Exogal Comet DAC and Ion stereo power amplifier

Solid-state power amplifiers,
Digital-to-analog converters
Exogal Comet,
Exogal Ion
Exogal Comet DAC and Ion stereo power amplifier

It’s refreshing to come across a deeply engineered and well-made product that doesn’t arrive with swathes of sales guff to seduce prospective buyers. Exogal is that rare thing; an audio company that is more interested in the product than the spiel. This is probably not a great approach from a commercial perspective but makes a seasoned audio enthusiast all the more interested. Exogal was set up by industry veterans Larry Jacoby, Jeff Haagenstaad, and Jim Kinne. Jim was a digital audio pioneer and, with Larry, was a founder of Wadia – a former giant of the digital audio scene and one of the first companies to make a CD player that sounded musically compelling. Jim produced the Wadia 27 decoding computer (DAC) and matching 270 transport as well as the rare 790 Power DAC, and if anything he did in the past has influenced his work with Exogal it’s that digital amplifier. Exogal launched five years ago with the Comet DAC/preamplifier; a beautifully finished compact piece of electronics with a small and subtle display. At the time, the company announced the matching Ion power amplifier, but it took a further 18 months of “frying prototypes, speakers, and resistive loads” to turn it into a stable and consistent power DAC. 

Having finally managed to develop the Ion, a design that had “been simmering in Jim’s head for 25 years” the company is naturally not keen to divulge it’s secrets. They will say that it’s not a Class D design and that it’s not based on PWM (pulse width modulation) as is the case with NAD’s digital amplifiers. Jeff Haagenstad explained that, “Both of them [Comet and Ion] use multi-core FPGAs to implement custom math processors that take the quantized digital data and take their best shot at recreating the original analogue waveform using complex math algorithms.” Which sounds a little like what Chord Electronics does in the DACs that Rob Watts designs, except here the technology is being used to control power output. It is also used to adjust volume; when Comet and Ion are combined, output level and digital to analogue conversion are performed in the Ion, hence the power DAC appellation. Volume is controlled with DSP in the Ion; it processes signals in the amplitude domain and calculates how much power is required to achieve the desired volume. Conversion to analogue occurs just before the output (at full power), which itself highly unconventional.

The Ion has been created specifically for use with the Comet DAC; its only input is an HDMI socket for the Exonet interface for which there are in- and outputs on the Comet. There are more Exogal components in the pipeline, including a streamer that will share this intelligent connection system. The Ion’s specified power is 100 Watts into eight Ohms with peak power quoted as 150 Watts which, given the size and unventilated nature of the case, suggests very high efficiency. 

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