SCHOEPS MSTC 64 Ug - Handbuch (Seite 18)

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Block Diagram
18
English
Pin assignment of the XLR-5 output con-
nector:
Pin 1: screen (GND)
Pin 2: +phase left channel
Pin 3: –phase left channel
Pin 4: +phase right channel
Pin 5: –phase right channel
1
3
4
5
2
microphone amplifier
acoustic transducer
impedance converter
output stage
DC/DC converter
contr
o
l
EMC filter (RF filter)
scr
een
-phase +phase
XLR-5 connector
3 / 5 1 2 / 4
microphone cable
Phantom powering
U
s
= +48 V
R
s
= 6,8 k
Ω
R
s
= 6,8 k
Ω
preamplifier
,
recor
der or
mixer
+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 11 ** 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(4) or pin 3(5) 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(4) or pin 3(5) of the XLR input.
Given the permitted 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.
* *
**
∼ ∼
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
o-
phone connected, e.g. by opening the connector shell of the cable. The tw
o
voltages (fr
o
m pin 2(4) and pin 3(5) to pin 1) must be identical.
W
ith an MSTC 64 U
a
nd
a
48-V
olt
supply
, they should be about 34
V
olts (minimum = 30 V
olts). For P12 this is 10.6 V
olts (minimum 9.6
V
olts).
3) For P48, use a
SCHOEPS
PHS 48 tester
. Plug it in to the XLR input sock-
et; if the LED glows and stays lit, all is well.
Bottom view
(as the pins are seen)