Integrated Amplifiers

PS Audio’s new Stellar Strata MK2 amplifier looks – at first glance – identical to the original Stellar Strata [HFN Mar ’21], save the ‘MK2’ lettering now added to its fascia. The slender chassis, offered in silver or black and a feature of all Stellar series hardware, is retained, as is the slim text display, right-side volume rotary and headphone output of its predecessor. So from the off, it’s clear that any changes made for this second-generation design are under the hood.

This is indeed the case, although unusually for a product intended to upgrade on what’s come before, there have been subtractions as well as additions. Comparing the original and new Stellar Strata becomes indicative of how the American manufacturer’s entry-level range (excluding its budget Sprout amplifier) continues to evolve, and in a way that’s not always entirely logical. For example, this latest Stellar model hasn’t been deemed worthy of ‘Gold’ status, unlike the recent StellarGold DAC [HFN Jan ’24] and partnering StellarGold preamplifier.

Groove approved

Arguably the most significant change for this MK2 iteration is the excising of PS Audio’s network audio platform. So… gone are the Ethernet and Wi-Fi connections, and playback from streaming sources through the company’s Connect app, meaning access to the unit’s built-in DAC is via physical inputs only. This makes the Stellar Strata MK2 less of a ‘just add speakers’ amp than its predecessor, as well as numerous competing products at this £3500 asking price that put streaming at the heart of their features roster.

So why the change? Because, says PS Audio, this second-gen model now includes a phono stage, whereas the original offered no support for turntable owners. Explains PS Audio’s CEO Paul McGowan: ‘Many of our customers were unhappy they needed an external phono stage for their turntable set-ups. We originally toyed with the idea of keeping the streamer and adding in the phono stage, but economics and back panel space didn’t really work for us’.

McGowan also says that PS Audio’s AirLens streamer [HFN May ’24], launched in 2023, ‘solves the problem better than the module we used on the [Stellar Strata] MKI’. That’s as maybe, but as the AirLens sells for £1999 [see boxout], it’s likely some Stellar Strata MK2 owners will look elsewhere for their streaming needs.

Vinyl enthusiasts, on the other hand, can make use of a new phono module that supports both MM and MC cartridge types, with a fixed gain of 40dB and 57dB, and loading of 47kohm and 100ohm, respectively. Inputs are on separate RCAs, and their presence has necessitated a slight rejigging of the amp’s rear-side connectivity. As before, though, the rest of the connections are split into analogue and digital banks. Ranged to the left are USB-B, optical, coaxial (x2) and now two I²S inputs on HDMI sockets, while two sets of RCA analogue ins (one configurable to a fixed volume for using the amp in a home theatre system), and a balanced XLR input, sit to the right. Between are an RCA analogue output for an external amp or subwoofer, plus 12V triggers.

Juice boost

Like its predecessor, the Strata MK2 uses an ICEpower Class D amp module as its output stage. PS Audio rates the MK2 at 2x100W/8ohm (150W/4ohm), but PM’s independent measurements[see PM's Lab Report] reveal it is squeezing slightly more juice from the Class D stage. So, the MK2 is even more of a wolf in sheep’s clothing than the original, despite PS Audio making no claims of a power boost.

For the preamp stage, the Strata MK2 employs PS Audio’s fully balanced ‘Analog Gain Cell’ design, although the variable gain amplification of the MK1 model has been replaced by a new CMOS-based stepped attenuator here. The DAC stage has also been revamped, with an ESS ES9018K2M chip now part of a design incorporating PS Audio’s low-jitter ‘Digital Lens’ clock [see PM's Lab Report].

This amp maintains the look and feel of the wider Strata family, being reassuringly solid in construction (including the chunky speaker binding posts) and blessed with a size and weight that can make other amps appear unmanageable. Control is via a supplied remote which sits snugly in the palm and is very responsive, but has a plastic construction that doesn’t complement the rest of the hardware. This handset is good for volume adjustment, input switching (once again, these are labelled 1-9 so you’ll need to memorise what’s what) and selecting between the amp’s three digital filters. More deep-level tweaks are made through the Strata MK2’s display, with menus offering MM/MC mode selection, input renaming, max volume settings, and more.

Magic in the mix
Similar to the MK1 model, the Stellar Strata MK2 is deceptively powerful, with an authenticity to its driving ability that should make it a match for any likely partnering loudspeaker around the price point, in my case my usual B&W 705 S3 Signatures [HFN Aug ’24], and KEF’s Q11 Meta floorstanders [HFN Mar ’25]. Its sound never lacked for get-up-and-go, and its bass performance was eye-opening, to the point it’s easy to imagine you’re listening to bigger, heftier hardware. PS Audio’s integrated amp sounds lively and effervescent with up-tempo material, always ready to dig into a bassline or propel a rhythm forward.

Next to this, however, there’s also an openness and resolution to the performance that allows the listener to become engrossed by complex mixes. Playing The Police’s ‘Every Little Thing She Does Is Magic’ [Every Breath You Take: The Classics, A&M; 88.2kHz/24-bit], via the amp’s USB-B connection from a MacBook, gave a good example of its nicely balanced presentation. The crisp hi-hats that open the track had decent attack and clarity, while the synthesiser and bassline underneath were rich and warm. Sting’s vocals were as distinctive as ever despite being recessed in the mix, and as the busy production spooned on piano licks and background vocals, the Stellar Strata MK2 unpicked it without fuss.

The more downbeat arrangement of ‘Every Breath You Take’ poured from the speakers, its weighty bassline a foundation for airy synth lines and guitarist Andy Summers’ palm-muted arpeggios. This all sounded impressively big and enveloping, while ‘Breathe’, by The Prodigy [XL Recordings XLCD 121], proved much more chaotic, a flurry of angular beats, electronic bass and metallic-sounding samples.

Taste of honey

Here the Stellar Strata MK2 couldn’t do anything to finesse the ‘singing’ of frontman Keith Flint, and there was some hardening of the sound when it came to the upper frequencies, but the exuberant nature of the track was never in doubt.

Above: Three line ins (two on RCAs, one balanced on XLR) are joined by MM/MC phono, a preamp output and speaker outputs on 4mm terminals. Digital inputs include USB-B, optical, two coaxial and two I²S on HDMI sockets

Feed PS Audio’s amplifier more pristine material and it rises to the challenge. Daft Punk’s ‘Fragments Of Time’ [Random Access Memories, Columbia 0886443927087; 88.2kHz/24-bit] came across as wonderfully smooth, with gentle, well-rounded bass notes and a honeyed tone to the keyboards. Todd Edwards’ vocals were then lifted clear, providing a vivid focal point and sense of depth.

Peak performance

Another well-recorded track, ‘Synchrony’ from Kendrick Scott Oracle’s We Are The Drum [Capitol/Blue Note; 96kHz/24-bit] presented the ’Strata MK2 with a different task: digging into a smorgasbord of tones as Scott (drums), John Ellis (sax), Taylor Eigsti (piano), Mike Moreno (guitar) and Joe Sanders (bass) unleash five minutes of rapid-fire jazz as a tribute to Miles Davis. The amp conveyed the dynamic peaks and troughs, and the feeling of a band flying along by the seat of their pants, while putting the blend of sonic flavours fully on show.

On PS Audio’s StellarGold DAC all seven of the ESS DAC chip’s digital filters are retained, leaving this unit’s choice of ‘Fast’, ‘Slow’ and ‘Min’ options (available with digital inputs only, of course) looking a bit parsimonious. Alternatively, some will prefer having only three options to consider – I had no favourite so was happy to leave the Stellar Strata MK2 on its default (Fast, linear phase) setting. Of more use, perhaps, are its wealth of connections – the I2S sockets fit the manufacturer’s AirLens streamer and PerfectWave SACD player, and the balanced analogue input is there for premium outboard sources.

Above: Plastic remote offers control over the analogue and digital inputs, volume (inc. mute), balance, absolute phase and choice of the three digital filters

Adding a Hegel Viking CD player [HFN Sep ’23], over balanced XLR, and spinning Dire Straits’ ‘Tunnel Of Love’ [Making Movies; Vertigo 800 050-2] saw the Stellar Strata MK2 again impressing with the strength of its lows, ensuring this rock classic purred along with a big, rich bottom end. There was also more treble sweetness to Knopfler’s guitar licks than when I streamed the same track to the amp via USB, although on the latter connection there was still plenty of emotional heft to the ’Strata MK2’s delivery.

In the mid-section, where our guitar hero sings about ‘the Spanish city’, the song dials down the tempo and drama, bringing small percussive details and the grit in Knopfler’s vocal to the fore. It was an evocative listen, just as the subsequent guitar solo and driving drums were belted out with vigour, proving PS Audio’s amp can effectively cover all bases.

Hi-Fi News Verdict

Some will lament the absence of network streaming from this MK2 version of PS Audio’s Stellar Strata, while others will celebrate its addition of an MM/MC phono stage. All, however, will likely be impressed by the potency of its cool-running amplification. This slimline integrated never seems short of juice, and that filters down into a big and bold performance that’s sure to put a smile on your face.

Sound Quality: 84%