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. [. . . ] Sidechain EQ Sections: The signal used for controlling the main path may be equalised prior to its use as a control signal ­ this enables it to be made more or less sensitive to certain frequencies, changing the way the compressor reacts the audio. The degree of sensitivity may also be also be adjusted (the Sidechain EQ Gain control) when in compressor mode. More on this later. This signal (suitably equalised) is then passed into the control section where it is used to determine the degree of compression of the main signal and how this is applied. Control Sections: This control signal is compared against the threshold setting to see if it is to start affecting the main path. Included in this section is the ratio control which determines how severely the main signal is compressed as it continues over the threshold, and the attack and release times which determine how quickly the compressor reacts and `leaves go' as the threshold is crossed. This signal is now used to directly affect the gain (in compressor mode) of the main signal, and conceptually does so using the . . . Page 14 C2 Operators Manual Gain Control Section: This element is simple in its operation ­ the signal to be controlled passes straight through, and the signal fed in from the side can `turn down' the main signal, but is never heard itself. 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. This follows the compressor and is post-make-up gain at all times. 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. [. . . ] It should be noted that the figure quoted for the maximum input level options is the clipping point for that option (not a safe operating level). Always ensure that this clipping point is no lower than that for the following equipment in the signal chain, and allow extra margin if equalisation sections are boosted. 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. [. . . ]