Klippel and Nuvoton Unveil Smart Amplifier Solution with Integrated KCS Speaker Control Algorithm

August 21 2020, 00:50
Klippel announced an exciting cooperation with Nuvoton Technology, a leading provider of consumer-electronics and computer ICs from Taiwan, to release a new type of smart amplifier with integrated Klippel Controlled Sound (KCS) technology that compensates for nonlinear speaker responses. As a result of the project, Nuvoton developed the highly efficient mono Class D audio amplifier devices, NAU83G10 and NAU83G20. Both devices using Klippel's KCS adaptive nonlinear control system are now available.

Both the Nuvoton NAU83G10 and NAU83G20 devices use a low latency Tensilica HiFi Audio DSP, a high quality 24-bit audio ADCs for current and voltage sense, and a battery tracking and brownout prevention ALC, all integrated on-chip and optimized for Klippel Controlled Sound (KCS) technology. The integrated solution allows manufacturers to cope with the undesired effects of signal distortion, heat, and external influences that limit the maximum level and the quality of the reproduced sound.

The development efforts between Klippel and Nuvoton started in 2017, aiming to offer an integrated, versatile solution for the industry to fully explore the potential of the adaptive and nonlinear speaker model implemented in the KCS algorithm, to improve speaker performance and sound quality. The result is now available in two ultra-low-noise and yet powerful mono boost Class D amp devices.

The nonlinear speaker model describes speaker states such as voice coil excursion and velocity not only at low levels (small signal domain), but also in the large signal domain where the voice coil excursion is high. This allows the mechanical protection system to work very precisely over the full operating range, which is not possible with linear models. In addition, a nonlinear model can identify and actively shift the voice coil to its optimum position using a small DC voltage. This is achieved by exploiting nonlinear distortion found in the current signal, which is caused by nonlinear transducer parameters. 

These features allow the transducer to operate over a wider working range without damaging the speaker and improve the sound quality and acoustic echo cancellation (AEC) barge-in performance by reducing linear and nonlinear speaker distortion. Furthermore, the possibility of describing the speaker’s behavior in the nonlinear range of operation allows the use of transducers with more nonlinear motor topologies to focus on maximizing efficiency (Green Speaker Design).

The adaptive identification of the speaker’s resonant frequency, damping and other time-variant parameters allows KCS to compensate time-variant behavior and hence ensures that the performance stays constant over the product’s lifetime. By doing an automatic system alignment, KCS eases system tuning as the user only has to specify a target response (such as 6th order high-pass filter at a certain cut-off frequency) and KCS automatically calculates a filter to achieve this target.

The adaptive, nonlinear control system cancels the DC displacement, harmonic and intermodulation distortion generated by speaker nonlinearities (THD, IMD). Furthermore, the KCS operates the voice coil at the optimum rest position without mechanical sensor and compensates for speaker parameter variation due to aging and climate changes.
Klippel Control Sound (KCS) flow chart.

Other KCS integrated software features include predictive speaker protection against thermal / mechanical overload, automatic speaker equalization to a desired bass response, and on-line speaker diagnostics to improve product reliability. 

The new hardware and software capabilities in the NAU83G10 and NAU83G20 allow to safely operate smaller speakers at the physical limits to generate more acoustical output at higher sound quality while providing reliable protection against thermal and mechanical overload compared to conventional linear algorithms.
Nuvoton NAU83G10 block diagram.

Both the NAU83G10 and the NAU83G20 devices are mono Class D amplifiers with IV sense ADCs. A powerful Cadence Tensilica HiFi Audio DSP core is integrated inside to run the KCS algorithm efficiently, and both devices can support I2C control and I2S/PCM/TDM audio interfaces. The NAU83G10 device can deliver up to 8 W output power into 4 Ohm load and 6.5 W for an 8 Ohm load using a highly efficiency Class G boost converter. The NAU83G20 device can deliver up to 20 W for a 4 Ohm load and 1 W for an 8 Ohm load using an external battery supply around 12.6 V.

“We are very excited to be working with Klippel on creating this new breed of smart amp devices, which can deliver maximum output at unparalleled sound quality from smaller speakers, offer a precise speaker protection, provide a real time speaker diagnostic data, simplify the speaker tuning process, and increase the barge-in AEC performance compared to conventional linear model base smart amplifiers,” says Aditya Raina, president of audio product business group at Nuvoton Technology Corporation America. 

An evaluation system for the NAU83G10 and the NAU83G20 smart amp devices (pictured above) is now available, including all the necessary hardware and software to demonstrate the performance of these novel amplifiers together with KCS. The evaluation platform ships with reference speakers, initial KCS data sets and equalizer settings so that manufacturers can immediately evaluate the system’s performance. Users of the evaluation system can get a free temporary license for the Klippel QC measurement system for performing objective tests on request.

Developers will be able to connect and tune their own designs with this evaluation system for their target application. The initial identification of KCS speaker parameters is done almost automatically using the Klippel Analyzer 3 measurement system. The identification of a new speaker only takes a few minutes and the maximum working range of the device under test is identified automatically, providing comprehensive information about the suitability and potential quality of a speaker system.

NAU83G10 and NAU83G20 engineering samples and evaluation systems are available now through all Nuvoton sales channels. 
www.nuvoton.com | www.klippel.de
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