Crown Audio 2400 service manual Theory, Overview, Features, Front END Operation

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Micro-Tech 2400 Amplifier Service Manual

Theory

OVERVIEW

It should be noted that over time Crown makes im- provements and changes to their products for various reasons. This manual is up to date as of the time of writing. For additional information regarding these amplifiers, refer to the applicable Technical Notes provided by Crown for this product.

This section of the manual explains the general opera- tion of a typical Crown power amplifier. Topics cov- ered include Front End, Grounded Bridge, and ODEP. Due to variations in design from vintage to vintage (and similarities with other Crown products) the theory of operation remains simplified.

FEATURES

Micro Tech amplifiers utilize numerous Crown innova- tions including grounded bridge and ODEP technolo- gies. Cooling techniques make use of the what is essentially air conditioner technology. Air flows bot- tom to top, and front to side. Air flows a short distance across a wide heatsink. This type of air flow provides significantly better cooling than the “wind tunnel” technology used by many other manufacturers. Out- put transistors are of the metal can type rather than plastic case. This allows for a significantly higher thermal margin for the given voltage and current ratings. All devices used are tested and graded to ensure maximum reliability. Another electronic tech- nique used is negative feedback. Almost all power amplifiers utilize negative feedback to control gain and provide stability, but Crown uses multiple nested feedback loops for maximum stability and greatly improved damping. Most Crown amplifiers have damp- ing in excess of 1000 in the bass frequency range. This feedback, along with our compensation and ultra-low distortion output topology, make Crown amplifiers superior.

Features specific to the Micro Tech Series’ include two seperate power transformers (one for each channel), a full time full speed fan which also serves as the low voltage transformer, slew rate limiting, and audio muting for delay or protective action. This amplifier can operate in either a Bridged or Parallel Mono mode as well as dual (stereo). A sensitivity switch allows selection of input voltage required for rated output. Level controls are mounted on the rear panel and are of the rotary type. Front panel indicators let the user know the status of the low voltage power supply (enable), and an ODEP indicator for each channel which shows the reserve energy status. In general, the

packaging of this model is designed for maximum watt/price/weight/size value with user friendly fea- tures.

For additional details refer to the specification section, or to the applicable Owner’s Manual.

FRONT END OPERATION

The front end is comprised of three stages: Balanced Gain Stage (BGS), Variable Gain Stage (VGS), and the Error Amp. Figure 1 shows a simplified diagram of a typical front end with voltage amplification stages.

Balanced Gain Stage (BGS)

Input to the amplifier is balanced. The shield may be isolated from chassis ground by an RC network to interrupt ground loops via the Ground Lift Switch. The non-inverting (hot) side of the balanced input is fed to the non-inverting input of the first op-amp stage. The inverting (negative) side of the balanced input is fed to the inverting input of the first op-amp stage. A potentiometer is provided for common mode rejection adjustment. Electrically, the BGS is at unity gain. (From an audio perspective, however, this stage actually provides +6dB gain if a fully balanced signal is placed on its input.) The BGS is a non-inverting stage. It’s output is delivered to the Variable Gain Stage.

Variable Gain Stage (VGS)

From the output of the BGS, the signal goes to the VGS where gain is determined by the position of the Sen- sitivity Switch, and level is determined by the level control. VGS is an inverting stage with the input being fed to its op-amp stage. Because gain after this stage is fixed at 26dB (factor of 20), greater amplifier sensi- tivity is achieved by controlling the ratio of feedback to input resistance. The Sensitivity Switch sets the input impedance to this stage and varies the gain such that the overall amplifier gain is 26 dB, or is adjusted appropriately for 0.775V or 1.4V input to attain rated output.

Error Amp

The inverted output from the VGS is fed to the non- inverting input of the Error Amp op-amp stage through an AC coupling capacitor and input resistor. Amplifier output is fed back via the negative feedback (NFb) loop resistor. The ratio of feedback resistor to input resistor fixes gain from the Error Amp input to the output of the amplifier at 26 dB. Diodes prevent overdriving the Error Amp. Because the Error Amp

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Contents MICRO-TECH-2400 Avis Table of Contents Scope WarrantyIntroduction Parts Information Specifications PowerVoltage Conversion Features TheoryOverview Front END OperationVoltage Amplification Grounded Bridge TopologyLast Voltage Amplifiers LVAs Voltage TranslatorsHigh Side HS Low Side LSOutput Device Emulation Protection Odep Positive Electrical Checkout Procedures Test 7 Phase Response Test 12 Output PowerTest 6 Voltage Gain Test 8 Level ControlsTest 16 Signal to Noise Ratio Post TestingTest 14 Odep Limiting Test 15 LF ProtectionParts List Non-Module Power SupplyOutput Assembly ONE PER Channel Supplimental ItemsChassis Front Assembly Output Assembly CONT. ONE PER ChannelBack Panel Assembly Main Chassis Assembly MiscellaneousModule Information Module HistoryMain Modules Fuse ModuleM46330-3 Fuse Module & Q43327-8 Display Module Parts List DiodesLeds ResistorsQ43354-2 Output Module Parts List P10429-2 Board CapacitorsInductors TransistorsQ43328-6 Main Module Parts List D8679-9 Board Q43328-6 MT-2400 Original Main Module Use Schematic JQ43328-6 Main Module Parts List Cont. D8679-9 Board Resistor NetworksSwitches Test PointsQ43328-6 Main Module Parts List Cont. D8679-9 Board Q43399-7 Main Module Parts List D8827-4 Board Q43399-7 MT-2400 Main Module Use Schematic JQ43399-7 Main Module Parts List Cont. D8827-4 Board TP1 TP2 U103A U203A Open

2400 specifications

Crown Audio is a well-respected name in the audio industry, known for its powerful and reliable amplifiers. Among its notable products is the Crown Audio 2400, a high-performance amplifier that has garnered attention for its impressive range of features and technologies.

The Crown 2400 is part of the XTi series, which is renowned for delivering exceptional sound quality and performance. A key feature of the 2400 is its innovative Class-I technology. This design allows the amplifier to remain highly efficient while producing substantial power output, making it suitable for a variety of applications, from live sound to installation settings. With a power rating of 2400 watts per channel at 4 ohms, the XTi 2400 provides ample power for driving multiple speakers, ensuring that audio can fill even the largest spaces.

Another standout characteristic of the Crown 2400 is its built-in DSP capabilities. This onboard digital signal processing allows users to tailor the audio output to their specific needs. The DSP features include adjustable crossover settings, EQ adjustments, delay settings, and limiting functions, all accessible through an intuitive LCD interface. This user-friendly design enables quick adjustments in real-time, which is critical in dynamic live performance environments.

The amplifier also boasts advanced connectivity options, including both XLR and 1/4-inch input connectors, allowing for versatile integration with various audio sources. Additionally, the inclusion of Speakon outputs provides secure and reliable connections to speakers, minimizing the risk of accidental disconnects during performance.

Thermal management is another area where the Crown 2400 excels. The amplifier is equipped with a comprehensive cooling system, which includes a variable-speed fan and extensive heat sinking. This design ensures that the amplifier operates efficiently even under heavy load, prolonging its lifespan and maintaining optimal performance.

Finally, the Crown Audio 2400 is designed with durability in mind. Its rugged construction makes it suitable for the rigors of touring and demanding live environments, reinforcing Crown's commitment to quality and reliability.

In conclusion, the Crown Audio 2400 stands out as a powerful and versatile amplifier, offering Class-I technology, robust onboard DSP, excellent connectivity options, advanced thermal management, and durable construction. These features make it an ideal choice for audio professionals seeking reliability and high performance in their sound systems.
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