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Professional Audio Products Data Sheet
GQ Series Interpolating Constant-Q Equalizer
GQ 15 & 30
GRAPHIC EQUALIZERS
General Description
The Rane GQ Series Interpolating Constant-Q Equalizers
consist of the GQ 15, a two-channel, 2/3-octave design and
the GQ 30, a one-channel, 1/3-octave version. Housed in a
two rack-space unit, these units feature long throw 45mm
sliders for excellent resolution of settings, as well as adjustable bandlimiting Low and High Cut Filters.
The active filter sections of these units feature Ranes
patented (#4,891,841) constant bandwidth (constant-Q)
design. The bandwidth of each individual filter is guaranteed
to be narrow enough to prevent unwarranted interaction
between filters, yet wide enough to produce the optimum type
of correction curve demanded by the the most unusual
acoustic surrounding. This differs dramatically from conventional designs of the past. Earlier designs are encumbered
with the unfortunate characteristic of changing bandwidth
with changing boost/cut amounts.
The GQs, aside from being constant-Q devices, also
Features
INTERPOLATING CONSTANT-Q DESIGN
ADJUSTABLE LOW & HIGH CUT FILTERS
TERMINAL STRIP, 3-PIN, & ¼" TRS BALANCED
INPUTS AND OUTPUTS
GROUNDED CENTER DETENTS
INDEPENDENT INPUT AND OUTPUT LEVEL
CONTROLS
provide what Rane has dubbed Interpolating performance.
This means that when two adjacent bands are boosted or cut
to the same level, the response of the equalizer peaks (or
interpolates a response) at a frequency centered between the
filters. Interpolating performance allows effective control
between ISO centers.
Front panel controls and indicators include an input and
output gain control as well as individual overload indicators.
The rear of the unit provides balanced 3-pin input and output
connectors; a ¼" balanced Tip-Ring-Sleeve connector for the
same, and a barrier strip which provides access to all of the
above. This full range of connectors also allows unbalanced
operation by using only the positive and signal ground
conductors of any of the Inputs or Outputs. Included also are
¼" Tip-Ring-Sleeve Patch I/O jacks. These allow connecting
to conventional tip-send ring-return insert points on mixing
consoles using only a single ¼" TRS cable.
INDIVIDUAL BYPASS SWITCHES WITH LED
INDICATORS
OVERLOAD INDICATORS
RFI FILTERS
CLASS 2 POWER - AGENCY EXEMPT
UL LISTED POWER SUPPLY
U.S. PATENT 4,891,841
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GQ 15 & GQ 30
Professional Audio Products Data Sheet
GRAPHIC EQUALIZERS
Parameter Specification Limit Units Conditions/Comments
Equalizer:
..........Bands: GQ 15 (15) 2/3-Octave ISO Spacing From 25Hz to 16kHz
...................... GQ 30 (30) 1/3-Octave Iso Spacing From 25Hz to 20kHz
..........Type Interpolating Constant-Q Smooth Combining
..........Accuracy 3 % Center Frequency
..........Travel 45 mm Positive Grounded Center Detent
Inputs: Type Active Balanced/Unbalanced
..........Connectors Term, 3-Pin & + ¼" TRS•••
..........Impedance 40k 1% Ohms Balanced: 20k Ohms/leg
..........Maximum Level +21 1 dBu
Outputs: Type Active Balanced
..........Connectors Term, 3-Pin & + ¼" TRS•••
..........Impedance 100 1% Ohms Each Output
..........Maximum Level +27 ³ 2k•; +24 ³ 600• 1 dBu
Overall Input Gain Range -12 to +12 1 dB
Overall Output Gain Range +12 to -12 1 dB
Adjustable Low Cut Filter 10Hz-250Hz, 12dB/Oct 10% Hz
Adjustable High Cut Filter 3.1kHz-40kHz, 12dB/Oct 10% Hz
RFI Filters Yes
Passive Bypass Switches Yes LED Indicated
LED Thresholds: Overload +18 1 dBu Output or any Internal Level
Frequency Response 10-40kHz 10 % -3dB Points
THD+Noise 0.009 .002 % +4dBu, 20-20kHz
IM Distortion (SMPTE) 0.005 .003 % 60Hz/7kHz, 4:1, +4dBu
Signal-to-Noise Ratio re +20dBu/+4dBu 20kHz Noise BW; Balanced
108/92 2 dB Sliders Flat, Gains Up (Unity)
91/75 2 dB Full Boost, Gains Up (Unity)
106/90 2 dB Full Cut, Gains Up (Unity)
Channel Separation (GQ 15) 70 5 dB 20-20kHz
Maximum Current 400 mA RMS Current From Remote Supply
Power Supply Input 18-24VAC w/center tap 10% Vrms
Power Supply Connector 6-Pin Mod Plug
Safety Agency—Unit
..........Classification Class 2 Equipment National Electrical Code
..........Design Safety Extra-Low Voltage VDE SELV
..........U.L. Listing UL 813 Exempt Class 2
..........C.S.A. Certification C22.2 No. 1 Exempt Class 2
..........CENELEC IEC 65 Exempt Harmonization Doc. HD 195.S4
Remote Power Supply Model RS 1 Class 2 Equipment
..........U.L. Listed E90493
..........C.S.A. Certified LR62694
..........230VAC Export Model Meets requirements of IEC 380 Double Insulated Design
Unit: Construction All Steel
..........Size 3.5"H x 19"W x 8.5"D (2U) (8.9cm x 48.3cm x 21.6cm)
..........Weight 7 lb (3.2 kg)
Shipping: Size 7" x 22" x 13" (18cm x 56cm x 33cm)
..........Weight (GQ 15) 12 lb (5.4 kg)
..........Weight (GQ 30) 12 lb (5.4 kg)
Note: 0dBu=0.775Vrms
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Block Diagram
Professional Audio Products Data Sheet
GQ 15 & 30
GRAPHIC EQUALIZERS
Application Information
Constant-Q graphic equalizers arose from the sound
professionals need for greater control with less interaction
than previously possible with conventional equalizers. Truth
in slider position became a requirement. The curve traced out
by the slider positions on constant-Q designs indeed represents the actual changes to the frequency response. On
conventional designs they do not. Combine this feat with the
Rane developed interpolating characteristic and you have a
tool without peer.
The GQ series of products from Rane goes one step
further toward being the best device for any application. It
offers choice of all common audio connectors. The inclusion
of 3-pin, ¼" and terminal strip Input and Output terminals
ensures the GQ 15 ideally suits all possible situations.
Independent INPUT and OUTPUT GAIN controls allow
maximum flexibility in setting up your gain structure.
Operating both sliders together always yields unity gain
through the equalizer. Always operate the unit with both
GAIN controls as far towards the top of the unit as possible
without lighting the OL indicators. Only in situations where
input overloads become a problem should the GAIN controls
be moved downward. This yields the best noise performance.
The HIGH and LOW CUT FILTERS allow bandlimiting
of a system. In their full down positions, the bandwidth of the
unit is flat from 20Hz to 20kHz. Any upward movement of
either slider begins restricting the bandwidth and may aid in
preventing accidental overloads in systems not specifically
designed to handle audio extremes. This is a useful feature in
noise masking and paging systems where full range speakers
are not used. Bandlimiting helps prevent low frequencies
from overloading the speakers.
While designed primarily for permanently installed
systems, this does not mean that its mechanical integrity is
inferior to other Rane products. All Rane signal processing
gear can withstand the rigors of being thrown into the back of
a 68 Pontiac station wagon by their line cords and transported from one bar to another.
CONSTANT-Q DETAILS
Traditional equalizer designs present a problem in that the
filters level control is actually a part of the filter. Consequently, whenever the slider is moved, the bandwidth
changes. The output exhibits the desired bandwidth only at
full boost or cut. It degrades to as much as two octaves at
moderate slider settings. Responding to this dilemma, Rane
developed a topology ensuring constant filter bandwidth
(Q) at all slider positions.
Another important advantage of constant bandwidth is
reduction of adjacent filter overlap. Conventional designs
exhibit excessive overlap at moderate slider settings. Adjusting one slider affects the adjacent neighbors, requiring
readjustments to each. Filter overlap in Rane equalizers is
dramatically less, reducing the need for constant readjustment
of adjacent sliders. This means more effective equalization in
significantly less time.
INTERPOLATING DETAILS
Todays sophisticated acoustic measurement tools show
exact trouble spots. Often these lie between ISO centers. An
interpolating equalizer allows the user to correct for these
response errors by producing a smooth peak or dip between
(i.e., it interpolates, or inserts between) any two adjacent
frequency sliders when they are raised or lowered the same
amount. Non-interpolating responses exhibit a slight dip
(ripple) under similar conditions.
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GQ 15 & GQ 30
GRAPHIC EQUALIZERS
Rear Panel
Professional Audio Products Data Sheet
Architectural Specifications
The graphic equalizer shall be of constant-Q design to
minimize interactions between adjacent bands, and contain
adjustable sliders located on standard ISO center frequencies.
Each band shall have a bandwidth of 1/3 or 2/3-octave, as
specified elsewhere. Sweepable low and high cut filters shall
be provided. A detented and positively grounded 0dB point
shall be provided on 45mm linear sliders with dust dams.
An input and output gain control shall be provided, each
covering a range of -12dB to +12dB with a center detent at
0dB. These controls shall be of the vertical slide variety.
The inputs shall be active balanced/unbalanced designs
terminated with 3-pin, ¼" TRS (tip-ring-sleeve) and barrier
strip connectors. The outputs shall be fully balanced and
terminated with 3-pin, ¼" and barrier strip connectors. Each
unit shall also provide a ¼" tip-ring-sleeve Patch I/O connector. RFI filters shall be provided. The unit shall provide a
passive bypass feature requiring no power to operate. When
power is applied to the unit and bypass mode is selected, this
shall be indicated via a red LED indicator. LEDs shall be
provided to indicate Overload conditions on each channel.
The unit shall be powered from a UL listed external AC
power supply. This external supply shall be provided with
each unit and be available with either a 120VAC or a
230VAC primary. The unit shall be entirely constructed from
cold-rolled steel.
The unit shall be a Rane Corporation GQ Series Equalizer.
Available Accessories
SC 3.5 Security Cover
References
1. D. Bohn, Constant-Q Graphic Equalizers, Rane Note 101, (1982).
2. D. Bohn, A New Generation of Filters, Sound and Video Contractor, vol. 2, pp. 36-39 (Feb. 1984).
3. T. Pennington, Constant-Q, Studio Sound, vol.27, pp. 82-85 (Oct. 1985).
4. D. Bohn, Constant-Q Graphic Equalizers, J. Audio Eng. Soc., vol. 34, pp. 611-626 (September 1986).
5. D. Bohn, Exposing Equalizer Mythology, Rane Note 115, (1986).
6. D. Bohn, RAP - Remote AC Power: An Idea Long Overdue, Rane Note 121, (1989).
7. D. Bohn, Operator Adjustable Equalizers: An Overview, Rane Note 122, (1990).
©Rane Corporation, 10802 47th Avenue W., Mukilteo WA 98275-5098 TEL(206) 355-6000 FAX(206) 347-7757
All features & specifications subject to change without notice. 520-152 APR94Printed in the U.S.A. on Recycled Paper
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