Shure 404B, 404C User Guide

Model 4048 is a low-impedance microphone with a four-conductor (two conductors shielded) coil-cord cable and a single-throw double-pole leaf-type switch to control the microphone circuit and an external relay or switching circuit. The GREEN and WHlTE leads are the "hot" conductors for balanced-line connection to the microphone circuit; the shield is connected to the microphone circuit ground. The RED and BLACK leads control the relay or switching circuit. The microphone circuit of the switch is normally open but can be easily modified for normally shorted operation.

The Model 4048 is wired for balanced-line operation and is recommended for use where long cable lengths are required or conditions where severe hum pickup may exist. The Model 4048 can be connected directly to the input of a low-impedance amplifier or a Shure A95 Series Line Matching Transformer can be used for coupling the Model 4048 to the input of a high-imped- ance amplifier. A two-conductor shielded cable can be used for extending only the microphone circuit. If both the microphone and remote circuits are to be extended, a four-conductor cable should be used with two shielded conductors for the microphone circuit.

Model 404C is a high-impedance microphone with a three-conductor coil-cord cable (one conductor shielded) and a single-throw double-pole leaf-type switch to control the microphone circuit and an external relay or switching circuit. The WHlTE lead is the "hot" conductor for connection to the microphone circuit; the shield is connected to the microphone circuit ground. The hangup button and the wire strain relief are also grounded to the cable shield in the 404C only. The RED and BLACK leads control the relay or switching circuit. The microphone circuit of the switch is normally shorted but can be easily modified for normally open operation.

Model 404C can be used with any amplifier having a high-impedance microphone input. A single-conductor shielded cable can be used for extending only the microphone circuit. If both the microphone and remote circuits are to be extended, a three-conductor cable should be used with one shielded conductor for the microphone circuit. Cable lengths over 15m (50 ft) are not recommended.

Model 4048 Circuit Modification: The microphone circuit of the 4048 is open when the microphone switch button is in the normal position. The microphone can be modified to provide a normally shorted microphone circuit as follows:

1.Remove the three No. 5-20 pan head screws from the back of the microphone case. (Caution: the

SWITCH	MU-METAL
BUTTON,	SHIELD7

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FIGURE 3

the microphone cartridge is spring loaded and care must be taken to hold the two halves of the microphone case firmly together.)

2.Separate the case front and back and remove the switch button. See Figure 3.

3.Remove the No. 5-40 round head switch mounting screw and lock washer holding the switch assembly in the case back.

4.Disconnect or clip the WHlTE cable lead from the switch solder lug.

5.Strip the insulation from the WHITE lead approximately 6 mm (Y4 in.) and solder the WHlTE lead to the switch blade next to the blade with ttle GREEN lead connections. (This is the blade that the switch button pushes against.) The outside solder lug may be bent out of the way to aid soldering.

6.Reassemble the switch in the case back using the previously removed screw and lock washer.

7.Replace the switch button in the case back.

8.Making certain that the cartridge shield retaining springs are in the proper position and that no leads are pinched, place the case back on the case front and firmly press the cases together.. Fasten with the three previously removed No. 5-20 screws.

Model 404C Circuit Modification: The microphone circuit of the 404C is shorted when the microphone switch button is in the normal position. The microphone can be modified to provide a normally open microphone circuit as follows:

1.Remove the three No. 5-20 pan head screws from the back of the microphone case. (Caution: the microphone cartridge is spring loaded and care must be taken to hold the two halves of the microphone case firmly together.)

2.Separate the case front and back and remove the switch button. See Figure 3.

3.Remove the No. 5-40 round head switch mounting screw and lock washer holding the switch assembly in the case back.

4.Disconnect or clip the WHlTE cable lead from the switch solder lug.

5.Strip the insulation from the WHlTE lead approximately 6 mm (Y4 in.) and solder the WHlTE lead to the unused solder lug at the bottom end of the switch.

NOTE: In certain instances where switch sequence is critical, it may be necessary to remove the effect of the shorted switch on the cartridge. This is done by insulating the shorting contacts with a piece of "spaghetti" tubing or a piece of insulating tape.

6.Reassemble the switch in the case back using the previously removed screw and lock washer.

7.Replace the switch button in the case back.

8.Making certain that the cartridge shield retaining springs are in the proper position and that no leads are pinched, place €he case back on the case front and firmly press the cases together. Fasten with the three previously removed No. 5-20 screws.