G2 Quick Reference THINGS YOU NEED TO KNOW... ü BOLD MEANS HOLD! Any functions that would produce possible unexpected level changes at the outputs are protected by a `press and hold' action and printed in BOLD on the panel. These functions are: Changing MODE between Gate and Expander; Enabling the sidechain LISTEN function; Ganging the two channels together in STEREO mode. ü The main meters show level, in dB, from the clipping point of the input of the unit just after the analogue to digital converter stage. As the unit is unable to add any gain to the signal, there is no need for an output meter. ü When in Expander mode, the Hold knob has no effect. ü Remember that you won't hear the effect of the parametric sidechain band, unless there is cut or boost applied ­ use the GAIN switch to cycle through the levels. ü The Listen LED always flashes when Listen is enabled. Listen is automatically turned off if the unit is switched off and on. ü Remember that the Range/Ratio control applies to both modes of operation ­ the values in the boxes are for Gate mode, and are in dB, the other values are ratios for Expander mode. Page 2 G2 Operators Manual Contents G2 Quick Reference Important Safety Information Thanks Unpacking the G2 Introduction Features 2 4 5 5 6 6 Front Panel Familiarisation Rear Panel Connections Operating the G2 Switching the unit on and start-up procedure Press-and-hold Keys Minimum and maximum control positions 7 9 10 10 10 10 Noise Gate Know-how Attack and Release Times. Setting the Range Correctly. Using the Hold Time. 11 11 13 13 Expanders and Expansion ­ the subtler approach What does an Expander do? Why are Expanders necessary? How does a Expander work? What is the difference between an Expander and a Noise Gate? 15 15 15 16 18 Sidechain Equalisation ­ How and When to Use it When would Sidechain EQ be useful? How would sidechain EQ normally be implemented? Picking out instruments for gating. 19 19 19 19 Look Ahead Delay ­ Pre-emptive Action Setting the Attack and Release times Gate and Expand MODE STEREO Linking 21 24 25 25 Operating Notes Operating Level Grounding 26 26 26 Specifications Warranty Options and Accessories 27 28 28 G2 Operators Manual Page 3 An example of this equipment has been tested and found to comply with the following European and international Standards for Electromagnetic Compatibility and Electrical Safety: Radiated Emissions (EU): RF Immunity (EU): Electrical Safety (EU): EN55013-1 (1996) EN55103-2 (1996) RF Immunity, ESD, Burst Transient, Surge, Dips &Dwells EN60065 (1993) Important Safety Information Do not remove Covers. No user serviceable parts inside, refer servicing to qualified service personnel. This equipment must be earthed. CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN DO NOT EXPOSE TO RAIN OR MOISTURE ATTENTION RISQUE DE CHOC ELECTRIQUE NE PAS ENLEVER NE PAS EXPOSER A LA PLUIE NI A L'HUMITE It should not be necessary to remove any protective earth or signal cable shield connections. Do not defeat the purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding type plug has two blades and a third grounding prong. The wider blade and the third prong are provided for your safety. When the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. Only use this equipment with an appropriate mains cord. In the USA the cord should comply with the requirements contained in the Standard for Cord Sets and Power Supply Cords, UL 817, be marked VW-1, and have an ampacity rating not less than the marked rating of the apparatus. Page 4 G2 Operators Manual Thanks Thank you for choosing the XTA G2 Dual Gate/Expander for your application. Please spend a little time reading through this manual, so that you obtain the best possible performance from the unit. All XTA products are carefully designed and engineered for cutting-edge performance and world-class reliability. If you would like further information about this or any other XTA product, please contact us. We look forward to hearing from you in the near future. Unpacking the G2 After unpacking the unit, please check it carefully for any damage. If any is found, immediately notify the carrier concerned - you, the consignee, must instigate any claim. Please retain all packaging in case of future re-shipment. G2 Operators Manual Page 5 Introduction The G2 is a powerful DSP based audio dynamics processor, ideally suited for live sound applications, where it combines the accessibility and immediacy of a pure analogue design with the quality and accuracy of a digital design in a compact 1U unit. To achieve this, the G2 has an analogue control surface, following the `one control ­ one function' philosophy and a pure digital signal path, with 24-bit conversion, 40-bit internal processing and a professional 48kHz sampling rate. The G2 is also available with optional AES/EBU digital inputs and outputs. Features Look ahead attack for true `clickless' operation and instantaneous opening of the gate Fully adjustable envelope controls, including hold time (in Gate mode) with large, easy to see, metering Sidechain EQ built-in including low and high pass filters, and an additional parametric section with variable stepped gain and high-resolution frequency adjustment Expander mode ­ for more subtle gating applications, with gain reduction metering and fully variable ratio control Stereo link mode locks the sidechains together for perfect stereo tracking as well as parameter matching Threshold metering to allow accurate and repeatable triggering of the gate AES/EBU Digital input and output interfaces are available as an option. Input and output balancing transformers are also available as an option. Page 6 G2 Operators Manual Front Panel Familiarisation Level Meter: this meter displays the instantaneous available headroom available at the input, just after the analogue to digital converter. Active Key: Switches the entire channel on/off ­ LED illuminated when processing is active. Note that the Listen mode may still be active when the channel is bypassed. Threshold Control: Set the threshold at which the gate will open, from -40dBu to +22dBu (effectively off). Threshold Meter: This meter display the closeness to the threshold, ranging itself dependant on the setting of the Threshold control and the input level. The yellow LED shows the point at which the gate will open. Attack Control: Set how fast the gate will open (the fade-in time) ­ the `60uS' setting uses look ahead delay to open the gate before the main signal arrives, so preserving the entire waveform. Hold Control: Set how long the gate stays fully open after the signal has dropped below the threshold, and before entering the release phase. Release Control: Once the signal has dropped below the threshold and the hold time has expired, this control determines how quickly it is attenuated (the fade-out time). Gate and Gain Reduction Metering: The large green LED is only ever illuminated when there is less than 6dB of attenuation on the channel (so effectively the gate is fully `open'). As the attenuation increases, this LED goes off, and the red meter begins to illuminate right to left. This shows increasing gain reduction, until the final large red LED illuminates when there is more than 40dB of attenuation. Range/Ratio Control: In Gate mode, this control sets the maximum attenuation allowed (the Range) when the gate is fully closed. Note that if the Range is set to less 40dB, the large RED led may never illuminate. In Expand mode, this control determines the degree of attenuation as the signal drops below the threshold. MODE Key: Switch the channel between Gate mode and Expand mode. HOLD this key to change modes. Note that the control markings for Gate mode range are boxed. G2 Operators Manual Page 7 Sidechain PEQ Gain Key: Adjust the gain of the sidechain filter to sensitise or desensitise the gate to certain frequencies. +8/12/20(!) of gain is available, as well as 0db (off). Sidechain PEQ Type: Choose the shape of the sidechain filter between, narrow `Q' parametric and `wide `Q' parametric. Sidechain PEQ Frequency: Select the frequency range over which the sidechain filter will operate. High Pass Frequency Control: Cut low frequency content out of the sidechain signal up to 5kHz. Low Pass Frequency Control: Cut high frequency content out of the sidechain signal down to 250Hz. LISTEN Key: Switches the output of the sidechain filter into the main signal path, so that the required range of frequencies may be more easily selected. LED flashes as a reminder that this is selected. HOLD to engage this function. STEREO Key: Enabling the `Stereo' mode will disable the right hand set of controls and force both channels to assume the parameter values of the left channel. The sidechains are also linked so that the two channels track perfectly, maintaining the stereo image. Page 8 G2 Operators Manual Rear Panel Connections Power Switch: turns the units mains supply off and on. Mains Fuse: located in a finger-proof holder adjacent to the mains inlet. A spare fuse is also located in this holder. Mains Inlet: connected via a standard IEC socket. Audio In-Out: 3 pin XLR sockets are provided for each channel. All are fully balanced, pin 2 hot, 3 cold, 1 screen. Always replace the fuse with the correct type and rating as shown on the rear panel legend. G2 Operators Manual Page 9 Operating the G2 Operation of the G2 is very straightforward, but there are a few points worth noting which, once understood, will make using the unit even easier. Switching the unit on and start-up procedure After plugging in the power and switching the power on using the rear panel switch, confirmation is quickly given that all is well by various status LEDs illuminating almost immediately after power-up. These will include, as a minimum, MODE (Gate/Expand); and Sidechain EQ Type (Wide/Narrow `Q'). The gain reduction will animate and, after the bypass relays disengage, begin to `count down' accompanied by the output level fading up to normal operating level. The entire process is complete when the input/output meters and gain reduction begin to operate normally. This whole start-up procedure only takes a few seconds. Press-and-hold Keys The legending on the front panel alerts the user to the fact that several keys require a `press and hold' action to initiate them. These keys relate to functions that could accidentally introduce large changes of level at the outputs, causing undesirable effects and possible damage. These keys have their function marked in BOLD (and a different font) to make it clear that they will only change state if the key is held in for a time. The keys in question are... MODE ­ switching between gate mode and expand mode (See page 25) LISTEN ­ switching the output to monitor the sidechain EQ signal (See page 19) STEREO ­ linking the two channels together to operate in stereo (See page 25) Minimum and maximum control positions To ensure that the G2 is 100% accurate all of the time, and that what it says on the front panel is exactly what the unit is doing, it has been necessary to introduce `end-stops' on the controls. The extreme regions on each control marked with the curved line designate this entire region as relating to the parameter value shown. This is to compensate for the mechanical tolerances of the potentiometers. Page 10 G2 Operators Manual Noise Gate Know-how Most engineers know the principle reason for using a noise gate ­ to shut off the output of some device that, in the absence of the desired output signal, produces (or passes on) an undesirable level of background noise. The behaviour of the noise gate is controlled by adjusting, principally, its threshold. This sets the point at which the level of the desirable signal is deemed quiet enough to turn it off, thereby cutting off all the background noise as well. Considering the diagram shown here, the desired signal would be the high level burst and, in between, low level noise. An example of this scenario might be the signal from a bass drum microphone ­ a burst of signal, but perhaps with unwanted pickup from lighting dimmers producing a background buzz. Setting the threshold just above the level of the buzz would keep the gate closed during periods were the bass drum was not being played, only allowing signal through when the output would be sufficient to mask the noise anyway. The output graph above highlights several other points that are particularly important with noise gates. Attack and Release Times. As the gate opens, there will be a finite delay before the signal crosses the threshold, cutting off part of the start of the desired signal's envelope. Similarly, as the signal drops below the threshold, the gate will close, cutting off some of the end of the envelope. The diagram ...