Schoeps VSR 5 U User manual

VSR 5 U
Microphone Preamplifier
Operating Manual

2SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]

3
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]

4
Contents
Contents Page
Introduction 5
The Power supply 5
The Signal Path and Operating controls 6
Notes on EMC, Ground Lift Switch 9
Specifications 12
Safety Information 13
Warranty, EMC, Declaration of Conformity 14
© 2009 by Schalltechnik Dr.-Ing. SCHOEPS GmbH
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]

5
Introduction / The Power Supply
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]
Two independent outputs, each with its own
circuitry, are provided for each channel.
Behind the robust aluminum front panel,
the chassis is stainless steel which guarantees
high mechanical stability and resistance to
environmental influences. It also shields the
circuitry from electrical and electromagnetic
fields.
The Power Supply
The power supply uses a built-in socket con-
nector for a standard, three-wire AC power
cord (IEC/EN 60320
C14).
The operating
voltage is set to
230 Volts at the
time of delivery.
If needed, the
power supply volt-
age can be changed
on the rear panel
either by hand or with a screwdriver.
The power on/off switch is also on the rear
panel. LEDs in the front-panel switches signal
that the unit is powered on. Depending on
their settings, the LEDs will be lit either
dimly (”off”) or brightly (”on”).
The internal power supply uses three gen-
erously-sized toroidal transformers. The
required DC operating voltages are provided
by linear circuitry.
Power-Line Fuses
The power-line fuses of the VSR 5 are soldered
to the circuit board of the power supply, and
are not externally accessible. A burned-out
fuse would generally indicate a defect in one
or more components, and fuses should thus
be replaced only after a careful check of the
unit by qualified service personnel. If a fuse
burns out during the warranty period, the
Dear customer,
Thank you for choosing the SCHOEPS VSR 5
– a very high-quality, low-noise, low-distor-
tion stereo microphone preamplifier.
Its special features: The central gain element
in each channel is a differential amplifier with
current feedback. The module used in the
VSR 5 was inspired by the ultra-low-noise
Valley People ”Trans-Amp LZ,” developed in
the 1970s.
The two channels of the VSR 5 are com-
pletely separate from one another. Thus there
are two each of all the operating controls.
The gain is selected by means of a 21-step
rotary control which can be set in 3 dB steps
from unity through 60 dB.
Each channel has a pushbutton switch for:
– phantom powering
– polarity inversion
–mute
– a 40 Hz low-cut filter
– an 80 Hz low-cut filter
– a 120 Hz low-cut filter
All the pushbutton switches have LEDs to
indicate their status. When the unit is turned
on and the pushbutton switches are not
activated, the LEDs glow at low intensity.
When phantom powering is turned on or
off, the outputs are muted for about four
seconds.
Output levels are indicated in 3-dB steps by
means of a 20-level LED meter. The display
thus has a range of 57 dB. A ”clip” LED lights
at signal levels above +20 dBu. Since this is
ca. 8.5 dB below the maximum output volt-
age of the preamp, clear warning is given
before overload occurs. The carefully chosen
gain parameters of the VSR 5 also ensure that
this LED would light in the event of any pos-
sible overload of the input circuit.
The electronically balanced inputs and out-
puts are on the rear panel.

The Signal Path and Operating Controls
6SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]
whenever phantom powering is turned on
or off, as indicated by a red LED in the
”Mute” switch.
The status of the ”P48” switch is automat-
ically stored. When the preamplifier is turned
on, phantom powering will be activated if it
was on when the unit was last turned off.
Note: When phantom powering is turned
on, pins 2 and 3 of the respective input socket
will carry 48 Volts DC. If this should be con-
nected to a line-level input, damage can be
caused.
Mute Switch
The output of each channel can be muted
for any length of time by pressing its Mute
switch. The switch is illuminated in red as long
as this function remains activated. The status
of this function is automatically stored when
the preamp is powered off.
Polarity Switch
When recording with multiple microphones,
e.g. miking percussion such as a snare drum
from above and below simultaneously, signal
cancellation can occur due to the conflicting
phase relationships. Problems can also occur
when microphone or cable connectors are
incorrectly wired.
A simple test (and also a solution) is pro-
vided by the ”Polarity” switch, which allows
the user to invert the signals of the corre-
sponding channel.
When activated, the LED in the switch will
glow brightly.
balanced
micro-
phone
output
VSR 5 input socket The plug housing should not be connected to
the cable shield (pin 1), since this can cause a
ground loop. For best protection from electro-
magnetic disturbance we recommend the use
of SCHOEPS' special XLR-3 cable, e.g. K EMC 10 U
(10 meters).
+phase
-phase
screen
unit must be returned to the factory or its
warranty will be voided.
The Signal Path and Operating
Controls
Inputs
The XLR sockets of the electronically balanced
inputs are on the unit's rear panel, labeled
”Balanced Input”. The inputs accept balanced
or unbalanced audio signals.
The contact assignment follows the inter-
national standards:
Pin 1 = Ground
Pin 2 = (+) Phase
Pin 3 = (-) Phase
Phantom Powering
Most condenser microphones require phan-
tom powering in order to operate. The VSR 5
supplies this at its inputs. It can be turned
on and off with the front panel ”P48” switch.
The open-circuit voltage is 48 Volts in keep-
ing with international standards, provided
via a pair of 6.8 kΩresistors on pins 2 and 3
of the input sockets.
In most conventional microphone pream-
plifiers, turning the phantom powering on
or off causes a change in low-frequency
voltage at the output, which can be audible
as a loud noise, and can cause harm to
other equipment. In the SCHOEPS VSR 5 an
automatic muting circuit avoids this prob-
lem. The circuit activates for 2.5 seconds
12
3
X
Connecting to the inputs of the VSR 5

Operating Controls
7
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
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This function is carried out by means of
high-quality relays rather than placing any
additional electronic components in the sig-
nal path.
Gain Control
The gain of each channel can be set in 3 dB
steps from unity to 60 dB by means of the
21-position rotary gain control on the front
panel. The precision of this setting is within
±0.3 dB throughout its entire range.
Low-Cut Filters
To remove inaudible frequencies as well as
disturbing noise such as popping, wind or
microphone handling noise without affecting
the desired signal, the SCHOEPS VSR 5 offers
three switch-selectable low-cut filters with
40 Hz, 80 Hz and 120 Hz cutoff frequencies.
The currently active cutoff frequency is indi-
cated by the bright white illumination of the
corresponding switch.
Only one filter per channel can be active at
a time. The frequency can be changed simply
by pressing the corresponding switch. Each
filter can also be deactivated by pressing its
Front-panel features of the VSR 5 with phantom powering enabled and a microphone con-
nected, normal polarity, outputs muted, and 80 Hz selected as the cutoff frequency of the
low-cut filter.
Phantom powering is turned off.
Phantom powering is turned on, but no
microphone is connected.
Phantom powering is turned on and a
microphone is connected.

Note:
During production, the reference level of the
0 dB LED is set to +6 dBu.
”Clip” Indicator
The red ”Clip” LED has a fixed reference
voltage. It begins to blink at levels above ca.
+20 dBu, thus giving a warning before there
is any possible overload.
Outputs
The SCHOEPS VSR 5 is equipped with two
separate electronically balanced XLR outputs
per channel.
The gold-plated XLR output sockets are on
the rear panel of the unit. In accordance
with international standards, the layout is:
Pin 1 = Ground
Pin 2 = (+) Phase
Pin 3 = (–) Phase
Note: The VSR 5 has floating, servo-balanced
outputs. Thus if either pin 2 or 3 is grounded,
the output levels will remain the same as in
balanced operation.
Operating Controls
8SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]
button a second time. The filter selection is
stored when the preamplifier is turned off,
and is set automatically the next time the unit
is turned on.
Level Indicator
The signal level indicator of the VSR 5 con-
sists of 21 LEDs including a ”Clip” LED.
The level is indicated in steps of 3 dB. The
range from -48 to -15 dB is shown in green,
the range from -12 to -3 dB in yellow, and
the LEDs for 0 to +9 dB are red, as is the
”Clip” LED.
A full-wave DIN PPM peak detector drives
the display with an attack time of <10 ms
and a decay time of 0.5 seconds per 20 dB.
Here the 80-Hz low-cut filter has been acti-
vated.
Do not connect the plug connector's
housing to pin 1.
Do not connect the plug connector's
housing to pin 1.
In this case pin 3 must be connected
to pin 1 (ground), since pins 2 and 3 of
the output from the VSR 5 are floating.
VSR 5 output socket
VSR 5 output socket
balanced
input
unbalanced
input
Connecting the inputs and outputs of the VSR 5
21
3
X
21
3
X

Notes on EMC, ”Ground-Lift” Switch
Notes on EMC (Electromagnetic
Compatibility)
This section is admittedly rather long in pro-
portion to the rest of the manual. Please be
assured that, as a rule, the VSR-5 will not
have problems with interference even if you
don't memorize all the details which we are
about to present. However, in the rare event
that a problem with hum or radio-frequency
interference does occur, we want to offer
enough information to be of real help.
A summary of how to proceed:
1. Set the Ground Lift switch to the ”Hi-Z”
position. That setting will prevent interfer-
ence in most circumstances, and is recom-
mended as the default.
2. Use microphone cables that make no con-
nection between the XLR-3M connector
housing and pin 1. Only the shield of the
cable should be connected with pin 1 at
either end of the cable. For best results,
use the SCHOEPS cable K EMC_U.
3. Whenever the outputs of the VSR 5 are
connected to one or more items of other
equipment, only one unit should have a
direct connection between its circuit ground
and AC safety ground. Thus, if necessary,
a ground lift switch on one of the units
should be set to the ”ground” position.
(This does not apply to battery-operated
equipment, nor to AC-operated equip-
ment that is completely isolated from the
electrical safety ground and carries the
symbol .)
4. Power all equipment that is connected to
the VSR 5 from one common AC power
outlet.
Detailed description
In the development of the VSR 5, emphasis
was placed on first-rate audio characteristics
but also on a corresponding degree of immu-
nity to radio-frequency interference (RFI).
Filters for this purpose have been built into
the inputs and outputs, but these protective
measures can reach their full effect only if
suitable cables are used.
To guarantee the best possible protection
from RFI we recommend using special
SCHOEPS XLR-3 microphone cable such as
K EMC 10 U (10 meters) oder K EMC 20 U
(20 meters). This cable is distinguished by:
– being RF-proof due to its high degree of
shield coverage
– conduction of any RF picked up by the
shield to the chassis of the unit to which
the cable is connected, by means of con-
densers in the output plug – not through
the connection of pin 1 with the connector
housing; this avoids ground loops
– small diameter
– robustness
– non-twisting (important when hanging
microphones)
– flexibility even in cold weather
”Ground-Lift” Switch
In conventional XLR-3 cables pin 1 and the
plug housing are often connected together.
This can offer a certain amount of protection
from electromagnetic fields. In that case the
setting of the ”Ground-Lift” switch is imma-
terial since it is bridged by the connection in
the cable plug. But the connection of pin 1
with the connector housing can create
ground loops which can cause hum when
several pieces of equipment share the same
protective AC ground. (What a ground loop
is and what causes it is shown on the fol-
lowing page.) Thus the option exists to sepa-
rate the circuit ground from the chassis
ground by setting the ”Ground-Lift” switch
to the ”LIFT” position. For this to have any
effect, however, the connection in the XLR
plug of the cable between pin 1 and the
9
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]

SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]
10
”Ground-Lift” Switch
Unit without
ground-lift switch
Conductive chassis Conductive chassis
Circuit
ground
Hum current
Connection by
way of the house
AC safety ground
VSR 5 U
12
2
33
Connector
housing
Circuit
ground
I
Cable shield
The red dashed line is a ground
loop. As in the windings of a
transformer, magnetic fields--
either from power supply trans-
formers or due to differences in
chassis potential among con-
nected items of equipment –
cause current to flow at 50 or
60 Hz.
C*
Ground-lift
switch
”GND” ”LIFT”
”HI-Z”
1
* Bypass capacitor for RF; the SCHOEPS
K EMC _U cable also has bypass capa-
citors in its XLR plug
connector housing must be interrupted, and
this can again lead to problems with RFI.
To avoid both RFI and ground loops at the
same time, we recommend the use of the
SCHOEPS K EMC _ U cable. In the connectors
of this cable there is no DC connection
between pin 1 and the housing; thus no
ground loops can occur. RFI on the other
hand is conducted to chassis ground through
condensers built into the plug connector.
This provides RF protection despite the lack
of a DC connection from pin 1 to the chassis.
So that the ”Ground-Lift” switch does not
create a ground loop, do not set it to the
”GND” position when this type of cable is
being used. The ”HI-Z” position of the
Ground-Lift switch is designed to bridge the
difference in ground potential among pieces
of equipment that are connected to power
outlets some distance apart, without causing
hum problems.
Safety is maintained by keeping the chassis
of the VSR 5 connected to AC safety ground
regardless of the ”Ground-Lift” switch setting.
Avoiding ground loops
The greater the size of the loop encompassed
by the relevant equipment, the greater the
effective AC magnetic field radiated by trans-
formers or electrical conductors, and the
stronger the induced hum is likely to be. Thus
to the extent possible, all interconnected
equipment that uses three-wire AC power
cords should be powered from the same out-
let. This will minimize the ground loop area
and thus the resulting hum.
The origin of ground loops

11
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Notes on EMC
Cables among the various pieces of equipment
should be arranged so that the loop they form
has the smallest possible area.
As a third tactic, the signal cables of all audio
equipment should be kept as far as possible
from sources of magnetic fields (transformers,
high-current power cables).
The ”Ground Lift” switch will have no effect
if pin 1 of the microphone cable is connected
to its connector housing. In that case a ground
loop will be created via the shield contact of
the unit's input socket, since this contact is
connected to the chassis and thus to the AC
safety ground.
If hum problems occur, the best approach
is to reduce the extent of any ground loop.
Should this not help, any existing connection
between pin 1 and the plug connector hous-
ing of the microphone cable should be cut.
But please be aware that doing this can lead
to radio-frequency interference, especially if
the RF is not bypassed to the chassis by way
of a capacitor from pin 1 immediately at the
input.
A further possible cause of hum
Please note that strong hum can occur if the
input of the VSR 5 is left ”open” (i.e. neither
a microphone nor any other item of equip-
ment is connected to it) while the Ground-Lift
switch is in the ”LIFT” position. This hum does
not represent a defect, but results from the
fact that the circuit ground is not connected
to the chassis under these conditions, which
limits the ability of the chassis to act as a
shield even though it is connected to the AC
safety ground. The hum will disappear if any
of the following occurs:
a) if pin 1 of any cable connected to the VSR 5
is also connected to its connector housing;
b) if the VSR 5's Ground-Lift switch is set to
”Ground”;
c) if an item of equipment with a direct con-
nection between its circuit ground and its
AC safety ground is connected to the VSR 5;
or
d) double-insulated (”Class II”) equipment
( ), if a cable with an extra ground wire
is connected.

Specifications
12 SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]
Inputs: 2, balanced, electronically floating
Phantom powering: +48 VDC (P 48*); can be switched off
Resistances: 2 × 6.85 kOhms
Maximum current: 10 mA (according to standards)
Minimum current at which LEDs indicate a microphone at an input: 1.7 mA
Input impedance: 8 kOhms
Input CMRR** at 60 dB gain: > 90 dB at 1 kHz (for typical values see Fig. 1)
> 80 dB at 15 kHz
Max. input level: 25.4 dBu (23.2 dBV) at 0 dB gain, f = 1 kHz
Gain adjustment: 0 dB ... 60 dB in steps of 3 dB
Gain accuracy: ±0.3 dB
Low cut filters (-3 dB): 40 Hz, 80 Hz, 120 Hz at 12 dB/oct.
or ”off” (see Fig. 2)
THD+N at 1 kHz: 0.0006% at 30 dB gain and 27.5 dBu output
level (1 dB below clipping) into 100 kOhm
load
(see Fig. 3)
Noise (input terminated with 200 Ohms; gain: 60 dB, referred to input):
-127.8 dBu (-130.0 dBV), unweighted, RMS
-130.6 dBu (-132.8 dBV), A, RMS***
-117.4 dBu (-119.6 dBV), CCIR-1k, Q-peak****
Frequency range (gain: 30 dB): 12 Hz ... 90 kHz (±0.1 dB)
2.5 Hz ... 400 kHz (-3 dB)
Inter-channel phase difference: 0.0° at 5 Hz
0.0° at 50 Hz
0.0° at 1 kHz
0.0° at 10 kHz
+0.20° at 200 kHz
Slew rate of the ”Core SVM”: 10 V/µs at 30 dB gain
RF filter range (in- and outputs): 3 MHz – 1 GHz, see Fig. 4
Max. output level: 28.5 dBu (26.3 dBV)
Outputs: 2 × 2, balanced, electronically floating
Output impedance: 50 Ohms
Output CMRR*: ca. 60 dB (20 Hz – 20 kHz)
Meter range: -48 dBr ... +9 dBr (adjustable)
clipping LED lights up at +15 dBr
Power supply: 94 ... 125 VAC / 185 ... 250 VAC, 50 – 60 Hz
Power consumption: 10 VA
Dimensions (19", 2U): 485 mm (w) × 60 mm (h) × 195 mm (d)
Weight: 4.70 kg, 10.34 lbs
Case: stainless steel, aluminum
Front: gray Nextel finish; front panels: stainless steel
10MHz 100MHz 1GHz
dBr
Fig. 4, noise floor and level of RF interfer-
ence at 10 dBm and 80% AM modula-
tion at the inputs
dBr
Fig. 3, distortion @ 1 kHz, gain= 30 dB,
1 dB below clipping
10 100 1k 10k 40kHz
Fig. 2, Frequency response with 40, 80 and
120 Hz cut-off frequency
dBr
10 100 1k 10k 40kHz
dBr
Fig. 1, Common-mode rejection ratio
10 100 1k 10k 40kHz

Safety Information
Safety Information
Please observe the following safety advice:
Water, Liquids, Moisture
Operation of the unit near water or other
sources of liquids should be avoided.
Please make certain that the unit cannot
fall into liquids or that liquids cannot enter
the openings in the unit's housing.
The unit should not be operated in spaces
with high humidity, especially condensing
humidity.
Operating Voltage
The unit may only be operated with the AC
line voltages specified in these operating
instructions (94 ... 125 VAC / 185 ... 250
VAC, 50 – 60 Hz).
Electrical Safety Ground
Please make certain that the unit is connect-
ed to electrical safety ground in accordance
with regulations.
AC Power Cable
Make certain that the AC power cable is in
good condition. Arrange the AC power cable
so that it will not be damaged and so that it
does not cause accidents.
The unit is shipped with a three-wire AC
power cable with a German Schuko plug.
On request a three-wire AC power cable for
North American use can be provided instead.
In some countries the unit must be used
with a customer-provided AC power cable.
Service / Repair
None of the internal parts of this unit require
maintenance.
Any needed repairs should be carried out
only by qualified service personnel.
To preserve your warranty rights, all repairs
during the warranty period should be carried
out only by SCHOEPS or its authorized repre-
sentatives.
Caution: There is a risk of electrical shock if
the unit is opened. Always disconnect from
AC power first!
13
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14 SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
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Electromagnetic Compatibility
(EMC)
This equipment meets international specifica-
tions as described in the Declaration of
Conformity below. It does not emit interfe-
rence. It can be used in environments in
which interference exists, even if that redu-
ces its effectiveness for its intended use. That
is, the unit's functioning may be affected in
the worst case by electrical, magnetic or
electromagnetic fields, but it will not be
damaged. Operation of this equipment in
surroundings with high electromagnetic field
strengths (e.g. near transmitters) should be
avoided.
Declaration of Conformity
– CE-Mark
The CE-mark guarantees that all products
conform to relevant standards approved by
the European Community. The products
described in this User Guide comply with
current, relevant standards when used with
cables from SCHOEPS.
Relevant directives:
EMC Directive: 89/336/EEC, amended by
92/31/EEC and 93/68/EEC
Relevant standards:
EN 55 103-1, -2 and those which are referred
to by them.
Warranty
We guarantee our products for a period of
twenty-four months, except for batteries.
The guarantee period begins on the date of
purchase.
Please provide your bill of sale in all cases
as proof of guarantee; without it, repairs will
be undertaken only at the owner's expense.
We reserve the right to satisfy all warranty
requirements regarding defects of workman-
ship or materials by means of repair or par-
tial or complete replacement of the product,
at our sole discretion.
Excluded from this guarantee are defects
due to misuse (e.g. incorrect operation;
mechanical damage), abuse or “Acts of
God.” This guarantee is nullified in the event
of tampering by unauthorized persons or
agencies.
To secure your rights under this guarantee,
send the product with proof of purchase
and a precise description of the malfunction,
at your expense, either to SCHOEPS (if you
are a customer in Germany), or to our repre-
sentative (if you are a customer outside of
Germany).
Prior to sending your defective product for
repair, please contact your local dealer or
distributor for instructions. In exceptional
cases you can, by prior arrangement with
SCHOEPS, send the product directly to us
from a foreign country. However any return
shipment must then be prepaid; this tends
to cause delays, especially for non-warranty
service. Full payment must be made before a
repaired item can be returned to the cus-
tomer.
This guarantee does not affect any con-
tractual agreements which may exist
between the buyer and seller of the equip-
ment.
This guarantee is world-wide.
Warranty, EMC, Declaration of Conformity

15
SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [email protected]

Subject to change without notice.
Not responsible for errors or omissions.
091101
Technik
Schall
SCHOEPS GmbH
Spitalstraße 20
D-76227 Karlsruhe (Durlach)
Tel: [phone]
Fax: [phone]
www.schoeps.de
[email protected]