Midas Consoles U16, U32, U24 Effect of EQ, Dynamic processing, Appendix C Application Notes

88 Appendix C: Application Notes

channels will receive the same signal at the same time so, typically, when 16 channels are summed together a gain of around 5dB to 8dB will be seen. It is important to leave some headroom in the summing amplifiers so that they do not overload, should the sum exceed the maximum level.

The effect of EQ

Channel equalisation should be used with care. Boosting or cutting equaliser bands can make monitoring your actual input level very difficult. Excessive boosting of EQ (+15dB is available on each band) will have the same effect as applying more gain to the input, taking up valuable headroom. Consider backing off the channel gain when using large amounts of boost (if you have to use large amounts of boost) to retain a sensible level at the output.

Excessive EQ cut can have a similarly undesirable effect. If a large amount of signal is cut in the equaliser section, gain may be used to ‘make up’ the level lost in the equaliser. However, the input pre-amplifier still has the same amount of available headroom. If gain, added to ‘make up’ the loss in the equaliser, exceeds the maximum level into the microphone pre-amp then the channel won’t appear to be overloaded, but the microphone pre-amp will. Turning off the equaliser will reveal the true story, whereby the microphone pre-amp may be overloaded. It is worth considering whether such large amounts of EQ cut is really required, or whether it is being used rather more as a volume control (in which case the input gain could be set to a normal operating level and the output adjusted on the channel fader).

You can monitor the level pre-EQ and post-EQ using the LED meter by switching the EQ in and out during sound check.

Dynamic processing

When working with signals that are constantly at a high level the channel gain can accommodate these signals with ease. When working with varying signals, such as from a vocalist, it may be desirable to reduce the dynamic range of the signal so that the loud parts aren’t so loud (and don’t overload your channel input) and the quiet bits aren’t too quiet (so the signal to noise ratio would be increased).

Limiters and compressors have a similar function, which is to reduce the dynamic range of a signal. The means by which they do this won’t be discussed here, but these devices have the ability to reduce the level of loud signals automatically and also raise the gain to ‘make up’ the level as desired. The channel gain can now be set with adequate headroom to accommodate both loud and quiet signals, and the compressor can reduce the dynamic range and ‘make up’ any reduction in level. By inserting such a device into the channel’s insert point you have the ability to remove the guesswork from setting your system gain.

However, there are still sources of potential problems. The VeniceU is able to operate at levels up to +21dBu on both the insert send and return. If the maximum input level of the compressor was less than +21dBu, it is possible to overload the input of the compressor. The only way to resolve this situation would be to drop the channel input gain so that the input level of the compressor was not being overloaded. However, please note that the level returned from the compressor would also be lower than +21dBu and excessive use of the compressor ‘make up’ gain would overload the output of the compressor!

VeniceU Operator Manual