Specifications

108
Microphone Preamplifier
Technical Specifications:
Inputs
Switchable between two XLR-3F sockets and a special input
for the SCHOEPS KCY Active Cable.
XLR inputs are balanced and transformerless; the 48-Volt
phantom powering is switchable (for subsequent M/S
dematrixing).
Input impedance: 20 kOhms
Frequency range: 20 Hz – 80 kHz (-3 dB)
Recommended minimum sensitivity of microphones at XLR
inputs: 8 mV/Pa
Maximum input level for <0.5% THD:
at 4 dB gain setting: 14 dBV (5V
rms
)
at 20 dB gain setting: -2.2 dBV (780 mV
rms
)
Preamplifier gain settings: 4, 10, 20, 30 or 40 dB
Overall performance specifications of VMS 5 U with
SCHOEPS CMC 6 microphone amplifier and MK 4 capsule
(cardioid):
Maximum sound pressure level at 0.5% THD and equivalent
noise level according as a function of gain:
gain: 4 dB 10 dB 20 dB 30 dB 40 dB
max SPL/dB: 132 132 130 120 109
L
noise
/dB CCIR**: 27.5 26.5 26 26 25.5
L
noise
/dB-A*: 16.5 16 15.5 15.5 15.5
Level indicators: -20 dB, -3 dB
The BALANCE potentiometer permits compensation for dif-
ferences in microphone sensitivity up to 20 dB.
The polarity inversion switch permits rapid change of input
channel assignments in M/S recording, as when changing
between an upright stereo microphone and one that is
hanging downwards.
Outputs
The outputs are impedance-balanced and transformerless,
and are switchable between the amplified microphone
signals and the decoded M/S stereo signals.
Output impedance: 100 Ohms
Maximum output level for <0.5% THD:
18 dBV (8 V
rms
)
Recommended load impedance: 2 kOhms or greater
Headphone output
Switchable; either the amplified microphone signals
(=left / right for A/B recordings, or mid / side for M/S) or
the de coded M/S stereo signals can be monitored.
Headphone impedance: 32 – 2,000 Ohms
Headphone socket: 1/4" stereo phone jack
Filters
An infrasonic filter (20 Hz, 18 dB/oct.) is permanently active.
In addition, a low-cut filter (150 Hz, 6 dB/oct.) can be
switched on.
The upper frequency limit is 80 kHz.
Powering
An internal filter / regulator circuit which generates and sta-
bilizes the supply voltages permits a wide range of input
voltages (5.5 V to 15.5 V).
Operation with internal batteries (possibly rechargeable)
Number and type of cells: 6 × AA (also called LR6)
Recommended primary cell type: Alkaline
Recommended rechargeable cell type: NiMH
A user-replaceable fuse protects against reversing the polar-
ity of the batteries.
Battery life with alkaline cells: ca. 8.5 hours
Battery life with rechargeable batteries:
ca. 3 hours (700 mAh NiCd)
ca. 5 hours (1100 mAh NiMH)
ca. 5.5 hours (1300 mAh NiMH)
ca. 7 hours (1600 mAh NiMH)
ca. 12 hours (3400 mAh gelled lead-acid battery (external))
A voltage indicator displays the battery voltage within the unit.
A warning LED will begin to blink if the voltage falls
beneath a critical value (time remaining at that point with
1300 mAh rechargeable batteries: at least 10 minutes).
The unit will shut itself off automatically to help prevent
damage from draining the batteries completely. The unit
resumes operation only after the on / off switch is used.
External powering
An appropriate AC power adapter is available (model VMS
5 DC-W). Other adapters offering a regulated or unregu-
lated output voltage of 6 Volts DC (at 500 mA) to 15
Volts DC (at 250 mA) can also be used. Under no circum-
stances should an open-circuit voltage of 16 V be
exceeded; otherwise a fuse inside the VMS 5 U will blow.
Coaxial socket, 5.5 / 2.1 mm diameter
Reverse polarity will not damage the unit, though it will not
operate.
If external powering is present, any internal batteries are
automatically disconnected (indicated by yellow LED
“EXT.”). This protects the batteries from being dis-
charged unintentionally.
The battery voltage indicator displays the level of any exter-
nal powering.
External powering with outboard rechargeable battery:
nominal 6 – 12 V; we recommend gelled lead-acid bat-
teries (6 V, 3400 mAh type = 12 hours of operation).
Parallel operation of a VMS 5 U along with one or more
other pieces of equipment from a single power supply is
generally possible, because of the internal voltage regula-
tion.
Robust, black aluminum case.
Overall measurements: (W × H × D):
162 mm × 60 mm × 172 mm
(approximately 6-2/3" × 2-1/3" × 6-3/4")
Weight (with batteries): 1.1 kg
(approximately 2 lb. 7 oz.)
*IEC 61672-1, **IEC 60268-1