Manual

SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [e-mail]
Block Diagram of the CCM Compact Microphones
7
Technology
microphone amplifieracoustic
transducer
Pin assignment of the XLR-3M output con-
nector of CCM microphone amplifiers:
Pin 1: screen (GND)
Pin 2: +phase
Pin 3: –phase
Bottom view
(as the pins are seen)
1
2
3
Impedance converter
Output stage
DC/DC converter
Regulator
EMI filter
3 1
Screen
-Phase
+Phase
XLR-3 Connector
2
3 1 2
3 1 2
Microphone cable (adapter cable Lemo/ XLR-3M
Phantom powering
U
s
= +48 V
R
s
= 6.8 kΩ
R
s
= 6.8 kΩ
Preampli - fier, recorder or mixing desk
*
*
**
**
∼
∼
screen
-phase
+phase
XLR-3 connector
XLR-3 connector
and between 15 and 21 mA DC for P12. Note: Well-designed phantom power supplies must tolerate at least a temporary short circuit without damage; an unbalanced connection (which is occasionally necessary) would cause the same current to be drawn. To be safe, however, do not leave the short circuit in place longer than necessary. 2) Measure the DC voltages on the modulation leads with a micro- phone connected, e.g. by opening the connector shell of the cable. The two voltages (from pin 2 and pin 3 to pin 1) must be identical. They should be about 34 Volts (minimum = 30 Volts). For P12 this is 8.3 Volts (minimum 7.3 Volts). 3) For P48, use a SCHOEPS PHS 48 tester. Plug it in; if the LED glows and stays lit, all is well.
+Phase: an excursion of the diaphragm towards the back electrode (posi- tive pressure phase) leads to a positive signal at this pin *Matched (i.e. matching tolerance of only 0.7%), see page 5 ** Here are three simple methods for verifying correct phantom powering.
These measurements should be made at an unused input. Reduce the channel gain to the minimum to protect the loudspeakers, etc. If micro- phones are connected to other inputs at the same time, no substantial difference should occur in the results.
1. Measure the open-circuit voltage between ground (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, measure the short-circuit current between ground (pin 1) and either pin 2 or pin 3 of the XLR input. Given the permitted tolerances, this current should be between 5.9 and 8.5 mA DC for P48,