Power Amplifiers

Jones Audio PA-M300 Series 2 Monoblock Power Amplifier

ARTICLE INDEX

Design

In a recent phone interview with Jason Jones, I learned that his father Sam, who considers himself a lifelong audiophile, was building Heathkit amplifiers at a young age. An autodidact who started a computer software company 28 years ago, he shifted to part-time consulting seven years ago, and let others in the family run the computer business. This liberated Sam to befin working full-time on developing the amplifiers of his dreams.

Jones Audio began showing their Series 1 amps at audio shows as early as 2008. At that point, they were more interested in receiving feedback, doing much more listening, and perfecting the design. The company began to promote the amps seriously at CES 2011. A fledgling distribution network now exists in Canada, Hong Kong, and the Northeast.

One distinctive feature of the PA-M300 Series 2 monoblock is that it uses lateral MOFSET output devices. "What's great about these is that they're much faster than the bi-polar transistors you usually find," Jones explained. "That creates a much cleaner and more natural sounding high end. We encountered tube lovers at the Rocky Mountain Audio Fest who expected to hate the sound of solid-state, and couldn't believe that they liked it. This is because of these output devices.

"The MOFSETs can also take a higher range of bias and a higher total amount of bias. This helps get rid of crossover distortion, which looks like a notch in the waveform. If you increase the bias using bipolar transistors, you can create a notch in the other direction. The MOSFETS, on the other hand, can create much more bias without creating artifacts. This allows us to have a high bias amplifier that runs Class A up to 38 watts, then switches to A/B. With most music except the peak transients, the amp plays in Class A."

The Jones Audio monoblock also features a fully complementary input and voltage stage. The company claims this dual-differential design helps to cancel out some noise from the power supply, and some artifacts from differences in part tolerances. It also produces symmetrical clipping, which makes the amp operate and sound more like a tube amplifier because the positive and negative clipped waveforms look the same.

Jason stresses that the company pays particular attention to detail. (What company is going to tell you that they don't?) I wasn't sent a picture of the amp's inside, but it contains a 38 lb., ultra low-noise torroidal transformer as well as extensive heat-sinking. That's one pound for each watt of pure Class A sound. The amp's resistors, capacitors, and other parts are chosen, not according to price, but rather because they work together synergistically and sound the best (at least to the company's ears).

PA-M300 REVIEW
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