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Studio Reference
IIIII
&
II
II
II
II
II
Professional Studio Amplifiers
former than in the output devices. This can overheat
the transformer and activate its protection system.
Studio Reference amplifiers are designed to keep work-
ing under conditions where other amplifiers would fail.
But even when the limits of a
Studio Reference amplifier
are exceeded, it still protects itself—and your invest-
ment—from damage.
4.3.4 Circuit Breaker
A back panel circuit breaker is provided to prevent ex-
cessive current draw by the high-voltage power sup-
plies. A
Studio Reference
I
configured for 100 to
120 VAC has a 30 amp circuit breaker, while the 220 to
240 VAC version has a 20 amp circuit breaker. A
Stu-
dio Reference
II
configured for 100 to 120 VAC uses a
20 amp circuit breaker, and the 220 to 240 VAC ver-
sion has a 10 amp circuit breaker. With rated loads and
output levels, this breaker should only trip in the incred-
ibly rare instance of a catastrophic amplifier failure. The
ODEP system keeps the amplifier safe and operational
under most other severe conditions. The breaker can
also trip in situations where extremely low-impedance
loads and high output levels result in current draw that
exceeds the breaker’s rating. Again, this should only
be possible when operating
outside rated conditions,
like when the amplifier is used to drive a 1 ohm load, or
when an input signal is clipped severely.
4.4 Controls
The front panel
enable switch
is used to turn the ampli-
fier on and off. If you ever need to make any wiring or
installation changes, don’t forget to disconnect the
power cord first. Please follow these steps when first
turning on your amplifier:
1. Turn down the level of your audio source. For
example, set your mixer’s volume to –
(off).
2. Turn down the amplifier’s level controls.
3. Turn on the enable switch. The enable indicator be-
side the switch should glow. During the four second
turn-on delay that immediately follows, the indica-
tors will flash as described in Figure 4.2. After the
delay, the
ODEP indicators should come on with full
brilliance and the
IOC and signal presence indica-
tors should function normally.
4. After the turn-on delay, turn up your source to the
maximum desired level.
5. Turn up the amplifier’s level controls until the maxi-
mum desired sound level is achieved.
6. Turn down the level of your audio source to its
normal range.
Each of the front panel
level controls
has 31 detents
for accurately repeatable settings. In Bridge-Mono and
Parallel-Mono modes, the channel 2 level control
should be turned down.
The
meter switches
are located behind the front
panel. They make it possible to switch between the dy-
namic range and signal level display modes for the
meters, or you can turn the meters off. From the factory,
the meters automatically display dynamic range
(which is computed as the ratio of peak to average out-
put power). To change these switches, you will need to
remove part of the front panel. A phillips screwdriver
will be needed, and it will help to remove the amplifier if
it is mounted in a rack. Follow these steps:
1. Make sure the amplifier is turned off and its power
cord is disconnected from the AC mains source.
2. Remove the two screws that hold each end cap in
place and remove both end caps (see Figure 3.2).
3. Remove the six screws that hold each handle in
place and remove each handle (see Figure 4.3).
4. Remove the dust filter by gently pulling it away from
the front panel.
5. Remove the two screws that secure the lower half of
the front panel and remove the lower front panel.
6. Locate the meter switches as shown in Figure 4.4.
Set the switches as desired. The left switch is used
to turn the meters on and off, and the right switch is
used to change display modes.
7. Reassemble the front panel, handles and end caps
in reverse order of disassembly.
8. Install the amplifier and reconnect power.
Fig. 4.3 Removing a Handle
AMPLIFIER TOP VIEW
(FRONT LEFT CORNER—END CAP REMOVED)
To remove the handle,
pull firmly from the side.
