User manual XTA G2

[. . . ] 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. [. . . ] This distinction is important because if the expander was to process the dynamic range at a certain threshold, attenuating below the threshold and amplifying above, even with a low ratio of perhaps 3:1, a limited dynamic range signal might well end up with a dynamic range well in excess of 120dB, which would be impossible to utilise, even with the best equipment. The main use for an expander is to improve the dynamic range of an instrument or processing device. The dynamic range of any device is limited by two factors ­ it's minimum output, and it's maximum. It would seem reasonable to assume that the minimum output would be exactly zero, and that this level should be the same for all devices. Certainly, when the majority of instruments and devices are turned off (assuming they are powered in some way) they will all share a similar minimum output level. However, once on, it is the noise floor of the electronics within that determines the minimum output. A signal that is below the noise floor of any piece of equipment will not be resolved by that equipment. The maximum output level is largely determined by the power supply capabilities of the device. Many manufacturers (especially Far Eastern) tend to use power supplies with lower voltage rails, resulting in a poor drive capabilities and limited maximum output level. As the expander functions below the threshold, it is in the area of minimum output level that improvements can be made. Thinking laterally, the noise floor need not just refer to the electronically generated variety. Noise can be thought of as any "irregular fluctuations accompanying a transmitted signal but not relevant to it"1. This may now include other sources of noise such as: Hum due to poor power supply regulation or induced by an earth loop Background interference from lighting dimmers Stage noise picked up from a microphone or transmitted up a microphone stand Handling noise from a microphone Overspill when `miking-up' a drum kit 1 Concise Oxford English Dictionary 2000 Definition 3. G2 Operators Manual Page 15 An expander can be used to improve the noise floor under all these circumstances, by attenuating signals below a set threshold, thereby improving the clarity of the signal fed to it. One other area where expander can prove useful is in the control of feedback in a live situation. In the case of a vocal microphone, leaving it `open' all the time is likely to cause problems not only with the pick-up of extraneous noise, but allowing feedback paths to build up. Whilst the vocalist is actually using the microphone, their voice effectively stops all other sounds from entering. By attenuating the output from the microphone during pauses, the build up of feedback can be avoided. Regions 1 and 3 are set to below the threshold of the expander, and will consequently be attenuated by an amount equating to the Ratio parameter. In region 2, the signal has risen to a level above the threshold, and so the expander will stop attenuating, and allow the signal to pass straight through. The difference between the attenuated signal when below the threshold and the original signal level (i. e. Continuing with the compressor analogy again ­ the ratio can be determined by considering the degree of attenuation required. If the signal drops to 6dB below the threshold, and the ratio is set to 2:1, then the actual output will be 12dB down. The expander is equipped with a set of envelope controls, which allow adjustment of how it reacts to the signal as it crosses the threshold. Page 16 G2 Operators Manual Examining the purple shaded area in region 3, this represents the release time of the expander- that is the time for it to achieve full attenuation by the amount set with the Ratio control, once the signal has dropped below the threshold. [. . . ] STEREO Linking Pressing and HOLDING the STEREO key will illuminate the LED and gang the two channels of the unit together. This has the effect of disabling the controls for channel B, as both channels will assume the settings on channel A. Additionally, the sidechains will be linked so that, if one channel opens so will the other, so avoiding any shifts in the stereo image. Note that as soon as the stereo linking is turned off, channel B will assume the parameters as set by its controls. [. . . ]