Phison A2.12 stereo power amplifier

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Solid-state power amplifiers
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Phison Audio A2.12
Phison A2.12 stereo power amplifier

It’s pronounced like ‘bison’ because it’s a combination of the founder’s forenames; Philip and Sonny, and they’re Danes. But you can tell that from the understated elegance of the Phison design, of course. There are many aluminium blocks in the world of high-end power amps, but this one is that bit more precise and compact than most. It is, however, no lighter. The size makes you think the A2.120 shouldn’t be too much of a brute, but 28kg is heavy whatever size it comes in.

Phison co-founder, Sonny Andersen, started out making electronics, for himself but eventually contacted local high-end company Raidho where he helped to build what would become the Aavik power amplifier. But that was not before he got into making electronics on an OEM basis for the audio and logistics world. So it was perhaps inevitable that Sonny would start building his own amplifiers on a commercial level, and this started with the Phison PD2 balanced preamplifier, which uses discrete modules that are created in-house. This preamp can be a line stage alone or have a DAC and/or phono stage onboard, and it can be operated with either a Phison handset or an Apple TV remote, an inexpensive but attractive alternative.

The A2.120 is so-called because it has two channels of 120 Watts (8 Ohms, 220W/4 Ohms) in its matte anodised, clean lined casework. The weight is accounted for by two power transformers, but these are not used in a dual mono configuration because Sonny wanted to be able to bridge the output (delivering 300 Watts into 8 Ohms) and separate power supplies can’t produce so much power. The A2.120 is built around the same gain stage as the Phison preamp, with a current feedback module preceded by a voltage feedback stage that sets the gain. The output stage has 14 bipolar transistors per channel so as to cope with the demand when the amplifier is bridged, and the gain module incorporates both JFETs and bipolar devices.

The power supply as you may have guessed is a linear type, hence the substantial transformers. Phison experimented with switch-mode supplies, but came to the conclusion that the company could get better bass performance with a more traditional approach. Which is odd because my own experience is that the limitations of SMPS are usually more obvious in the treble, but implementation is everything with audio circuits. Here the bandwidth has been restricted with a simple low pass filter to 330kHz to avoid instability, but notionally at least, the design could be used at up to 800kHz.

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