Axiom Audio - July 20, 2012

Research and Design: Part 2

Until a few years ago, Axiom Audio made only speakers. That changed when Axiom released the A1400-series amps in 2007. That model has been discontinued, and Axiom is currently in the process of releasing the new ADA-series amplifiers, . . .

. . . which Andrew Welker designed from the ground up. ADA stands for "Axiom digital amplifier," which reflects the class-D output stage that was designed in-house. The power supply, though, is a linear design, which Welker feels offers superior performance and reliability compared to a switching supply.

There are 21 ADA models spread across three "power-supply platforms." The platforms are called 1000, 1250, and 1500, with each having seven models ranging from two to eight channels. The number of channels is reflected in the model name, and the main difference between each platform is how much power the models can produce. For example, in stereo configurations, the ADA1000-2 ($980 USD) can produce 125Wpc into 8 ohms or 250Wpc into 4 ohms, the ADA1250-2 ($1870) can produce 225Wpc into 8 ohms or 450Wpc into 4 ohms, and the ADA1500-2 ($2380) can produce 325Wpc into 8 ohms or 650Wpc into 4 ohms. As the number of channels increases in any series, the power per channel decreases due to power-supply limitations because the channels share the supply. But the ADA-1500-8, which is the highest-powered amplifier with the highest number of channels, is still claimed to deliver 188Wpc continuously -- with all eight channels driven! That's a lot of power -- particularly when you consider that there's likely never to be an instance when all channels are called on to deliver maximum power at once.

The ADA amplifiers are currently shipping, so the Axiom technicians were busy readying the circuit boards when we visited. Shown above are two circuit boards in varying stages of completion.

The ADA amplifiers are modular designs, meaning that each completed amplifier module plugs into what Welker calls the "power-supply motherboard." It's possible to expand an amplifier by plugging additional channels into the board.

The finished ADA amplifiers look impressive inside.

The ADA amplifiers are very powerful for their size and price. Andrew Welker used an Audio Precision measurement system to demonstrate that an ADA1500-series model will deliver up to 1300W into a 2-ohm load with less than 1% THD (one channel driven). Impressive!

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