Crown Audio 800CSL service manual Theory, Overview, Features, Front END Operation

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Power Base-2 & 800CSL Amplifier Service Manual

Theory

OVERVIEW

It should be noted from the outset that the PB-1 and 460CSL amplifiers are electrically and mechanically identical products. The only differences, from a ser- vice perspective, are cosmetic. For the purposes of servicing the products, it should also be known that the CSL version has been on the market since 1992. Since the PB amplifiers have been in production since the mid-1980’s there are a number of electrical and mechanical parts associated with the older PB models only. It is also important to realize that over time Crown has introduced numerous improvements to PB/CSL amplifiers. Though often changes are minor, and are made for a variety of reasons, a few changes have had a significant impact on the operation of the circuitry. This manual is up to date as of the time of writing. For additional information regarding these amplifiers, re- fer 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 products Crown) the theory of operation remains simplified.

FEATURES

Power Base/CSL amplifiers utilize numerous Crown innovations including grounded bridge and ODEP technologies. Cooling techniques make use of the what is essentially air conditioner technology. Air flows bottom 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 manufactur- ers. Output 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 Power Base/CSL Series’ in-

clude a single core transformer (one primary with two independent ungrounded secondaries), 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 rear mounted. The only indicator provided tells the operator that the low voltage supply is energized. In general, the packaging of this model is designed for maximum watt/price/weight/size value. It is the most basic grounded bridge amplifier series now available from Crown.

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 (early models did not have the Ground Lift feature) 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)

Note: Older models only had two front end stages. The functions of this stage were combined, primarily, with those of the third.

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-

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Contents Power BASE-2& 800CSL Avis Table of Contents Scope WarrantyIntroduction Parts Specifications PowerPerformance MechanicalVoltage Conversion BLUFeatures TheoryOverview Front END OperationError Amp Voltage TranslatorsGrounded Bridge Topology High Side HSOutput Device Emulation Protection Odep Low Side LSPositive Checkout Procedures Test 2 Output Bias AdjustmentTest 3 Odep Voltage Adjustment Standard Initial ConditionsTest 4 AC Power Draw Test 5 Common Mode RejectionTest 7 Phase Response Test 12 Output PowerTest 16 Signal to Noise Ratio Test 14 Odep LimitingTest 15 LF Protection Test 17 Turn on TransientsPost Testing Mechanical Non-Module Parts Chassis Front Assembly Output Assembly ONE PER ChannelBack Panel Assembly Main Chassis Assembly Module Information Module HistoryOutput Modules Main ModulesQ42647-0 Output Module Parts List P10137-1 Board Q42717-1 Output Module Parts List P10233-8 Board Q42717-1 Output Module MT/MA #2 for PB-2Q42871-6 Output Module Parts List P10305-4 Board Q42871-6 Output Module MT/MA TO-3P Driver for PB-2/ 800CSLQ42966-4 Output Module Parts List P10305-4 Board Q42966-4 Output Module TO-3P Driver #2 for PB-2/ 800CSLQ43015-9 Output Module Parts List P10341-9 Board Q43203-1 Output Module Parts List P10397-1 Board Q42665-2 Main Module Original for PB-2 Q42665-2 Main Module Parts List D 6910-0 BoardNetwork Resistors Switches IC’SQ42683-5 Main Module Parts List D 6910-0 Board Q42683-5 Main Module #2 for PB-2Interconnects Zero OHMQ42818-7 Main Module Parts List D 7251-8 Board Q42818-7 Main Module 3rd Gain for PB-2/800CSLDpdt Side Header 5 PIN Q43059-7 Main Module Parts List D 7993-5 Board Jumper UPA75

800CSL specifications

Crown Audio has long been a respected name in professional audio equipment, and the 800CSL amplifiers are a testament to their unwavering commitment to quality and performance. Designed for professional sound reinforcement applications, the Crown 800CSL offers an impressive blend of power, reliability, and versatility, making it a popular choice among audio engineers and event coordinators.

At the heart of the Crown 800CSL is its robust power output. This amplifier delivers an impressive 800 watts per channel at 4 ohms, ensuring that it can drive even the most demanding speakers with ease. It features a Class D design, which not only maximizes efficiency, allowing for more power with less heat generation, but also contributes to a lightweight chassis that is easy to transport and install. This makes the 800CSL a versatile option for both permanent installations and mobile events.

One of the key technologies employed in the Crown 800CSL is its comprehensive built-in protection circuitry. This includes advanced short circuit protection, over-temperature protection, and current limiting. Such features ensure that the amplifier operates reliably in challenging conditions, reducing the risk of damage to both the amplifier and the connected speakers. The inclusion of a low-frequency filter further enhances performance, providing clean, powerful bass without distortion.

The Crown 800CSL also offers a range of connectivity options, including XLR and ΒΌ-inch inputs, making it compatible with a wide variety of audio sources. This flexibility, combined with user-friendly front panel controls, allows audio professionals to set up and adjust the system quickly and efficiently.

Additionally, the amplifier features a robust and compact design with a lightweight aluminum chassis. This not only contributes to its portability but also aids in heat dissipation, further enhancing performance during prolonged use. The included handles on the chassis make it easy to transport the unit between gigs, while its durable components ensure longevity.

In summary, the Crown Audio 800CSL stands out for its power, efficiency, and reliability. From its Class D amplification technology to its comprehensive protection features, this amplifier is designed to meet the needs of professionals in the audio industry. Whether for concerts, events, or installations, the 800CSL is poised to deliver exceptional sound quality and performance, making it a valuable addition to any audio toolkit.
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