Specifications

page 19
Studio Reference I & II Professional Studio Amplifiers
Operation Manual
4 Advanced Features
and Options
This level of protection enables Crown to increase
output efficiency to never-before-achieved levels
while greatly increasing amplifier reliability.
The on-board intelligence is monitored two ways.
First, the amplifier’s ODEP indicators show whether
the unit is functioning correctly or if ODEP is limit-
ing output. Second, ODEP data is fed to the ampli-
fier’s internal PIP connector so advanced PIP
modules like the IQ-PIP can use it to monitor and
control the amplifier.
This is how ODEP keeps the show going with maxi-
mum power and maximum protection at all times.
4.2.2 Standby Mode
An important part of a Studio Reference amplifier’s
protection systems is standby mode. Standby pro-
tects the amplifier during potentially catastrophic
conditions. It temporarily removes power from the
high-voltage supplies to protect the amplifier and its
loads. Standby mode can be identified using the
Troubleshooting chart in Chapter 6.
Standby mode is activated in five situations. First,
when you turn on the enable switch, standby mode
is activated to provide turn-on protection. This
power-up delay lets other system components settle
before any signals are amplified and it provides
some power-up “randomness” for multiple units so
the system’s start-up current demands are better
distributed over time.
The amplifier’s overvoltage protection circuitry
will put both channels into standby when excessive
AC mains voltage is detected. Studio Reference
amplifiers should not be operated with an AC mains
voltage of more than 10% over the unit’s rated volt-
age.
If dangerous subsonic frequencies or direct current
(DC) is detected in the amplifier’s output, the unit
will activate its DC/low-frequency protection
circuitry and put the affected channels in standby.
This protects the loads and prevents oscillations.
The amplifier resumes normal operation as soon as
it no longer detects dangerous low-frequency or DC
output. Although it is extremely unlikely that you
will ever activate the amplifier’s DC/low-frequency
protection system, improper source materials such
as subsonic square waves or input overloads that
result in excessively clipped signals can activate
this system.
The amplifier’s fault protection system will put an
amplifier channel into standby mode in rare situa-
tions where heavy common-mode current is
detected in the channel’s output. The amplifier
should never output heavy common-mode current
unless its circuitry is damaged in some way, and
putting the channel into standby mode helps to pre-
vent further damage.
The amplifier’s transformer thermal protection
circuitry is activated in very unusual circumstances
where the unit’s transformer temperature rises to
unsafe levels. Under these abnormal conditions, the
amplifier will put both channels into standby mode.
The amplifier will return to normal operation after
the transformer cools to a safe temperature. (For
more information on transformer thermal protection,
refer to the section that follows.)
4.2.3 Transformer Thermal Protection
All Studio Reference amplifiers have transformer
thermal protection which protects the power sup-
plies from damage under rare conditions where the
transformer temperature rises too high. A thermal
switch embedded in the transformer removes power
to the high-voltage power supplies if it detects
excessive heat. The switch automatically resets
itself as soon as the transformer cools to a safe tem-
perature.
If your amplifier is operated within rated conditions,
it is extremely unlikely that you will ever see it acti-
vate transformer thermal protection. One reason is
that ODEP keeps the amplifier working under very
severe conditions. Even so, higher than rated output
levels, excessively low-impedance loads and unrea-
sonably high input signals can generate more heat
in the transformer than in the output devices. This
can overheat the transformer and activate its protec-
tion system.
Studio Reference amplifiers are designed to keep
working under conditions where other amplifiers
would fail. But even when the limits of a Studio Ref-
erence amplifier are exceeded, it still protects
itself—and your investment—from damage.
4.2.4 Circuit Breaker
A back panel circuit breaker is provided to prevent
excessive current draw by the high-voltage power
supplies. 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
Studio Reference II configured for 100 to 120 VAC
uses a 20 amp circuit breaker, and the 220 to
240 VAC version has a 10 amp circuit breaker. With
rated loads and output levels, this breaker should
only trip in the incredibly rare instance of a cata-
strophic amplifier failure. The ODEP system keeps
the amplifier safe and operational under most other
severe conditions. The breaker can also trip in situ-
ations 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 condi-
tions, like when the amplifier is used to drive a 1
ohm load, or when an input signal is clipped
severely.
4.3 Filter Cleaning
A dust filter is provided on the amplifier’s air intake
(see Figure 3.1). If this filter becomes clogged, the
unit will not cool as efficiently as it should and high
heat sink temperatures may produce lower-than-
normal output.
Dust filters are not 100% efficient—depending on
the local environment, the internal heat sinks of the
amplifier will benefit from periodic cleaning by a
qualified technician. Internal cleaning information is
available from our Technical Support Group.