10
The Earth / Grounding Concept
General GROUND-LIFT Jumper (accesible from the rear of the case):
Ex works this jumper is plugged to
GND/GROUND
position.
The internal ground potential, which is normally connected to the external earth reference at this point may be
lifted with the aid of this jumper. As a result the interconnection for DC voltages and lower frequencies (< 160 Hz)
will be cut. Higher frequency are allowed to find their way to earth potential through the RC filter. The LIFT
position may be helpfull when e. g. because of different ground/earth potentials hum or jitter is generated.
Unfortunately there is no general recommendation how to solve hum and jitter problems - or even minimize them.
The best way to succeed is to check different options !! In case of balanced cables it should always been verified
if the shield of the cable is connected to the body of the XLR connector. The connector is ALWAYS connected to
Earth potential when plugged in !!
Concerning ANALOG inputs and outputs, the relationship between ground and earth may be modified. In any
case the electrical security is ensured, because the earth conductor is always connected to the enclosure !!
XLR GROUD-LIFT Jumper (accesible from the inside, follow the SECURITY INSTRUCTIONS !! ):
G(ROUND):
Ex works all jumpers are set to
G(ROUND)
position. Pin 1 is connected to the internal ground
reference. High frequency interferences are deflected to the case via a 100 nF capacitor.
L(IFT):
The interconnection between Pin 1 and ground is open. High frequency interferences are deflected
to the case via a 100 nF capacitor. This jumper position is useful when the unit is equipped with
transformers !!
C/ASE):
Pin 1 is connected to the case, the 100 nF capacitor is bridged. This jumper position may be varied
together with the
General GROUND-LIFT jumper
.
Please note that with jumpers in LIFT or GROUND position EMC problems might occure.
Theses are in the field of the user´s responsibility !!!!
PHONE-AMP F399 GROUND CONCEPT / SIMPILIFIED BLOCK CIRCUIT
15/25/30 V
G(round)
G(round)
G(round)
L(ift)
L(ift)
L(ift)
C(ase)
C(ase)
C(ase)
10
0n
100
n
1
00n
1
2
3
1
2
3
1
2
3
XLR female
XLR female
XLR female
Ground Lift Jumper:
Ground Lift Jumper:
Ground Lift Jumper:
GND
Earth / PE to Case
Lift
100
n
10k
Transformer
230 / 115 V AC
ANALOG UNITS POWER SUPPLY
+ U
- U
(others)
E
AC
IN
GENERAL GROUND-LIFT JUMPER
AC IN
LEFT INPUT
RIGHT INPUT
COMMAND INPUT (only G97)
VOLUME
BALANCE
POWER AMP
TIP
LEFT
RING
RIGHT
SLEEVE
GROUND
ENCLOSURE
