TP-Link RX-7-248 instruction manual Ground loops

*Ground loops

AC ground is provided to the RX-7 and all associated equipment, and this may cause an increase in hum noise if care is not taken in connecting other equipment to the mixer. This is

because a ground loop is made through the shields of the connection cable and the AC line as

shown in Fig. 15, increasing hum noise. To solve this problem, either the chassis ground of the signal line should be disconnected at either piece of equipment, or the chassis earth ground should be disconnected, so that the ground loop is eliminated. This problem can not be easily solved in the case of equipment connected to unbalanced signal lines. However, it is highly dangerous to disconnect the AC ground, as microphone and other equipment connected to the

mixing console are often touched directly by the hand. This may cause an electric shock in the

case of electricity leakage, if any other connected equipment is touched. Therefore the chassis

ground line should be disconnected. Whether to disconnect the chassis ground line of either piece of equipment depends on various conditions, therefore, they should be checked and determined for each installation condition.

In the RX-7, a ground lift switch is provided on the balanced inputs and outputs with XLR type connectors (excluding air monitor inputs and talkback input) to prevent ground loops. This switch is ordinarily set to the NORMAL position, and should be set to the LIFT position

only when ground loops occur.

(Fig. 15)

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