SCHOEPS MK xx - Manual (Page 8)

SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: +49 721 943 20-0 · Fax: +49 721 943 2050
www.schoeps.de · [email protected]
Block Diagram of the CMC 3, 5, 6 Microphone Amplifiers
Microphone Amplifiers
8
Capsule MK --
Capsule MK --
Impedance converter
Output stage
DC/DC converter
Regulator
EMI filter
e.g. cable KC -- or tube RC -- Active Accessories:
3 1 4 2
3 1
3 1
3 1
4 2
3 1 Scr
een
-Phase +Phase
XLR-3 Connector 2
3 1 2
3 1 2
Center contact ( ) Inner ring (0 V) Middle ring (+60 V) Outer ring (+6,2 V)
Microphone cable
Microphone Amplifier CMC --
Phantom powering
U
s
= +48 V
R
s
= 6.8 k
Ω
R
s
= 6.8 k
Ω
∼ ∼
Preampli
-
fier
,
recorder or mixing desk
4 1 2 3
* *
**
∼ ∼
3 1
Impedance converter
+Phase: An excursion of the diaphragm towar
ds the back electr
ode (posi-
tive pr
essur
e phase) leads to a positive signal at this pin.
*matched pair; see page 5 ** Her
e ar
e thr
ee simple methods for verifying corr
ect phantom powering.
These measur
ements should be made at an unused input. Reduce the
channel gain to pr
otect loudspeakers, etc. If micr
ophones ar
e connected
to other inputs at the same time, no substantial dif
fer
e
nce should occur
in the r
e
sults.
1. Measur
e the open-cir
cuit voltage between gr
ound (pin 1) and either
pin 2 or pin 3 of the XLR input. Given the permitted tolerances, this voltage should be between 44 and 52 VDC for P48, and between 11 and 13 VDC for P12. Then, measur
e the short-cir
cuit curr
ent between
gr
ound (pin 1) and either pin 2 or pin 3 of the XLR input. Given the per-
mitted tolerances, this curr
ent should be between 5.9 and 8.5 mA DC
for P48, and between 15 and 21 mA DC for P12.
scr
een
-phase +phase
XLR-3 connector
XLR-3 connector
Pin 1:
scr
een (GND)
Pin 2:
+phase
Pin 3:
–phase
Bottom view (as the pins ar
e seen)
1
2
3
Note: W
e
ll-designed phantom power supplies must tolerate at least a
temporary short cir
cuit without damage; an unbalanced connection
(w
h
ic
h
i
s
o
cc
a
sionally necessary) would cause the same curr
ent to be
d
ra
w
n
.
To
be safe, however
, don't leave the short cir
cuit in place longer
than necessary
.
2) Measur
e the DC voltages on the modulation leads with a micr
ophone
connected, e.g. by opening the connector shell of the cable. The two voltages (fr
o
m pin 2 and pin 3 to pin 1) must be identical. W
ith a CMC 5
or CMC 6 and a 48-V
olt supply
, they should be about 34 V
olts (mini-
mum = 30 V
olts). For P12 this is 8.3 V
olts (minimum 7.3 V
olts) with a
CMC 3, and 9 V
olts (minimum 8 V
olts) with a CMC 6.
3) For P48, use a
SCHOEPS
PHS 48 tester
. Plug it in to the XLR input socket;
if the LED glows and stays lit, all is well.
Nominal voltage gain: stan- d
a
rd
CMC amplifier: -2 dB,
”+5 dB” version: +3 dB.