TW Electronic Components LP4 STXi User Manual

ELECTRONIC COMPONENTS

LP4 STXi

USER MANUAL

TW LP4 STXi (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

Ÿ 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.

Ÿ 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.

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

Ÿ 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.

Ÿ 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.

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

Ÿ 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

Ÿ 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.

Ÿ Battery check pushbutton
Ÿ 6.3 and 3.5 mm phone jacks
Ÿ 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.

Ÿ Phones volume control – Output voltage into 50 Ω adjustable from 20 to 500 mV.
Ÿ Limiters on / off switches – The four individual 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.

Ÿ 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.

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

Ÿ Low -cut filter switches – Low frequency attenuation is 14 dB / octave at 100 Hz.
Ÿ 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.

Ÿ Channel gain controls
Ÿ Pre -Fade Listen pushbuttons – Each channel can be checked by monitoring. Output audio signal

is not interrupted when the PFL pushbutton is activated.
Ÿ 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.
Ÿ 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.

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