Integrated Digital Crossover and Limiter
Most amplifiers in this market category provide limited facilities, if any, for input signal filtering and driver protection. (Typical offerings are simple analog high-pass filters and a limiter, usually selected via rear-panel DIP switches.) In contrast, the new XLS Series utilizes high-resolution digital signal processing to implement a flexible PureBand™ Crossover System and proprietary PeakX™ driver protection limiting.
Using the easy-to-read front panel LCD display and large function buttons, users can select crossover points from 50 Hz to 3 kHz on 1/12 octave centers, allowing precise matching of specified crossover points on most bi-amplified loudspeakers. Filters are fourth-order Linkwitz-Riley, with steep slopes for seamless transition between high and low drivers. Alternatively, the digital filters may be set to optimize both amplifier channels for driving either high- or low-frequency loads, or for driving full-range systems.
The PeakX limiters utilize highly effective yet sonically transparent algorithms derived from the OmniDrive HD loudspeaker drive processing in Crown’s flagship I-Tech HD Series. By precisely matching response to the output characteristics of each amplifier, PeakX enables significantly higher output levels than are possible with conventional analog limiting, yet with assured driver protection. The front panel soft-touch buttons also select limiter on/off (per channel) as well as bridge-mode on/off. There are no rear-panel DIP switches.
Advanced Switched-mode Power Supply
A highly efficient switching power supply is optimized for maximum power transfer from the AC line through the Class D output stage to the loudspeakers. Compared to older, 60Hz transformer-based power supplies, a side benefit is substantial weight reduction: all models weigh less than 12 pounds, but with no compromise of Crown’s traditionally robust build quality.
Proprietary Class D Output Stage with Integrated DriveCore™ Technology
As a type, Class D amplifiers are notable for extraordinarily high efficiency, approaching 90%. In addition, inherently low output impedance makes Class D well suited to driving difficult reactive loads such as subwoofers. However, a number of complexities make it difficult to design – and to manufacture at modest cost – real-world Class D amplifiers with sonic performance comparable to the best Class AB designs. In addition, as a type, Class D output stages are highly dependent on stable internal voltage rails, and can suffer impaired performance on marginal or unstable AC line supplies.
To overcome these obstacles, Crown engineers designed DriveCore™ - a proprietary hybrid analog-digital integrated circuit (IC) that drives the “front end” of the Class D output stage. Placed in the signal chain between the DSP module and the main power output devices, and driven fully balanced from the D-to-A converter stage, DriveCore incorporates highly refined feedback circuits and a single synchronous clock. (The DSP and switch-mode power supply clocks are both synchronized to the PWM master clock for optimum overall system stability.) Crown’s proprietary circuit-modeling techniques were employed to optimize the relationship between the new modulator chip and the power output stage. Here, Crown engineers applied the latest in power FET semiconductor technology, along with an advanced differential drive circuit topology, to offer the efficiency of Class D but with the lower distortion and residual noise typical of Class AB designs.
Other notable technology features and benefits of DriveCore Technology:
• Patented feedback and PWM modulation circuits enable fast recovery on peak transients, accurate reproduction of low-level detail, and precise tracking of low frequencies at high power levels for maximum subwoofer output.
• Integrated thermal management and protection systems ensure maximum power is delivered to the load with minimum stress on output devices.
• Advanced power supply design coupled with a wide-tolerance PWM clock maintains full performance even with sagging or “dirty” AC line conditions. The new proprietary modulator chip can handle large (up to 3:1) variations in power supply noise or sag without adversely affecting audio quality. Consequently, compared to other Class D amplifiers in this market category, performance is far less likely to be compromised by fluctuating generator power or by AC circuits sagging from marginal overloading by lighting rigs, backline gear, etc. (Prior to this development, the only way to maintain consistent performance was use of more complex – and costlier – regulated power supplies.)
Designed and Tested for Reliability
The new XLS Series of amplifiers were subjected to the same rigorous design analysis and prototype testing procedures as all Crown amplifiers, regardless of application or price point. Finite element analysis (FEA) tools simulated design behavior to optimize mechanical and thermal systems for cooler, more reliable operation in warm and high-humidity environments. All XLS Series amplifiers must pass Crown’s uniformly rigorous quality control procedures before shipping.
“The Green Edge”
XLS Series amplifiers conform to the goals of the Harman Professional Group’s “Green Edge” environmental initiative. New, high-technology circuit components not only use fewer resources in manufacturing, but also contribute to significant weight reductions that result in less energy consumption for initial shipping and end-user transportation. At the same time, extremely high operating efficiency translates into less AC line current used for each watt of output. The result is a significantly reduced “carbon footprint.”