THX is usually associated with certifying the performance of commercial cinemas and consumer audio and video products. But the company is also deeply involved in developing new technologies and licensing them to manufacturers. Case in point: the THX AAA amplifier. This ultra-quiet amp design was first implemented a couple of years ago by Benchmark in the AHB2. At CanJam SoCal 2017, THX demonstrated the second generation of its AAA technology, which is specifically designed for headphone amps, claiming it to be the world’s lowest-distortion amplifier.
Actually, there are six new THX AAA modules, one of which—the AAA-888, a dual-mono design—lays claim to the title of world’s lowest-distortion amplifier. The THD (total harmonic distortion) at 32 and 300 ohms is specified to be -150 dB, while the SNR (signal-to-noise ratio) is spec’d at 134 dBA, which is impressive indeed. The other modules are stereo with a similarly low THD and high SNR, though not quite as much as the AAA-888. The AAA-888 and 788 are intended for desktop amps or DAC/amp units, while the other four are intended for battery-powered mobile devices.
As this graph indicates, the THX AAA amplifier modules exhibit much lower THD than competing amp modules at different amounts of quiescent power consumption. (Source: THX)
The THX AAA amplifier design uses a bipolar class-AB output stage with feed-forward error correction to cancel zero-crossing errors. According to THX, this allows the amp to exceed the performance of class-A designs without their low efficiency, poor damping, and high power consumption. It also allows long battery life by reducing bias currents by a factor of 10 to 100 without increasing distortion.
I listened to two demos of THX AAA amps. The first was the AAA-888 in a prototype setup (seen in the photo at the top of this article) being fed from a Benchmark DAC3 digital-to-analog converter; the source was a laptop running Tidal HiFi (uncompressed 16-bit/44.1 kHz), and the headphone was the Sennheiser HD 800 S. I selected Steely Dan’s “Hey Nineteen,” which sounded wonderful—very clean with excellent tonal balance throughout the audible spectrum. I could hear deep into the mix, with each instrument and voice clearly delineated.
Next, I checked out the AAA-0, which includes its own power supply and exhibits the lowest power consumption of all six modules. In fact, the battery life is spec’d to be around 100 hours. In this case, the source was JRiver Media Center running on a laptop and feeding another Benchmark DAC3 L, and the headphone was the Oppo PM-3. I listened to Aaron Copland’s Fanfare for the Common Man, which was stored at 24-bit/48 kHz resolution and streamed at 4.2 Mbps. The instrumentation is full brass ensemble (trumpets, French horns, trombones, tuba) with tympani, bass drum, and gong, and it sounded quite clean and powerful on this rig.
Like the AAA-888, the AAA-0 was demonstrated in a prototype form. The multimeter was set to measure milliamps being drawn by the amp in real time.
Of course, no one can hear such low THD and high SNR in the middle of a show floor, even when no speakers are blaring. But I can’t deny that both systems sounded mighty good. According to THX, the first set of products based on AAA technology should become available in the fourth quarter of 2017.
Check out this video about THX AAA amplifier technology: