Advanced Features And Options; Protection Systems; Odep; Standby Mode - Crown Macro-Tech 2402 Operation Manual

5 Advanced Features
and Options
page 14

5.1 Protection Systems

Macro-Tech amplifiers provide extensive pro-
tection and diagnostics capabilities. Protection
systems include ODEP, "standby" mode, fuses
(or breakers), and special thermal protection for
the unit's transformers.

5.1.1 ODEP

Crown invented ODEP to solve two long-stand-
ing problems in amplifier design: to prevent
amplifier shutdown during demanding opera-
tion and to increase the efficiency of the output
circuitry.
To do this, Crown established a rigorous pro-
gram to measure the safe operating area (SOA)
of each output transistor before installing it in
an amplifier. Next, Crown designed intelligent
circuitry to simulate the instantaneous operat-
ing conditions of those output transistors. Its
name describes what it does: Output Device
Emulation Protection or ODEP. In addition to
simulating the operating conditions of the out-
put transistors, it also compares their operation
to their known SOA. If it sees that more power
is about to be asked of them than they are capa-
ble of delivering under the present conditions,
ODEP immediately limits the drive level until it
falls within the SOA. Limiting is proportional
and kept to an absolute minimum—only what
is required to prevent output transistor damage.
This level of protection enables Crown to
increase output efficiency to never-before-
achieved levels while greatly increasing ampli-
fier reliability.
The on-board intelligence is monitored in two
ways. First, the front panel ODEP indicators
show whether the amplifier is functioning cor-
rectly or if ODEP is limiting the drive level. Sec-
ond, ODEP data is fed to the back panel PIP
connector so advanced PIP modules like the
IQ-PIP-USP3 can use it to monitor and control
the amplifier.
With ODEP, the show keeps going because you
get the maximum power with the maximum
protection.

5.1.2 Standby Mode

An important part of a Macro-Tech amplifier's
protection systems is standby mode. Standby
protects the amplifier during potentially cata-
strophic conditions. It temporarily removes
bias in all four output stages, protecting the
amplifier and its loads. This advanced protec-
tion implementation, called "Quad-Mute," is
new to the Macro-Tech series amplifiers.
Standby mode can be identified using the indi-
cator table in Section 6, Troubleshooting.
Standby mode can be activated in several situa-
tions. First, if dangerous subsonic frequencies
or direct current (DC) is detected in the ampli-
fier's output, the unit will activate its DC/low-
frequency protection circuitry and put the
affected channels in standby. This protects the
loads and prevent oscillations. The unit
resumes normal operation as soon as the
amplifier no longer detects dangerous low fre-
quency or DC output. Although it is extremely
unlikely that you will ever activate the ampli-
fier's DC/low-frequency protection system,
improper source materials such as subsonic
square waves or input overloads that result in
excessively clipped input signals can activate
this system.
The amplifier's fault protection system will put
an amplifier channel in standby mode in rare
situations where heavy common-mode current
is detected in the channel's output. The ampli-
fier should never output heavy common-mode
current unless its circuitry is damaged in some
way, and putting a channel in standby mode
helps to prevent further damage.
The amplifier's transformer thermal protection
circuitry is activated in very unusual circum-
stances where the unit's transformer tempera-
ture rises to unsafe levels. Under these
abnormal conditions, the amplifier will put the
channel of the affected transformer in standby
mode. The amplifier will return to normal oper-
ation after the transformer cools to a safe tem-
perature. (For more information on transformer
thermal protection, refer to section 5.1.3.)
MA 2402 Power Amplifier
An IQ-PIP module may also temporarily place
the amplifier in standby mode, typically for
power conservation. The standby mode status
can be triggered manually. The auto standby
can be triggered via the control software, in
which case the standby status will be automati-
cally cancelled when the defined level of input
signal is detected. If the unit has been placed
into a standby state, not auto-standby, this sta-
tus must be manually cleared using either
IQwic or System Architect control software.
5.1.3 Transformer Thermal Protec-
tion
The Macro-Tech 2402 has transformer thermal
protection. It protects the power supplies from
damage under the rare conditions of trans-
former temperatures rising too high. A thermal
switch embedded in each transformer removes
power to the channel if there is excessive heat.
The switch automatically resets when the trans-
former cools to a safe temperature.
It is extremely unlikely that you will ever see a
Macro-Tech 2402 activate transformer thermal
protection as long as it is operated within rated
conditions (see Section 8, Specifications). One
reason is that ODEP keeps the amplifier work-
ing under very severe conditions. Even so,
higher than rated output levels, excessively low
impedance loads and unreasonably high input
signals can generate more heat in the trans-
former than in the output devices. These condi-
tions can overheat the transformer and activate
its protection system.
The Macro-Tech 2402 is designed to keep
working under conditions where other amplifi-
ers would fail. But even when the limits of the
amplifier are exceeded, it will still protect
itself–and your investment–from damage.
Operation Manual