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General Information on using the mixing console
*
Impedance
Generally speaking, there are two rules to follow when connecting equipment outputs to the
inputs of other equipment.
1. Try to properly match the impedances of the outputs and inputs.
2. Connect low impedance outputs to high impedance input.
The above rules about impedance are very important and should be taken into consideration
in all connections between equipment.
* Difference between Professional and HI-FI type equipment
Microphones, tape recorders, wireless tuners, and various other equipment may be connected
to the inputs of the mixing console. The associated equipment to be connected to the mixer
outputs includes graphic equalizers, limiters, compressors and power amplifiers. The RX-7 is
equipped with an accessory send (output) and receive (input) on each input module (IPM-7)
and group module (GFM/GEM-7). Various equipment such as echo and reverb equipment,
graphic equalizers, and noise gates, are available as associated equipment to be connected to
the accessory send and receive. All the above associated equipment are generally grouped for
professional use and HI-FI use (for consumer use) regardless of their functions. Generally, the
output of professional equipment is balanced (transformer-isolated) with an impedance of 600
ohms and is designed to drive 600-ohm or higher impedance loads. The nominal output level of
most professional equipment is +4dB (1.23V RMS). As for the input/output terminals, XLR
type audio connector or TRS type connectors are employed for professional equipment.
The output of HI-FI equipment is generally unbalanced with an impedance of several kilo-
ohms and designed to drive lOK-ohm or higher impedance loads. The nominal output level of
most HI-FI equipment is —20dB to —l0dB. RCA pin connectors are employed for the
input/output terminals of HI-FI equipment.
* Balanced type and unbalanced type
If there is any problem as to the grounding method or if cable has to be extended (over 10 feet),
experience proves that hum or noise is picked up easily unless the balanced type is used. In the
RX-7, balanced (transformer-isolated) circuits are employed for input/output terminals
necessary for long cable connections, but unbalanced circuits are employed for input/output
terminals to be connected to adjacent associated equipment.
Recently, electronically balanced circuits have been used in some professional equipment
instead of transformer-isolated balanced circuits. It must be noted that special care should be
taken as to the grounding method and ground line connection when using equipment with
electronically balanced circuits. In particular, problems may occur if an electronically
balanced output is connected to the unbalanced input of other equipment. This will not occur
with transformers because the transformer-isolated, balanced circuit is not only balanced, but
isolates other equipment, thus reducing the possible problems. The electronically balanced
circuit, on the other hand, has advantages of better frequency response and quicker slew rate.
However, when applying it for on-the-road use where each set-up differs, trouble may occur
more often as compared with the transformer-isolated circuit.
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