Box 500 West Redding, Connecticut 06896 (203) 938-2588~ Specifications Effective July
15,1982
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INTRODUCTION
THE DISPLAY
The Gold Line Digital Model 30 Real Time Analyzer
represents a ground-breaking step forward in the design of
acoustic measurement equipment. While the one-third
octave real time analyzer is not a new concept in itself, the
use of microprocessor technology allows extreme accuracy
stability, and provides a powerful tool at a price below that
of units with far fewer features.
The heart of the Gold Line 30 is a quartz crystal controlled
filtering system called “Switched Capacitive Filtering.’
This system results in filters that never drift in band width,
center frequency, or flatness from filter to filter. Switched
capacitive filters will withstand hard usage, the abuse of
road trips, and will never require calibration due to aging or
temperature problems unlike the inherent changes that take
place with all analog filters. Spectrum analysis is
accomplished by a powerful microprocessor operating at
speeds of better than 6 mega hertz, and processing filter
information at a rate of more than 500 samples per second.
Features: Six (6) memories allow storage of information
from six different locations. Any location or group of
locations can be displayed as an average, or as a weighted
average. A choice of “FLAT” “A’ or a “USER” weighted
curve is available. Extra weighting can be applied to any
location or group of locations for special emphasis. For
special environments or effects, the Soundman, by utilizing
the USER option, can program his own weighted curve,
such as a favorite high frequency roll-off. Gold Line 30
memory features allow sophisticated sound equalization
and reinforcement to be accomplished easily and without
guesswork.
In order to simplify equalization, an “Auto Level” feature
is provided to maintain the LED display normalized about
the “0” line.
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PINK NOISE
The Gold Line 30 incorporates a pseudo randomly
generated pink noise source. This stable display of equal
energy across the entire audio spectrum makes equalization
adjustments far easier. A precise pink noise gating is
provided for future use with RF60 and other gating options.
SOUND PRESSURE
Accurate sound pressure level readings to 129 dB are
displayed on the 3-digit numeric display. FLAT, +A curves
are selectable. An indicator LED under the numeric display
will indicate that the reading is BROADBAND SPL.
A 30-band display matrix of 300 LEDs
Step selectable in 1, 2, or 3 dB increments
A range of: 10, 20, or 30 dB
Peak, monitor and noise integrate time constants
Peak Hold mode
OPTIONS
A primary advantage of the digital RTA is the many
options that can be added for specialty needs. By providing
three expansion ports plus an extra prom location, Gold
Line can offer the user a wide variety of options such as:
RT6O, User Curves, non-volatile memory computer plotter
and CRT interfaces plus special music options. Many
additional options will be made available as the needs
arise.
BASIC INFORMATION
Please read this manual carefully before attempting to use
your RTA! While diving in “blind” is unlikely to be
harmful, the unit demands a fair amount of familiarization
with the concept of keypad control. This method is not yet
widely used on analog test gear, but heralds the future of
such devices.
NOTE: This manual does not contain servicing information.
In order to protect your warranty all servicing should be
referred to your dealer.
THE FRONT PANEL
Please have the unit in front of you, or refer to the
illustration on the following page, as we explain its
features, one at a time, beginning at the far left:
POWER: Tums the unit on and off; the power source can
be either 110/220 VAC 50/60 Hz or DC from optional
rechargeable battery pack. European option designed to
meet VDE specs. On European units a standard IEC socket
is provided in place of line cord. Please note that the basic
unit has no memory “keep-alive” and any information
stored in memory will be lost if power is interrupted for
any reason!
SPECTRAL DISPLAY: The area behind the red bezel
contains a matrix of LEDs 30 columns wide by 10 high.
Each vertical row corresponds to a one-third octave section
of the audio spectrum, located at standard ISO center
frequencies. Each horizontal row represents to a different
level of energy (for each individual band) as determined by
the SCALE setting of the
REF LEVEL
unit, and read off the appropriate dB/STEP column.
(Therefore, the left legend of -6 to +3 dB is for 1 dB steps
while the -12 to +6 dB and -18 to +9 dB scales on the right
indicate 2 and 3 dB steps respectively.)
The display is also used to communicate power-up
calibration and error messages indicating improper entry of
instructions.
STATUS INDICATORS: Behind the remainder of the
bezel, and visible through holes in the panel to the left of the
keypad, are a number of LEDs which report the status of,
and changes in, the unit’s operational mode. We will not
itemize these functions at this point as many are selfexplanatory or will become so as one learns the keypad!
KEYPAD: Unlike conventional analog controlled
instruments which required “knob-twisting;’ all features of
the digital R1A are accessed by pressing buttons on the
keypad. This action, hereafter referred to as a keystroke, will
be called out in the instructions by the printed legend
enclosed in a box, i.e., RTA denotes a single keystroke on
the “RTA” button. Certain keys may have several different
functions depending on the mode of unit operation.
KEYPAD & DISPLAY FUNCTIONS: The digital RTA
has three basic modes of operation: RTA, Memory and
Option. Key assignments will vary from mode to mode, with
the current mode determining their function. The status
LEDs keep track of all operations and referring to them can
avoid confusion in interpreting the display.
(A.) RTA Mode: This is the “normal” mode of unit
operation. The analyzer “powers-up” in RTA when switched
on, and will be used in this mode the majority of the time.
The following conditions exist after the turn-on cycle is
complete (more on this later):
Sca!e=3 dB/STEP
Ref Level = 100 dB SPL at “0” line (with Gold Line Mic)
Weight = Flat
Decay = Slow
Display Mode = Average (Bargraph)
(Operation mode is RTA!)
The appropriate LEDs will illuminate to call out the above. All
parameters may be varied by sequential keystrokes on the keys
as follows:
SCALE - Cycles the scale through 1, 2 or 3 dB/STEP
WEIGHT - Selects FLAT or “A” weighting (an optional user
curve is available).
DECAY - Se1ects slow, medium or fast decay of the spectral
display to accommodate different measurement situations.
Slow - approximately 3.5 dB/sec. Medium - approximately 7
dB/sec. Fast - approximately 21 dB/sec.
AVG and PEAK - Allow selection of either average or peak
display mode for equalization and/or program analysis. AVG
displays in vertical bars and PEAK via dots on the spectral display Overrange in AVG is indicated by the bottom LED in a
column extinguishing, while overrange in PEAK is evidenced
by appearance of a second LED below a dot on the top row of
the display.
PK-HD (Peak Hold) - Allows infinite retention of momentary
program peaks via dots frozen above either the AVG or PEAK
readout. Unlike AVG and PEAK, this is a push-on, push-off
keystroke that can be added to either mode.
(B.) Memory Mode: Provides a means of storing and retrieving a complete map of all front panel display parameters,
including status indicators. While display of memory must be
accessed from RTA mode, store may be invoked from any
operational mode to provide a “snap-shot” of the front panel at
any given instant.
STORE - When this keystroke is performed from RTA, it acts
as a freeze for the display. The frozen image can be placed in
any of all of the six memories by:1 thru 6. RTA will then
return the unit to normal mode. NOTE: Omitting assignment of
a memory allows this to be used as a “hold” function.
Any or all memories may be written over through the above
sequence. From auto-level mode the store key does not act as
a hold, but merely arms the unit for storage of the display via
numeric keys 1-6.
DISP - Blanks the spectral display and enables recall of any
of the six memories by the appropriate numerical keystrokes:
1 – 6 - Selects memory desired.
RTA - Returns the unit to Real Time mode from memory or
option modes. All conditions will be the same as when RTA
was left, except for REF LEVEL. If Auto-Level has been
called. RTA also functions as a reset from an ERROR
indication.
REF LEVEL - Raises or lowers the reference SPL by the
dB/STEP quantity chosen. (1, 2 or 3 dB/STEPS).
(C.) Optional Modes: All optional modes must be
addressed from RTA mode. All are accessed by first
pressing the OPTION key and then the appropriate option
numbers by following the keystroke sequences listed below:
OPTION (#) 1 SUM
OPTION (#) 3 AUTO
OPTION (#) 4 BROADBAND SPL
OPTION (#) 7 PINK NOISE
OPTION (#) 9 CALIBRATE
Option #1- SUM: This mode allows arithmetical summing
of any or all response curves stored in memory provided that
SCALE, WEIGHT, and Display Mode’s do not differ and
that PK-I-ID was not in use on any of them. Any attempt at
summing non-compatible curves will yield an ERROR
indication, with the offending status LED5 flashing to
indicate the area of conflict. Keystrokes are:
OPTION - Enables optional key function (Option LED will
come on).
1 - Calls summing mode and blanks screen.
1 – 6 - Inputs desired memories. These are displayed as they
are entered and may be inputted more than once for weight ing the summation (a maximum of 10 memory entries per
summation). The ability for the user to weight the average
according to his own priorities for each situation guarantees
that the resulting average will be in accord with the user’s
perception of the problem.
OPTION - Displays sum of all selected memories with correct adjusted reference level. This sum may be written into
memory (or overwritten) by:
STORE - Enables memory.
1 - 6 - Places it in desired location.
RTA - Returns unit to RTA mode.
Option #3 -AUTO: Auto-Level lets the unit hunt for the
correct reference level by updating the spectral display and
level readout twice per second until the average height of all
LEDs is located on the “0” line. Increments of level change
will be per SCALE setting.
OPTION - Enables option mode.
3 - The display will strobe every half-second looking for the
correct reference level. When the readout has stabilized onscreen,
RTA - Returns unit to RTA and locks REF LEVEL.
Again, note that STORE will function from Auto-Level mode!
Option #4—BROADBAND SPL:
OPTION - Enables option mode.
4 - The spectral display will blank and the broadband detector
circuitry will update every ½ second and indicate True
Broadband Sound Pressure Level in the 3-digit window.
Option #7—PINK NOISE: Pink Noise output may be
switched on and off as follows:
OPTION – Enables option mode.
7 - Turns on noise output and automatically falls back to RTA
mode. Repeating, the above sequence will turn off the noise
source.
Option #9—CALIBRATE: This function, part of the unit’s
normal power-up procedure, examines the 30 filter outputs for
any DC offset and compensates for it in software. If the RTA
is in continuous use for any length of time it may be advisable
to recalibrate it by:
OPTION - Enab1es option mode.
9 - Runs auto-cal and automatically falls back to RTA.
INPUTS: Microphone input to the analyzer is made via the
female XLR connector to the right of the keypad. The RTA
will accept a signal from any low Z balanced microphone of
the type used for pink noise analysis and has DC voltage for
remote “phantom” powering of condenser microphones. We
suggest Gold Line’s MK-30 or AKG 451 E Series.
Line Level hi-Z sources such as tape recorder or mixer outputs may be connected to the 1/4” phone jack above the mic
input. Use of the line input will disable the mic input however.
Units can be ordered with mic and line inputs on rear with
front panel switch to control both functions.
THE BACK PANEL
PINK-NOISE OUTPUT: Broadband pink noise at a nominal
700mv. RMS is provided from this unbalanced output for feed
to the device or system under measurement. The noise source
is switched on or off by keypad control, but its level is fixed
and must be adjusted at the unit being driven.
BATTERY PACK: The optional rechargeable battery pack is
connected to the RTA via the 9-pin Molex connector to the
right of the pink noise output.
BATT-AC: This switch selects power source as required.
HEAT - SINK: The finned heat-sink dissipates considerable
thermal energy from the unit’s power supply and may become
quite warm after extended use. Make sure that sufficient ventilation is allowed and never place anything over the fins, or
the holes on top of the unit.
SOME THEORY: Traditionally, real-time equalization is performed by feeding a pink noise signal through the system to be
adjusted, setting up a calibrated mic in the sound-field of the
loudspeakers, and observing the mic’s output on a one-third
octave analyzer. The system equalizer is then adjusted until
an acceptably smooth speaker-room response has been
obtained.
The above procedure can be tedious and lengthy (undesirable in most real-world situations), and yields the desired
response only of the measurement position, which may not
be typical of the entire room (i.e. near an absorptive surface
or in a standing-wave null). In other words, the traditional
procedure does not address the need for knowing the overall
power response throughout the room; to do so would involve
a composite of many response curves taken at various positions (and corrected for different sound pressure levels!).
The Digital RTA, through the use of its unique features, can
enable a speedy determination of the average room response,
so a very educated setting of the system equalizer can be
made.
CONNECT THE UNIT AS FOLLOWS:
1. The pink noise output of the R1A should run into a line
input of the sound system, and must be ahead of the equalizer. If it is connected to a channel of a console, insure that
the tone-controls are centered or bypassed, and center all
equalizer sections.
2. Connect a calibrated microphone (Gold Line MK30) to
the mic input on the front panel of the RTA.
TO PERFORM A TYPICAL ANALYSIS:
1. - Switch the RTA “on’ Initially, the entire front panel will
illuminate. Next the spectral display will spell out “AUTO,”
“CAL:’ and “READY” in sequence, before dropping into
RTA mode with the earlier described conditions present.
2. - Making sure sound system gain is at minimum, activate
the pink noise OPTION 7.
3. - Carefully increase sound system gain until the noise
signal is well above ambient sound in the room.
4. - Call Auto-Level OPTION 3.
5. - When the display has stabilized, return to RTA RTA.
6. - Store the response curve in memory #1 STORE 1.
7. - Return to RTA RTA and repeat steps 4 through 6 up to
five more locations throughout the room, storing the results
in the remaining memories.
If the level throughout the room is consistent enough to keep
the responses on-screen, it may be faster to omit Auto-Level.
(Conversely, if it varies widely, leave the unit in Auto-Level
and store directly from this mode [upon stabilization.)
8. - When all memories are full (or as many as you wish to
consider) disable the pink noise OPTION 7.
9. - Sum all memories you have filled OPTION 1 plus
memories 1 – 6 OPTION . If you want to give extra
significance to any locations, you can apply extra keystrokes
to these locations.
For example: OPTION 1 1 2 2 2 3 6 6 6 OPTION
In this example the user has selected Option 1 which is the
summing mode. He increased the significance of area #2 by
three times and the significance of area #6 by three times.
All other locations he has valued at a keystroke of one. Note
user chose not to sum locations #4 and #5. In both examples
you will have a composite response readout of the room.
Store the composite in an available memory for later reference
STORE plus a memory number.
10. - The system equalizer can now be adjusted for the inverse
of room response. This is your initial setting, which may be
adequate; however, for greater accuracy you can proceed as
follows:
11. - Increase the resolution of the analyzer to 1 dB/STEP
SCALE and repeat steps 2 thru 9. Do not write over the memory where you have stored the previous sum. Store your new
sum and return to RTA RTA.
12. - View the two sums in turn. If more correction is needed,
adjust the equalizer accordingly, allowing the higher definition
of the spectral display. It should be noted that different rooms
will sound better when the Soundman applies his own curve.
Flat is the necessary first step for the Soundman. By making
use of the information provided by his analyzer he can fine
tune his EQ to a curve that complements the performance. This
completes the equalization process.
FEEDBACK CONTROL (Ring Modes): In order to monitor
for feedback during a live performance, the analyzer should be
set to a reference level that keeps most of the LEDs toward the
bottom of the display. Set the unit for PEAK - with a SCALE
setting in 3 dB steps and Slow DECAY Time. The soundman
will now be able to see any ring modes and adjust his EQ by
cutting only the offending frequency. This procedure will
allow frequency control with a minimum impact on the music.
SPECIFICATIONS
MICROPHONE:
A low impedance balanced microphone input is provided via a
3.pin XLR socket on the front panel. Phantom power is
available at this socket and the Gold Line 30 will operate with
F.E.T microphones such as the AKG 451E series or Gold
Line’s MK3O.
MICROPHONE INPUT:
Balanced differential XLR input
12 VDC phantom powering. 600 Ohm input impedance
LINE INPUT:
Single ended ¼” input overrides microphone input 10 Ohms
input impedance
REFERENCE LEVEL SETTINGS:
A choice of 1, 2, or 3 dB steps. Increments from 50 to 129 dB
SPECIAL CONDITIONING:
Microprocessor controlled A/D converter
Dynamic range of 48 dB. Accuracy of ±.18 dB
FILTERS:
30 frequency bands on I.S.O. Centers of ±1%
Relative flatness: ±.5 dB
Stability quartz crystal controlled ±.005 %
WARRANTY: The GOLD LINE 30 is warranted to the
original purchaser against defects in workmanship and material
used in manufacture for a period of one year from the date of
purchase. Faults due to purchaser misuse, unauthorized
modifications or accidents are not covered by this warranty.
No other warranty is expressed or implied.