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5b. ‘HiFi/Pro’ Switches for Balanced XLR inputs
For the majority of sources, the HiFi/Pro switch (R3) is best left in the ‘HiFi’ position. However, if the source has
a pro-audio style transformer balanced output, the HiFi/Pro switch needs to be set to ‘Pro’.
A transformer balanced output uses a floating secondary from an audio transformer: unlike electronic balanced
outputs of any description, the signal is NOT referenced to ground (Pin 1). For such (rather rare) equipment, the
‘Pro’ switch is engaged to short-scircuit Pins 1 & 3, thus establishing the ground connection.
‘Pro’ switch is for
the few pre-
amplifiers that
have floating
transformer
balanced outputs
HiFi
Pro
Mode
Int
Amp
Power
Amp
L
R
M
Power
On
Off
Sync
Balanced
Input
Designed andEngineered in GreatBritain
Dual MonoAmplifierAM 77
-
+
+
_
_
90V 135V
190V
260V
～
AC IN
Speaker
Output
Speaker
Output
LR
IR Link
L
R
1
5
4
3
2
Inputs
No UserServiceableComponentsInside.
,
.
.
For servicecontact your Authorised
Dealer orDistributorAny modifications to
this equipmentwillvoid all warranties
CAUTION ATTENTION
RISK OFELECTRIC SHOCK
DONOT OPEN
RISQUEDE CHOC ELECTRIQUE
NEPAS OUVRIR
!
,
() .
.
Under normaloperationset all switches to
the default positionPleasereferto
the instructionmanualforfurtherdetails
bold
HiFi
Pro
Mode
Int
Amp
Power
Amp
-
Option
SERIAL NO.
L
R
M
M
In
Out
AM 77-
AM 77-
M
M
M