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Speaker drivers flaunt zero audible hiss

Posted: 24 Sep 2013     Print Version  Bookmark and Share

Keywords:Ams  active noise cancellation  stereo headset  AS3435  AS3415 

Ams AG has rolled out a couple of speaker drivers that the firm said can be used to develop noise cancellation stereo headsets with zero audible hiss. According to the company, the AS3435 and AS3415 ANC are the industry's first active noise cancellation (ANC) ICs to feature integrated bypass switches, offering headset manufacturers the freedom to create sleeker and cheaper industrial designs.

The AS3435, for feedback systems, and AS3415, for feed-forward systems, are the latest additions to Ams' portfolio of analogue ANC ICs. Incorporating ultra-low noise amplifiers with an 900nV input referred noise floor, the devices are the first ANC speaker drivers to produce no audible high-frequency hiss when paired with low-noise microphones, indicated the firm.

This means that manufacturers of audiophile products can replace existing ANC solutions with the AS3435 and AS3415 to provide users with an improved listening experience, benefiting from the devices' outstanding audio characteristics including 35mW stereo output power with THD+N of 0.1 per cent into a 32Ω load and a typical signal-to-noise ratio of >110dB.

The ANC ICs also provide for improvements to the mechanical design of a headset's housing. Conventional ANC headsets require a mechanical switch, to activate a bypass mode. When the headset's battery is completely discharged, the user must bypass the noise cancellation function in order to continue listening to music via the Line In channel. The need to accommodate this switch limits the design options for the headset's housing and circuit board.

The AS3435 and AS3415, however, feature integrated bypass switches, so that the music signal coming from the 3.5mm audio jack may be routed through the ANC chipset without any power source connected to the device. By eliminating the external switch, this feature helps to reduce BOM cost and the size of the PCB, as well as removing the need for designers to accommodate a mechanical switch on the headset's housing.

At the same time, the devices' analogue implementation of noise cancellation provides for power consumption often two or three times lower than equivalent digital solutions. Featuring typical power consumption of 10mW at 1.5V in noise cancellation mode, either device can support operation for more than 100 hours from a single AAA battery.

Ams has supported the introduction of the AS3435 and AS3415 ANC ICs with the release of an improved design tool, enabling the quicker and easier development of the filter networks that match the operation of noise cancellation to the sonic characteristics of the headset design, added the firm.

The straightforward graphical interface of the Windows-based Ams tool can display the entire signal chain across the user's screen, and provides a SPICE module for simulating the operation of filter architectures.

In the AS3435 and AS3415, Ams has also added a bass boost equalisation capability, eliminating the need for a discrete signal processing IC to perform equalisation functions.

The AS3415 and AS3435 ANC speaker driver ICs are available for sampling. Both the AS3435 feedback ANC IC and the AS3415 feed-forward ANC IC are supplied in 1,000-unit quantities. The AS3435 is in a QFN36 package, and the AS3415 in a QFN32 package, both 5x5mm.

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