OPERATING CONSIDERATIONS (Cont’d)
conference or conversation situation, with several micro- phones “live” but only one speaker talking at a time, each Input control should be set so that each speaker results in approximately the same amount of compression, observing that the overall level is correct for proper Gated Memory action.
SIMULTANEOUS MIXED INPUTS
W ith simultaneous (mixed) inputs, the compressor will automatically maintain a constant overall output level, so that the balance among the sources may be adjusted easily by monitoring with headphones. Simply observe that the DB Compression meter (7) is reading in the normal oper- ating range and that Gated Memory action is proper.
AUTOMATIC “DUCKING”
The balance between two sources may be adjusted to produce automatic “ducking,” for example, for an an- nouncer’s voice over musical programming. In this case, set the Input control for the music source for a low amount of compression, such as 5 dB. Then set the announcer’s microphone Input control for 15 dB compression when he is speaking. When the announcer talks during music, the SE30’s gain will be reduced by 10 dB, “ducking” the music level below the voice level by that amount. When he stops speaking, the music will return to full output.
ADDITIONAL INPUTS
To accommodate more inputs than three, a Mix Bus jack (12) is provided which may be connected to a similar jack on another SE30 or M67 Mixer. When a Mixer with a mix bus is used in conjunction with the SE30, a compressed output may be obtained from the SE30, and an uncompressed output of the same mixed material will be available from the Mixer.
Inputs may also be added by connecting the line level or microphone level output of another mixer to one of the SE30 inputs.
EXCESSIVE AMBIENT NOISE
Under | certain conditions, such | as | high noise | levels, |
it may be | impossible to adjust the | Input | control (1) | so that |
the Gated Memory can consistently discriminate between background and program. In such a case, the Gated Mem- ory switch (21) should be set to Disable and the amount of compression should be reduced to minimize the audible effects of “pumping.”
In extremely severe cases, compression should not be used at all, since the increase in background noise during pauses will be quite unpleasant. The SE30 may then be used as a
FADING TECHNIQUE WITH COMPRESSION
Fading of inputs with a compressor must be accom- plished somewhat differently than with a linear mixer. Since a slow reduction of input level within the compres- sion region will be compensated for by an increase in gain, no audible fading will occur. Consequently, fading an input down should be done rapidly, at least to the point at which the Gated Memory changes to the “hold” state.
For overall program fades, it is desirable to use the Output control (3), since it does not affect the amount of compression but only the output level.
SPECIAL APPLICATION
CONSIDERATIONS
SOUND REINFORCEMENT
The SE30 may be used in sound reinforcement installa- tions, but some care must be exercised in such applica- tions. Since this compressor can only reduce its gain when a signal exceeds its compression threshold, maximum gain occurs with low signal levels, and the
STEREO OPERATION
Two SE30’s may be synchronized to operate together for stereo applications by interconnecting their Stereo Parallel jacks (23) and performing the adjustment procedure out- lined in the Service Section of the manual.
One unit will compress the left channel signal and the other will compress the right channel signal, but both will respond equally to the sum (left and right) signal to mini- mize apparent stereo image shift.
Because of the necessity of providing the two units with a properly balanced stereo signal, it is recommended that stereo applications be restricted to single inputs for each channel, with mixing and balancing being accom- plished in another mixer prior to the SE30’s.
SINGLE INPUT PROGRAM COMPRESSOR
When the SE30 is used as a single line input, perma- nently installed program compressor, it is possible to im- prove the
RESPONSE RATE KNOB REMOVAL
To prevent inadvertent misadjustment of the Response Rate control (6) the knob may be removed and the hole filled with the plastic plug included with the SE30. This procedure is described in the Service Section.
THEORY OF OPERATION
(See Figure 3)
Operation of the SE30 Gated Compressor/Mixer may be explained by referring to the Functional Block Diagram, Figure 3. The active devices in each stage, as well as other important components, are identified by their reference numbers, for ease of location on the Schematic Diagram (Figure 4) and the Chassis Parts and Printed Circuit Board Parts Placement diagrams (Figures 5 and 6). The first digit of
INPUT-OUTPUT SIGNAL PATH
Balanced input signals entering through J1, J2, and J3 are amplified by the three
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