Sonoma HPEL Electrostatic Technology

The ideal loudspeaker transducer would have zero mass, respond infinitely quickly to any signal, be perfectly damped, have no distortion and be perfectly linear. Until now, the technology that best exemplifies those characteristics is electrostatic. Introduced almost 60 years ago, electrostatic headphones have remained the choice of discerning listeners who demand the highest audio quality. Now, a revolutionary new electrostatic transducer, derived from the world of ultrasonics, has been developed in the UK by Warwick Audio Technologies Ltd. (WAT). The patented High-Precision Electrostatic Laminate (HPEL) audio transducer ushers in a new paradigm in the field of electrostatic drivers, and the Sonoma M1 is the first headphone system in the world to use it.

The HPEL uses a thin (15 μm – less than the thickness of a human hair), flexible laminated film for the ‘front’ grid. Thanks to a proprietary Finite-Element Analysis software package, WAT is able to fine tune the characteristics of the ‘drum-skins’ such that they have different resonant frequencies. Each cell is acoustically independent, but driven in parallel. As a result, the sound from each cell combines in acoustic space, but the independent resonances average out, avoiding any large resonant peak in the audio band (as can happen with a single driver area). The result is a neutral, fast, natural sound with outstanding resolution.


The thin, light laminate material ensures an extended frequency response, with the panel remaining linear to over 60 kHz. The HPEL has unmatched transient performance, and its surface area has been maximized to deliver a full frequency response. As a result the Sonoma headphone system delivers High-Resolution Audio in unparalleled sound quality. Additionally, because it is produced with modern automated manufacturing techniques, the HPEL delivers unprecedented consistency and matching between transducers for a guaranteed quality listening experience. The simplicity of its design also enables exceptional durability and reliability.


Reference Dual DAC Design

The Sonoma M1 system was developed to deliver true high-resolution performance. For the critical digital-to-analog conversion stage, Sonoma turned to an established leader in the field ESS Technology. Ess is universally recognized as the world’s premier DAC chip manufacturer, and their 32-bit Reference DAC was selected. Two stereo DAC chips are used in a special mono mode to deliver an outstanding 129 dB signal-to-noise ratio (SNR).

Discrete Single-Ended Class-A Amplifier

A high-performance, single-ended, discrete FET Class-A amplifier was designed and optimized to drive the inherent capacitive load of the electrostatic transducers and provide the high voltage needed with very low distortion and wide bandwidth. The Class-A output stage is operated at a high bias level for improved linearity. High quality devices are used throughout which are designed to cope with the power levels.

FETs are often said to combine the sonic characteristics of tubes with the reliability of solid-state and the Model One uses high quality International Rectifier FETs intended for linear amplifier applications. The attention to detail continues with use of the best passive components—optimized for their specific application in the electronic design. To ensure isolation from all interference sources, the amplifier is encased in a completely shielded, machined aluminum enclosure.

CNC-Machined Aluminum Amplifier Enclosure

The Model One amplifier is a very substantial unit featuring high quality solid aluminum casework. A special 3D-wave pattern is then cut into the base and top-plate by CNC-machine to facilitate heat dissipation. To obtain the desired finish in the metal, the machined parts are then blasted under high pressure with fine glass beads before being clear anodized. Finally, all logos and labels are laser-etched into the metal, so will not fade or rub off!

A beautiful case would be of little use if it did not help to improve system performance. The entire M1 chassis is electrically conductive, and acts as an ideal EMI/RFI shield. Care was taken to ensure a low impedance ground path between every mechanical component of the chassis and the power ground plane, which extends to the custom universal power supply and earth ground. The signal ground is kept isolated from this protective shield, and all these features together contribute to the ultra-low noise floor and freedom from external interference.

High Quality Optimized Cables

As USB is the only connection which accepts all the high-resolution digital audio formats which the Sonoma M1 supports (PCM up to 32-bit/384 kHz and DSD64/DSD128) it was vital to ensure that there was no compromise in performance when using this connection. Consequently, in collaboration with Straight Wire Inc., a custom USB cable was developed which features gold-plated connectors and a silver-plated data path, it is the ideal connection between your digital music source and the Sonoma M1 system.

Custom High-Frequency Power Supply

For the M1 Sonoma designed a custom high-frequency power supply perfectly suited for electrostatics and high-resolution music. The power supply operates well above the audible band and is extremely efficient so it delivers astonishing low-noise performance with plenty of amplifier headroom. Inside the amplifier high-current power goes through multiple stages of low-noise regulation and digital and analog power are completely isolated to further reduce noise. A custom high quality braided and shielded cable with a high quality Switchcraft locking DC connector make a solid and reliable connection and complete this end-to-end system engineered to produce the best sound available on the market today.


Want more technical information? Click the logo at right to visit the Sonoma Acoustics web site.



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