￿$￿O￿O￿H￿J￿U￿R￿6￿R

the output level of both left and right channels. Note that the headphones output level is high enough for use as an auxiliary unbalanced line feed to drive a tape deck or a power amplifier.

Input 1–4 XLR Connectors: are balanced, professional, three-pin audio connectors. Pins 2 and 3 are “hot,” and pin 1 is ground. For microphone operation, the Input Mic/Line switches must be in the Mic position; for line level inputs, the switches must be in the Line position. Phantom Off/On Slide Switch: controls the application of phantom power for condenser microphones to all inputs. With the switch on and Input Mic/Line switches in the Mic position, +30 Vdc is applied to pins 2 and 3 of each input connector. Series current- limiting resistance is 3.3 kilohms for each input. When using other than Shure condenser microphones, verify that the voltage and resistance requirements are compatible.

Output L and R XLR Connectors: are professional, three-pin audio connectors for connection to either low-impedance microphone or line-level inputs of power amplifiers, mixers, or other signal-processing equipment. The Output Mic/Line switch selects either microphone - or line-level output signals.

Mix Bus L and R Phono Pin Jacks: provide direct access to the left and right output channel mixing buses. This facilitates stacking or “multing” FP42s to achieve additional input capacity without losing any inputs. With two FP42s connected at their mix bus jacks, for example, the left and right mix buses of each unit are directly con- nected, providing two independent (ganged) master gain controls and two isolated line amplifiers with eight individually controlled in- puts. Since the buses are directly connected, a 6 db drop in the gain of each output channel will occur, and the master or input controls must be increased to compensate.

INSTALLATION AND OPERATION

Battery Operation

In addition to 120- or 240-volt ac operation, the FP42 can be operated from an internal battery pack. Current drain is typically 32 mA at + 4 dBm output level. Battery operation is recommended for re- mote, on-location operation, and as an emergency backup source in case of ac power failure.

Access to the battery compartment is through the bottom of the chassis. Three 9-volt transistor radio batteries power the FP42 at full rated output. Use alkaline batteries for maximum life. Battery life is approximately 10 hours at +4 dBm continuous use. Note that phantom power loading will increase battery drain.

With batteries in the battery compartment, the FP42 will automatically and silently switch to battery operation should the ac voltage fall below a suitable level.

Battery condition can be determined by using the Batt Check switch on the front panel. With the FP42 power switch on, activate the Batt Check switch, and observe the VU meter. A new set of batteries will give about a +2 VU indication. Battery condition is good if the reading is above 0 VU; a lower reading means that new batteries are required for proper operation. (Note that the FP42 power switch must be turned on to check battery condition.)

Connections

Connect the signal sources to the three-socket XLR Input connectors and set the Mic/Line switches for the proper level. Connect the three-pin XLR Output L and R connectors to low-impedance microphone or line-level inputs of power amplifiers, mixers, VTRs, etc. Set the Output Mic/Line switch for the appropriate signal level.

If desired, connect additional FP42s or other mixers using the Mix Bus phono pin jacks. A common ground connection can be established using the rear-panel Ground binding post.

Connect the line cord to a 120 Vac +10%, 50/60 Hz source if the FP42 is to be ac-operated. If 240-volt ac operation is desired, refer to the Service section.

2

Adjustments

Turn the Power switch to the On position (VU meters will light in ac operation). Turn the Phantom switch on if non-battery-operated condenser microphones are to be used with the FP42. (Caution: Do not turn the Phantom switch on when using unbalanced low-impedance microphones; objectionable hum will result.) Note that phantom power cannot be applied to the inputs with the Mic/Line switches in the Line position; if line-level condenser microphones (such as Shure’s SM82) are to be operated on phantom power, contact Shure’s Customer Services Department for modification in- structions.

Turn the Limiter switch to Out. For each input channel, apply an input signal and rotate the associated Pan control to assign the signal to the left or right output channel as desired. Adjust the Channel Level control for each channel so that the VU meter needles move with the audio signals in the 0 VU to –20 VU range, with occasional movement into the 0 VU to +3 VU (red) area. With the limiter out, the red Peak/Limiter LEDs will flicker as the signal level approaches clipping.

If desired, activate the Lo Cut Filter switches above the Channel Level controls. The filter action will help reduce wind noise and undesirable low-frequency signals such as from condenser microphones or turntable rumble (see Figure 1).

LO-CUT FILTER ACTION

FIGURE 1

Note that each input Channel Level control has a cuing capability. To cue a channel while the other channels are carrying program material, pull the desired channel Level control outward to the cue position. This removes that channel from the mixing circuitry and routes it only to the Headphones jacks. Adjust the Headphones level control to a comfortable listening level, and adjust the cued channel Level control for a proper mixing level. Restore the cued signal to the program mix by pushing the Channel Level control inward.

The limiter circuit is activated by the Limiter switch. With the switch set to In, mixer output is limited to the preset threshold level of +14 dBm. Increasing the Channel Level or Master gain controls increases the average output and the amount of limiting. To adjust the limiter threshold, refer to the Service section.

With the limiter circuit in, the Peak/Limiter LEDs light to show limiter action. The LEDs respond much faster than VU meters and are activated by extremely short transient peaks, but remain on long enough for easy recognition.

VU Meter

The VU meters are factory-calibrated for use with a 600-ohm terminated line. The VU Range switch on the rear panel selects either a +4 or +8 dBm output at 0 VU meter indication. (This switch changes the meter indication but does not change the actual output level.) Microphone output levels are 50 dB below line output. The +4 range

￿$￿O￿O￿H￿J￿U￿R￿6￿R￿X￿