Pre/Power Amplifiers

Colorado-based PS Audio is known for a number of things: its products are handmade in its own US facilities and, as of last year, it only sells direct to its US customers. Here in the UK, PS Audio's equipment is sold more conventionally, through distributor Signature Audio Systems, which premiered the company's Stellar Phono Amplifier at the Hi-Fi Show Live at Ascot in October last year. That product, along with the Power Plant 3 AC regenerator [HFN Jan '20], is part of the new entry-level range from the company.

This review features the £1550 Gain Cell DAC (which is actually also a preamplifier), and a pair of M700 monoblock power amps, claiming a healthy 350W/8ohm, and double that into 4ohm, and selling for £2700 a brace. If you don't mind trading some of that output for compactness, there's also a stereo power amp in the range, the S300, selling for £1550, and if you want even more power you don't have long to wait: in March the company is planning to launch a Stellar M1200 monoblock, complete with a valve input stage and a 4ohm power output of – you guessed it – 1200W.

Everything To Gain
However, it's not as if the monoblocks, or indeed the DAC/preamp, are exactly space-hungry. Each unit is a fairly standard 43.2cm wide, but a slender 7.6cm tall and, despite solid, high-quality casework, they won't exactly break your back lifting them, as you might suspect if you've nipped ahead and stolen a look at the 'lid off' shots accompanying this review. There's quite a lot of fresh air in there, not least due to the compact nature of the technology used in both preamplifier/DAC and power amplifiers.

So what exactly is a 'Gain Cell DAC' when it's at home, especially when it's also a preamp? Well, PS Audio describes it as the 'Gain Cell Preamplifier', but it says 'Gain Cell DAC' on the front, so it'll come as no surprise that you can use it as just a DAC should you wish. There's a fixed output 'DAC mode' buried in the menu system, corresponding to a setting of '76' on the variable level accessed via the single front-panel knob.

Using this setting, it was possible to assess the quality of the digital-to-analogue conversion, if not alone, then at least with minimal effect from the rest of the design. The DAC chip is a familiar ESS Sabre type, which seems to be almost ubiquitous these days, partnered with passive analogue filtering and a Class A output stage.

All Analogue
The chip is fed from a choice of inputs – two coaxial and one optical, plus asynchronous USB, all using circuitry based on the company's DirectStream DAC [HFN May '18] and an I2S connection on an HDMI socket, which is suitable for use with sources such as PS Audio's DirectStream Transport.

Incoming data is handled in its native form, depending on the input used, and three digital filters are available, accessible from the front panel or the tiny remote control handset supplied, with the manufacturer saying very sensibly that 'No filter choice is wrong or right. Instead, each filter can be selected and auditioned by the user to more perfectly match their chosen [system], as well as personal tastes and biases'.

As well as its array of digital inputs, the Gain Cell DAC also has three sets of analogue ins, with three sets of RCAs and a single pair of XLRs. These feed straight into the preamplifier, with none of the 'A-to-D-to-A' nonsense seen in some digital-equipped preamplifiers. This is an all-analogue design, with the addition of a DAC stage. Or possibly a DAC combined with an analogue preamp and output control. Editor PM discusses the Gain Cell architecture in his interview boxout with PS Audio's guiding light Paul McGowan, but it's worth remembering that the preamp also offers a Class A headphone stage to feed the socket on its front panel.

Amp Technology
Within the M700 power amplifier, potted in a blue case like the preamp's Gain Cells, can be found PS Audio's 'Analog Cell' input stage, a 'zero feedback, balanced, Class A, MOSFET input stage [that] closely mirrors the sonic characteristics of a vacuum tube'. This feeds a Class D power amplifier module based on B&O's tried-and-tested ICEpower technology. Originally a collaborative project between Denmark's Technical University and B&O, the ICEpower brand has since been spun off as an independent entity.

The company's technology, though now regarded by some as being rather long in the tooth, is still used widely where compact, high-efficiency amplification solutions are required, from musical instrument applications to powered loudspeakers, products such as the M700 and in the automotive sphere – although of course other Class D amplification solutions are both available and, arguably, more fashionable.

That's Entertainment
Those who cut to the chase and start reading any review from the lab report backwards will know that PM has reservations about the level of noise and jitter measured from the Gain Cell DAC. I only got to see the lab work quite late in the review process, by which stage I'd spent considerable time with this PS Audio combo, and enjoyed several long listening sessions, both with analogue inputs and with the Gain Cell DAC/Preamp fed via USB from one of my 'audio computers'.