TI's New Headphone Chip
On June 10, the technology giant announced a new high-performance headphone driver with specifications that make it ideal for use with high-resolution sources such as DVD-Audio or SACD. The TPA6120A2 has astounding specifications, with dynamic range and signal-to-noise ratio that exceed 120dB. Equally astounding is the chip's slew rate (ability to respond to signal changes) of 1300V/µs. Combined with the TPA6120A2's current-feedback architecture, these specs give the chip "exceptional dynamics, detail and harmonic accuracy," according to TI marketing manager Eric Droge ("drog-ee"), in a phone conversation June 16.
The chip has a rapid-response FET input stage and the ability to deliver almost one volt of output signal to impedances less than 2k ohms, a bit of designed-in ruggedness given that headphone impedances are all over the map—a range typically from 8 ohms to 600 ohms. Evaluation listening was done with a pair of high-quality Grado 'phones with 32 ohm impedance, Droge mentioned.
The chip's incredible slew rate and current feedback architecture are said to prevent odd-order distortion (what audiophiles sometimes call "transistor sound"). Its gain-independent frequency response maintains the full frequency bandwidth of the amplifier at any gain setting, insuring sonic consistency regardless of listening level, TI claims.
Intended for inclusion in high-resolution audio devices, the TPA6120A2 should also find a home in recording and mastering studios as well as in monitoring situations in live concerts. Droge noted that TI researchers found some "roadies" often listen through headphones at levels of 80mW/600ohms, and sometimes as high as 1W. The TPA6120A2 should not only upgrade their on-the-job experience, but also prove durable enough for long term high-output use.
When asked about possible pro use incorporated into plug-in modules, Droge said TI engineers were very sensitive to signal degradation from less-than-ideal connectors. "We prefer high-quality gold-plated connectors as found on audiophile equipment," he said. Stereophile readers wouldn't argue with that.
TI marketers expect audio professionals to embrace the TPA6120A2 in droves once they get a taste of it. Droge hopes the high-fidelity market will do likewise. In a standard "PowerPAD" surface mount 20-pin small outline package (SOIC), the headphone driver is said to perform optimally with TI's OPA4134 audio operational amplifier (op amp) and PCM1792 or DSD1792 digital-to-analog converter (DAC) from the company's Burr-Brown product line. Both DACs accept 24-bit PCM and 1-bit DSD audio data formats, are said to have "improved tolerance to jitter" and are claimed capable of a 132dB dynamic range, near the limits of human hearing. The entire audio chipset maintains a dynamic range greater than 120dB. The entire chipset enables "a pure and natural sound so breathtaking the listener could mistake it for the original source," according to the announcement.
The TPA6120A2, OPA4134, PCM1792 and DSD1792 are available now from Texas Instruments and authorized distributors, with suggested resale pricing in quantities of 1000 as follows: $1.90/each for the TPA6120A2, $1.75/each for the OPA4134 and $13.65/each for the PCM1792 or DSD1792. Educated guess: finished products with the high-performance chips should appear in time for the 2005 Consumer Electronics Show, scheduled for January.