Manual

SCHOEPS GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: [phone] · Fax: [phone]
www.schoeps.de · [e-mail]
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
Screen
-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 kΩ
R
s
= 6.8 kΩ
∼
∼
Preampli - fier, recorder or mixing desk
4
1 2 3
*
*
**
∼
∼
3 1
Impedance converter
screen
-phase
+phase
XLR-3 connector
XLR-3 connector
Pin 1: screen (GND) Pin 2: +phase Pin 3: –phase Bottom view (as the pins are seen)
1
2
3
mitted tolerances, this current should be between 5.9 and 8.5 mA DC for P48, 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, don't leave the short circuit in place longer than necessary. 2) Measure the DC voltages on the modulation leads with a microphone 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. With a CMC 5 or CMC 6 and a 48-Volt supply, they should be about 34 Volts (mini- mum = 30 Volts). For P12 this is 8.3 Volts (minimum 7.3 Volts) with a CMC 3, and 9 Volts (minimum 8 Volts) with a CMC 6.
+Phase: An excursion of the diaphragm towards the back electrode (posi- tive pressure phase) leads to a positive signal at this pin. *matched pair; see page 5 ** Here are two simple methods for verifying correct phantom powering.
These measurements should be made at an unused input. Reduce the channel gain to protect loudspeakers, etc. If microphones 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 per-
Nominal voltage gain: standard CMC amplifier: -2 dB, ”+5 dB” version: +3 dB.