONSE
Figure 5 - “Bass-Enhance” Jumpering
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