User manual XTA C2

[. . . ] C2 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: Switching AUTOmatic time constants on and off; Changing MODE between compressor and De-EQ; Enabling the sidechain LISTEN function; Ganging the two channels together in STEREO mode. ü The meters show level, in dB, from the clipping point of the unit ­ when the METER switch is set to `IN' the meters show level, in dB, from clipping the input converter. [. . . ] To hear this control signal, it is necessary to monitor the sidechain path. The sidechain LISTEN signal may be monitored at the output, using the LISTEN key on the front panel. If the signal has been heavily compressed, chances are the overall level will have dropped considerably. At this point it might be necessary to introduce some additional gain to compensate for this loss. Make-up Gain Section: The introduction of extra (static) gain is best applied by ear, but the use of the metering will aid the process. The intention is to make the input and output levels of the unit match. Frequent comparisons using the `ACTIVE' key to bypass the unit, and watching the gain reduction meter, which will show the instantaneous amount of compression being applied, are the keys to matching the levels. Limiter Module: Separate to the compressor is a fully independent limiter module. It determines the absolute maximum output level from the unit, set with the threshold control. However, the LISTEN signal does not get routed through the limiter, so be careful when engaging the sidechain monitoring. Output Section: As mentioned in the limiter section, the LISTEN key is located just before the output stage, and routes the output of the sidechain (equalised or not) to the main output, so that it can be accurately tailored to achieve the desired response. The output is then converted back to analogue or transmitted as a digital signal to an independent output. Note that the digital output is a factory fitted option ­ please see Appendix 1 for further information about this. Now that the main building blocks have been explained, their interactivity and connections can be outlined with reference to the two modes of operation. C2 Operators Manual Page 15 Compressor MODE Below is the block diagram showing how the compressor works. Following the input section, the signal is split into the main path (audio) and the sidechain (control). The main path consists of the gain control element, followed by the make-up gain section, then through the limiter and directly to the output. The sidechain may be equalised by passing it though the EQ section, and this equalised signal may be monitored by engaging the LISTEN function. In this mode, the sidechain control signal may be equalised to make it more or less sensitive to certain frequencies. This will in turn affect the threshold of the compressor, making it compress to a greater or lesser degree depending on the frequency content of the incoming signal. However, no matter how the sidechain is equalised, the compression is applied to the entire main signal ­ and all frequencies are reduced in gain by the same amount. The introduction and use of the sidechain EQ adds the facility to make this `frequency conscious'. Page 16 C2 Operators Manual DE-Eq MODE Below is the block diagram showing how the De-EQ mode works. Following the input section, the signal is split into two paths, which are eventually recombined to form the main signal path again. One signal passes through the equalisation sections that, in this mode, operate slightly differently to the sidechain EQ for the compressor mode. [. . . ] Additionally, the sidechains will be linked so that, if one channel compresses more than the other, the same amount of compression will be applied to both channels, 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. This might have a dramatic effect on the level of the channel, so be careful! Page 26 C2 Operators Manual Operating Notes Operating Level With any audio signal processing equipment it is necessary to ensure adequate signal level is used through the device, to avoid sacrificing noise performance. It is suggested that the operating level chosen should give adequate level to just light the -12dB LED on the headroom meter with maximum program level being used. [. . . ]