XTA GQ600 User manual

Contents
Safety Warnings .......................................................... 1..................
Unpacking the GQ600 .................................................... 1
..................
Introduction ............................................................... 2..................
GQ600 Filter Characteristics .............................................. 2..................
1/3 Octave Centre Frequencies ........................................... 4..................
Front Panel Functions ..................................................... 5..................
Rear Panel Functions ..................................................... 6..................
Specifications ............................................................. 7
..................
Operating Notes .......................................................... 8..................
Warranty ................................................................. 9..................

Thanks
Thank you for choosing the XTA GQ600 for your application. Please spare a little time to
digest the contents of this manual (figuratively speaking), so that you obtain the best
possible performance from this unit.
All XTA products are carefully engineered for world class performance and reliability.
If you would like further information on this or any other XTA product, please call us.
We look forward to helping in the near future.
XTA Electronics Ltd.
Safety Warnings
Please note the following information which is provided for your safety:
Check correct operating voltage is set on the power supply before connecting mains
power.
Do not expose this unit to rain or moisture.
Do not expose this unit to excessive heat.
Replace all fuses with correct type only.
Do not remove the covers from this unit. No user serviceable parts inside - refer all
servicing to qualified personnel.
The mains power cord is fitted with a safety earth (ground) connection. Do not operate this
unit with this connection removed.
Unpacking the GQ600
After unpacking the unit please check carefully for damage. If damage is found, please
notify the carrier concerned at once. Any claim must be instigated by you, the consignee.
Please retain all packaging in case of future reshipment.
GQ600 Page 1

Introduction
The GQ600 combines innovative features with impressive specification, to produce a new
level of performance in professional equalisation.
The GQ600 is a precision dual channel 1/3 octave graphic equaliser which provides up to
10dB of boost or cut at 30 centre frequencies between 25Hz and 20kHz. Filter design has
been carefully optimised for good interpolation and improved narrow band performance,
whilst high quality long-throw 45mm sliders are used for better resolution. The GQ600 also
provides excellent noise and distortion performance, with a flat noise figure of better than
-98dBm.
A shelving H.F. Trim section is provided, with adjustable gain and frequency allowing fast
adjustments to be made to overall high frequency response. This obviates the need for
system re-voicing when, for example, changes in humidity or audience size occur.
A sweepable high-pass filter offers turnover frequencies of 10Hz to 150Hz and a fixed
frequency low-pass filter is also provided for increased H.F. driver protection. This filter is
selectable in or out of circuit via jumper links on the main circuit board.
Audio inputs and outputs are provided on lockable XLR 's and 'quick-wire' Klippon
connectors and are fully electronically balanced as standard. Optional transformer balancing
is also available for both inputs and outputs.
Additional features include; relay fail-safe bypass, peak level indicators and optional
perspex security cover.
The GQ600 is sturdily constructed from high quality components and undergoes extensive
testing and quality control procedures including a minimum 48 hours burn-in period prior to
despatch.
GQ600 Filter Characteristics
Frequency response of GQ600 with sliders set "flat" and EQ "in", showing effect of high-pass
and low-pass filters.
LPF in
LPF out
High-pass filter
min mid max
GQ600 Page 2

+3dB
+6dB
+10dB
-3dB
-6dB
-10dB
Response of a single 1/3 octave filter section.
Combining effect with sliders set to achieve +10dB overall gain. Note lack of amplitude
ripple.
Freq. min
Freq. max
Response of H.F. Trim frequency control. At maximum and minimum gain.
GQ600 Page 3

Gain max
Gain min
Effect of H.F. trim gain control, with frequency set at minimum.
1/3 Octave Centre Frequencies
The 1/3 octave ISO centre frequencies used on most graphic equalisers are normally
'rounded off' to whole numbers. This leads to unequal spacing of filters if these marked
frequencies are used to calculate filter values.
The GQ600 uses true 1/3 octave frequencies based on 1kHz as a reference, and each filter
is automatically tested and adjusted when required, to achieve a centre frequency accuracy
of within ±3% of these true 1/3 octave frequencies. These are as follows:-
Marked True Marked True Marked True
25 24.80 250 250 2k5 2k52
31 31.25 315 315 3k15 3k175
40 39.38 400 396.7 4k 4k
50 49.61 500 500 5k 5k04
63 62.5 630 630 6k3 6k35
80 78.75 800 793.7 8k 8k
100 99.21 1k 1k 10k 10k08
125 125 1k25 1k26 12k5 12k70
160 157.5 1k6 1k587 16k 16k
200 198.4 2k 2k 20k 20k16
GQ600 Page 4

Front Panel Functions
1.Output Gain Control - allows ±10dB of gain to be applied. This control features a
centre detent for 0dB gain.
2.E.Q. In/Out Switch - selects graphic equaliser filter section in or out of circuit.
3.H.F. Trim Switch. - selects H.F. Trim section in or out of circuit.
4.Trim Gain - provides up to ±8dB of gain at 20kHz.
5.Trim Frequency - sets the +3dB frequency for the shelving 'Trim' filter anywhere
between 2kHz and 20kHz (with Trim gain set for maximum).
6.Hi-Pass Filter Frequency - sets the -3dB frequency anywhere between 10Hz and
150Hz.
7.Graphic Controls - gain of up to ±10dB is provided at each centre frequency. High
quality slider controls feature centre detent for accurate 'flat' position.
8.Peak LED - illuminates as clipping point is approached anywhere within the equaliser
circuitry. Threshold is +20dB.
9.Power LED - indicates unit is powered on.
10.Fixing Holes - for security cover.
GQ600 Page 5

Rear Panel Functions
1.Mains Power - is connected via a standard IEC socket. A compatible power cord is
supplied with the unit.
2.Mains Fuse - is located in a finger-proof fuseholder adjacent to the mains inlet. Always
replace this fuse with the correct type as shown on the rear panel legend.
3.Power Switch - a double pole rocker switch isolates both live and neutral connections.
4.Voltage Selector - switches between two nominal operating voltages. Please ensure
this is set for the correct voltage before operating the unit. Disconnect power to the unit
before resetting this selector.
5.XLR Inputs and Outputs - separate 3 pin XLR connectors are provided for each audio
input and output. All terminations are fully balanced where pin 2 = Hot, pin 3 = Cold
and pin 1 = Screen (shield). See page 8 "Grounding" for more information.
6.Klippon Inputs and Outputs - a six pin Klippon socket is also provided for each
channel. The corresponding plug features screw terminals allowing quick termination of
system wiring, giving the advantages of barrier strip plus the bonus of easier servicing
and the ability to pre-wire. Each connector carries input and output connections with all
terminations fully balanced, where H = Hot, C = Cold, S = Screen (shield).
7.Safety Ground Screw - Do Not Remove.
GQ600 Page 6

Specifications
Inputs Two, electronically balanced.
Impedance > 10k ohms.
CMRR > 65dB 50Hz - 10kHz.
Outputs Two, electronically balanced.
Source Imp. < 60 ohms.
Min. Load 600 ohms.
Max. Level +23dBm into 600 ohm load.
Gain ± 10dB via rotary control.
Frequency Response± 0.5dB 20Hz - 20kHz with controls "flat".
Equivalent Input Noise < -98dBm (20-20kHz unweighted) with controls '"flat".
Distortion @ +18dBm < 0.01% @ 1kHz.
Peak Indicator Threshold: +20dBu.
H.F. Trim
Filter Type 2nd order, optimum phase, shelving.
Frequency 2kHz - 20kHz.
Gain ± 8dB max. @ 20kHz.
H.F. Trim In/Out Front panel switch with LED indicator.
High-pass Filter
Filter Type 12dB/octave H.P.
Frequency 10Hz - 150Hz.
Low-pass Filter
Filter Type 18dB/octave -3dB @ 27kHz.
LPF In/Out Link selectable on PCB.
Equaliser Section
Filters 2 x 30, 1/3 octave, 25Hz- 20kHz.
Filter Type High performance simulated LCR network.
Freq. Tolerance ± 3%.
Range ± 10dB.
Connectors
Inputs 3 pin female XLR.
Outputs 3 pin male XLR.
Input/Output 6 pin Klippon.
Power 3 pin IEC.
Power 110VAC / 220VAC ± 15% @ 50/60Hz.
Consumption < 20W
Weight 5kg. Nett (6.7kg. shipping )
Size 5.25"(3U) x 19" x 9.3" (133 x 482 x 237mm)
excluding connectors.
Options = Optional transformers available.
Perspex security cover.
Klippon BL6 mating plugs.
GQ600 Page 7

Operating Notes
Generally, operating the GQ600 is very straight forward, however certain functions may not
be immediately obvious and these are discussed here.
Low Pass Filter. 18dB/octave filters are provided for each channel to provide additional
H.F. driver protection against unwanted high frequency signals. These have negligible effect
on frequency response at 20kHz. All units are factory set with these filters in, if not required
these filters can be removed from the signal path by changing the position of two jumper
links on the main circuit board, see following diagram.
Output Balancing Transformers. Outputs are fully electronically balanced as standard. If
optional output transformers are required proceed as follows:-
1.Remove four "jumpers" from CN4 and CN8 on main circuit board (located near XLR
outputs).
2.Fasten two output transformers type 7470 to the inside of the rear panel chassis, using
the screws and washers provided, through the two mounting holes located above each
Klippon connector. Plug in transformer connectors into CN4 and CN8.
3.Monitor output noise of unit and rotate appropriate transformer until noise (hum) is at a
minimum. Fasten transformer in this position and repeat for other channel.
Input Balancing Transformers. Inputs are fully electronically balanced as standard. Input
transformers if required, should be requested at time of purchase if possible. if it necessary
to fit input transformers to existing units proceed as follows:-
On main circuit board.
1.Remove R2, R3, R4, R6, R8, R11, R15, R16, R17, R19, R21, R24.
2.Fit R2 and R15 = 10k ohms, R11 and R24 = 0R0 link.
3.Solder in input transformers type LL1540 to positions TX2 and TX3 on main circuit
board.
Grounding. The Screen (shield ) pins on all audio connectors are normally connected
directly to the ground pin of the IEC mains inlet. The chassis is also directly connected to
this pin. Never operate this unit without the mains safety ground connected. Signal ground
(0V) is in turn connected to the chassis ground via a 10R resistor.
GQ600 Page 8

To avoid ground loops, cable shields should be connected to ground at one end only. The
normal convention is that the shield is only connected at the output XLR. Provision is also
made for separately isolating each input and output shield pin permanently within the GQ600
by breaking the appropriate pcb track, where marked with a diamond using a small drill bit or
cutter. See the following diagram for details.
W= Output channel A, X= Input channel A, Y= Input channel B, Z= Output channel B
W
XYZ
Security Cover. A perspex security cover is available to enclose all front panel controls and
so avoid accidental or unauthorised adjustment. To fit this cover proceed as follows:-
1.Fit four M4 x 17mm pillars into the four front panel bushes located in between the six
panel mounting screws.
2.Position security cover over pillars and fasten with screws and washers provided.
Warranty
This product is warranted against defects in components and workmanship only, for a period
of one year from the date of shipment to the end user. During the warranty period, XTA will,
at it's option, either repair or replace products which prove to be defective, provided that
the product is returned, shipping prepaid, to an authorised XTA service facility.
Defects caused by unauthorised modifications, misuse, negligence, act of God or
accident, or any use of this product that is not in accordance with the instructions provided
by XTA, are not covered by this warranty.
This warranty is exclusive and no other warranty is expressed or implied. XTA is not liable
for consequential damages.
GQ600 Page 9