Shure FP24 Output Panel Connectors, Operational Notes, Side Output Panel, Input Transformers

Output Panel Connectors

2	3
1			4
TAPE RTN
1(L)		2(R)	5
			5±14 VDC
	LINE OUTPUTS		± +

Figure 3. Side Output Panel

1.Strap Slot

Attachment point for camera straps.

2.Tape Return Input Connector

3.5 mm (1/8 in.) TRS stereo (unbalanced) input for head- phone monitoring of external audio sources.

Tip = left, ring = right, sleeve = ground.

3.Left and Right Line Level Outputs

Active-balanced XLR line-level outputs. +22 dBu peak out- put level. Pin 2 = hot, pin 3 = cold, pin 1 = ground. Pin 3 can be grounded or ungrounded to drive unbalanced inputs.

4.Battery Compartment

Houses two AA batteries. Insert positive (+) end of batteries first.

5.External DC Power Input

Accepts 5±14 VDC from an AC to DC transformer or a bat- tery supply. Locking, threaded coaxial connector.

Center pin = positive, sleeve = negative. Use the supplied threaded connector for power supplies with plug-type con- nectors (such as the Shure PS20). See Figure 5 for wiring diagram.

Operational Notes

Input Transformers

The FP24 uses premium Lundahl input transformers with pre- mium magnetic core material to achieve high signal-handling capa- bility, flat frequency response and minimum distortion. Because these transformers provide galvanic isolation from the driving source, they offer superior isolation from the adverse and uncon- trolled environments of field-production. Their high common-mode impedance also provides exceptional common-mode rejection.

Output Circuitry and Tape Output

Each line level XLR output of the FP24 uses a discrete, six-tran- sistor, ªimpedance balancedº output stage. The circuit uses over- sized, high speed transistors to achieve low distortion, robust line driving capability. Pin 2 is driven with signal, and pin 3 is not. (A common misunderstanding is that a ªbalancedº output refers to equal and opposite signals on pins 2 and 3. Correctly, ª impedance balancedº refers to equal impedances from pins 2 and 3 to ground, not equal signal voltages.) To drive unbalanced inputs, pin 3 can be grounded or left unconnected. There is no change in signal level driving balanced or unbalanced inputs.

The FP24's tape output feeds consumer-level devices, such as computer sound cards, DAT or MiniDisc recorders, and cassette recorders. A cable wired with 3.5 mm (1/8 in.) TRS to 3.5 mm (1/8 in.) TRS or 3.5 mm (1/8 in.) TRS to Left/Right phono (RCA) connec- tors will connect the FP24 to such devices.

Using the FP24 as a Mixer

The FP24 can be used as a simple two-channel mixer. Possible applications include:

•Quickly reversing the stereo image of a recording without reconnecting inputs or outputs.

•During set up, checking for mono compatibility by assigning both inputs to the same output.

•Recording dialog in mono.

•Performing ªmix minusº by routing Input 1 to Center and Input 2 to Right. A summed mono signal of both inputs appears at the Right output while only Input 1 appears at the Left output. This is useful for post production processing of Input 1 audio.

Phantom Power

Use one of the two phantom power settings on the FP24 for mi- crophones that require it. Some microphones need the 48-Volt set- ting to avoid a loss of headroom and increased distortion. The 15-Volt setting, however, lengthens battery life, and electret-con- denser microphones rated for operation at 15 V or less generally receive no performance benefit from the 48-Volt setting. Consult your microphone documentation for phantom power requirements.

Dynamic microphones do not require phantom power. A properly connected balanced, dynamic microphone is not affected by the presence of phantom power and does not draw any current. How- ever, poorly or incorrectly wired microphone cable can cause audi- ble artifacts in the microphone signal (phantom power can be an excellent cable tester). It is good practice to turn phantom power off when not needed.

High Pass Filter

To remove excess low-frequency energy in the audio signal, use either of the two high pass (low cut) filter settings on the FP24. Use the 80 Hz position for most applications, such as recording speech, music, and ambient sound. The 160 Hz position is useful for en- hancing speech clarity and reducing wind-noise. The high pass fil- ter is a single pole design, 6 dB per octave.

When possible, equalize at the sound source by microphone selection, placement, use of a windscreen, and onboard micro- phone filtering. Using both the high pass filter on the FP24 and the one on a microphone has an additive effect, increasing the overall slope of the roll-off.

Headphone Monitoring and Tape Return

The three position Tape Return switch on the front panel selects the audio source being monitored:

Center PositionÐProgram audio (normal operation). Monitors the Left and Right outputs of the FP24.

Left and Right PositionsÐSecondary audio source. Monitors audio from the Tape Return input of the FP24. Can be used to verify that signal is reaching cameras and tape machines. Left is locking; right is momentary.

Important: The FP24 can drive headphones to very high levels. Exercise care when monitoring. Reduce the level when the Head- phone Peak LED illuminates.

4