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.
RIGHT SIDE PANEL
Balanced outputs – The main outputs are via transformer balanced XLR connectors and a Hirose 10pin
multiway connector is also fitted to facilitate rapid connection of outputs and monitor returns. The line level is
set on 600 Ω at 0 dBu and +4 dBu for VU metered mixers. The Hirose 10pin connector is wired as follows:
pin 9-10. GROUND
pin 1. + LEFT output pin 5. RIGHT return
pin 2. – LEFT output pin 6. N / C
pin 3. +RIGHT output pin 7. LEFT return
pin 4. –RIGHT output pin 8. N / C
Unbalanced output – A 5pin XLR connector carries an unbalanced stereo output signal – at a level 3 dB
lower than balanced outputs – to feed a recorder, DAT, etc. and monitor returns. The XLR 5pin connector is
wired as follows:
pin 1. GROUND
pin 2. LEFT output pin 4. LEFT return
pin 3. RIGHT output pin 5. RIGHT return
Channel Direct Outputs – 5 pin TA5F connector carries unbalanced direct outputs. Signal is prefader at a
level – 20dBu to feed a recorder and monitor returns with 3.5 jack. TA5F is wired,
pin 5. GROUND
pin 1. CH1 direct output pin 3. CH3 direct output
pin 2. CH2 direct output pin 4. CH4 direct output
Line / mic level switch – The line level at XLR and Hirose connectors can be attenuated by 50 dB to
provide the microphone level.
3.5 mm stereo monitor input jack
Return 1 or 2 selector switch – In position RTN1 the 3.5 jack and Hirose returns are chosen for monitor,
switched to RTN2 the returns of XLR7 will be fitted by the monitoring circuits.
Power supply – The DC power stabiliser of TW mixer has built-in Poly-Fuse to protect the unit. If a
problem occurs that trips this fuse, it will reset after the power supply is diconnected for about 15
seconds.The mixer may be powered by 12 pieces internal AA size rechargeable batteries or an external DC
supply 12-24 Vdc. Fully charged batteries will typically power the mixer for 8 hours at continuous use. The
external XLR 4pin connector is wired as follows:
pin 1., 2. GROUND pin 3. Battery Charge pin 4. External 12-24 Vdc
ADJUSTMENT POINTS
Gain and modulometer adjustment – Connect an AC voltmeter to the Left balanced line output. Set
channel 1 pan switch to L position, turn channel 1 fader fully clockwise, Master potentiometer in 0 dB
position and switch LFA off. Connect an audio generator 1 kHz 0 dBm attenuator –80 dB to Mic 1 Input and
adjust TRIM
AL
in the Left Limiter amplifier to obtain 0 dBu (+4 dBu on VU metered mixers) at the Left
balanced output. Then adjust TRIM
M1
in the Left Modulometer amplifier board to obtain 0 dB on the Left
meter. Cut off the input signal and switch on the Reference Generator . Adjust TRIM
RG
to obtain 0 dB on the
Left modulometer. Repeat for Right output and Right modulometer.
Limiter threshold adjustment – Connect an AC voltmeter to the Left balanced line output. Apply a 1 kHz
signal until the AC voltmeter reading is at the level desired with limiter switched off. Switch on the limiter and
adjust TRIM
LL1
in Left limiter amplifier until the level drops 0.5 dB. Repeat for Right output and Right limiter
trimpot.
SPECIFICATIONS
Inputs
Microphone: four transformerless XLR female
Sensitivity: –75 dBu
Maximum input level: –20 dBu
Microphone power: 48 V, 12 V, T (DIN AB)
Line attenuation: adds 60 dB attenuation before the mic preamp.
Signal to Noise ratio: > 65 dB, Equivalent Input Noise: –125 dBu
Frequency response: 20 Hz - 20 kHz ±2 dB
Harmonic distortion: less than 0.2 %
Low-cut filter: 80/100 Hz / 14 dB octave
Crosstalk isolation, channel to channel: < –65 dB
Outputs
Line: transformer balanced XLR
Line level on 600 Ω 0 dB on the modulometer: 0 dBu
4 on the 1–7 scaling: 0 dBu
0 Vu on the VU scaling: +4 dBu
Four Direct Unbalanced outputs : -20 dBu
Maximum output level: +18 dBu
Internal power: 12 AA size rechargeable batteries
External power: 11–25 Vdc
Power consumption: 90 mA
Dimensions: 255 × 165 × 65 mm (10 × 6.5 × 2.6 in)
Weight: 2 kg (4.2 lbs)
ELECTRONIC COMPONENTS
Kaptárkő u. 11. tel.: +36 1 2466549
Budapest H-1118 fax: +36 1 2480194
HUNGARY e-mail: twelco@chello.hu
www.twelco.hu
Loading...