VocoPro CLG-600 owner manual Compression for Feedback Control Procedure

Typical Applications (cont.)

Compression for Feedback Control Procedure:

1.Set up the CLG-600 unit's controls as follows:

a.Output level control to -20dB.

b.Input Gain control to 0dB.

c.Threshold control to -30dB.

d.Ratio control to infinity ()

e.Attack time to 5mS.

f. Release time to 1 sec.

2.Adjust equalizer controls to a flat setting, and if the equalizer has an overall volume control, boost it by 10 to 15 dB.

3.Open up several microphone input channels to a normal operating level, with typical EQ settings, and turn the console master fader up to a louder than normal setting. At this point, the system should be well into feedback, but the room volume will be constant due to the action of the limiter. You can listen to the feedback at any level you like by simply varying the CLG-600's output level control, although below a certain monitoring level, the feedback will stop.

4.Try to determine the feedback frequency, and then equalize it by adjusting the center frequency, bandwidth, and boost/cut controls of your parametric equalizer. (Note: a graphic equalizer can also be used, although with less accuracy.) After eliminating the problem frequency, try to further define it by sharpening up the bandwidth, re- attacking the frequency control, and making the cut shallower, if possible.

5.As soon as the first feedback frequency has been removed, bring up system gain until another feedback point is induced. Repeat the equalization procedure until it becomes impossible to distinguish individual, predominant feedback frequencies.

6.Return all mixer, EQ overall gain, and compressor/limiter gain controls to normal settings.

Recording

The limiter can be used to prevent tape saturation in analog recording. Also, with modern trends toward inexpensive digital recording, it remains necessary to protect against input overload. With digital recording, the information stored on tape, hard disk, optical disk, etc., is either a 1 or 0, so actual signal level on the tape is not the concern it is with analog recordings, in fact it is not even a user controllable parameter. What is of concern however, is the signal level applied to the A-D (analog to digital) converters. If clipping occurs at the converter input stage, the resulting distortion is most unpleasant, and will be recorded digitally as if they were part of the original audio signal, forever mixed with the audio. To prevent converter distortion while preserving the extended dynamic range of digital recording, look up the max input level of your recorder/converter and set up the limiter as follows:

1.Set Gain to 0.

2.Set Threshold to 2-3 dB below max converter input.

3.Set Ratio to 10.

4.Set Attack to 2 mS.

5.Set Release to .2 Sec.

6.Set Output level to 0.

If you are exceeding threshold frequently, your input signal is probably too high and should be turned down. Of course, every situation is different, so experimentation before final recording is always a good idea, but this is a good starting point. To obtain a gentler limiting action at the expense of some dynamic range, decrease the threshold to -15 and the ratio to 3-5. This is also a good starting point for analog recording.

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