AUSTIN, Texas — It seemed inevitable that Apple would respond to the many iPod boom box offerings from third parties, and in February it did just that, launching the Apple HiFi as a plug-and-play speaker system for the popular iPod family.
The HiFi is one of the more highly engineered solutions for turning the iPod from a personal headphone stereo into a room-filling sound solution. With many generations of iPods already on the market, Apple supplied the HiFi with an array of adapters to cover physical interfaces with the first iPods through the latest Nano and Video platforms.
The HiFi adapts Apple's usual white, stark casing into a boom box format. Its removable front grill reveals two wide-response speakers in a closed chamber and a single open-frame woofer that uses supplemental vents to the front with a pair of acoustic ports. A copious set of foam blocks and careful foam wrapping of all cabling presumably guard against possible vibration and buzzing from lower-frequency sound. A rear battery compartment accepts six D batteries for portable operation, though the internal ac-fed power supply is surely the preferred method to feed juice in stationary settings.
Analog output from the iPod comes in from the docking connector atop the HiFi. The set of line-in jacks means you can make use of the HiFi with other external audio sources too. Additionally, the 3.5-mm line-in connector accepts digital Mini-Toslink optical input, bringing total input options to two forms of analog and one digital.
Far from simply amplifying iPod output to levels suitable for high-power speaker drive, the HiFi contains a surprisingly complex audio-processing food chain, most of which is based on Texas Instruments semiconductor content. A pair of TI/Burr-Brown INA2134 stereo differential line receivers buffer analog input from the iPod source connector and analog inputs respectively, and send their outputs to a pair of TI/Burr-Brown PCM1802 24-bit stereo A/D converters to bring analog source input into the digital realm. A Cirrus Logic CS8420 sample-rate converter seemingly is used to harmonize the data rate of optical digital audio input to the standard used internal to the HiFi conversion and processing circuitry.
With all input sources now made available in a common serial digital format, the TI TAS3103 sound processor takes over. It's able to switch between the multiple serial inputs, where it can then perform a host of audio signal-processing chores. User adjustment to the HiFi audio is limited to normal, treble boost or bass boost--with some but not all iPods--though the device certainly supports a theoretically richer set of tone controls. The TAS3103's other function seems to be isolation of the audio signal needed for the woofer.
While the inputs to the HiFi are strictly left and right audio channels, the center bass channel must be extracted, a task seemingly performed by the TI audio DSP.
