TW LP4 S User Manual

ELECTRONIC COMPONENTS

LP4 S

USER MANUAL

TW LP4S (Location Production) stereo microphone mixer is a compact

portable four-channel unit designed for electronic news gathering (ENG)

quality sound mixing in a motion picture or television film.

LEFT SIDE PANEL

 Balanced channel inputs – four electronically balanced circuits (transformer balanced is optional) in
phase with one another. XLR connectors should be wired as pin1 ground, pin2 +phase signal and pin3 –
phase signal.

 Microphone powering selector switches – The input sensitivity in position D is DYN 200 = 0.2 mV and
no power. Selected 48, 12, T, mic powering, 10 dB of attenuation is automatically introduced, considering the
sensitivity of condenser mics.

 Phase reverse switches – Intended to compensate for a phase error due to wiring or mic placement.

 Phantom on / off switch – The current consumption of the phantom power supply is 13 mA. Phantom

power supply may be switched off (only if using dynamic, wireless of T powering mics) to increase the
lifelength of the internal batteries between two chargings.

 Attenuation switches – The gain of the mic preamplifiers may be decreased by –10 dB in position D. In
positions 48, 12 and T the attenuation is –13 dB.

 Mic / line level switches – Selects mic or line to add –60 dB attenuation before the mic preamplifiers.

 Optional NP1 Battery Holder – The switched mixer supply is derived either from the internal AA batteries

or from NP1 battery depending on the position of the panel side switch.

FRONT PANEL

 Modulometers – Continuous lighting, peak reading, BBC 1-7, dB or VU scaling, built-in red LEDs indicate
when the gain reduction is occurring with the limiters switched on.

 Battery check pushbutton

 6.3 and 3.5 mm phone jacks

 Monitor selector switch – ST stereo. L+R sum signals, phase check, MS stereo equivalent Left.

L–R difference signals MS stereo equivalent Right. MS matrix, MS stereo equivalent. R right channel. L left
channel.

 Phones volume control – Output voltage into 50 Ω adjustable from 20 to 500 mV.

 Limiters on / off / link switch – The limiters have fast attack time (less than 1 msec) and a slow release

time to smooth operation. Two red LEDs are built in the meters to indicate when the limiters are selected and
gain reduction is occurring. Threshold is internally set to +6 dBu at the balanced output. To adjust the
threshold for a value different from the supplied +6 dBu, see page ADJUSTMENT POINTS.

 Reference generator switch – 1 kHz sine wave signal is fed to both left and right outputs, its level can be
controlled by the Master control.

 Slate microphone – It can be used either for identifying recorded segments or as an emergency field
microphone.

 Low-cut filter switches – Low frequency attenuation is 14 dB / octave at 80 and 160 Hz.

 Pan switches – Assign selected input signal to Left or Right output. In M position, equal amount of signal

is sent to Left and Right outputs. The S position of Pan switches 1 and 3 assigns Channels 1–2 and 3–4 as
stereo pairs controlled by Channel 1 and 3 Faders respectively.

 Channel gain controls

 Pre-Fade Listen pushbuttons – Each channel can be checked by monitoring. Output audio signal is not

interrupted when the PFL pushbutton is activated.

 EE / RTN12 switch – A two-position switch selects the direct outputs from the mixer or the return 1 and 2
as a signal source for the monitoring.

 Master – The fader sets the gain of both Left and Right legs and has +6 dB of gain in hand with the
nominal 0 dB gain position marked.

 PWR LED – A red LED lights to indicate power is on. Flashes when voltage is 11.5 Vdc or less.

 Power switch – In position EXT the mixer will be powered by an external DC supply and in BATT by the

internal batteries. Batteries should be recharged with the switch in EXT position.