PS Audio Stellar M1200 monoblock energy amplifier

Talk about a scarlet letter. The term Class D amplification, which describes the new M1200 monoblocks from PS Audio, only exists because another amplifier innovation was already parked in the “C” room. Soon after it appeared in high-performance audio equipment, Class D became synonymous with “digital amplification,” in part because, as with early CDs, many listeners found the sound glaring, harsh, and uncomfortable. In addition, Class D is associated with “Pulse Width Modulation” and requires a low-pass filter to block high-frequency pulses that sound digitally safe. But they aren’t (see sidebar).

To this day, many audio enthusiasts are not convinced of Class D technology. Why?

According to Bruno Putzeys, one of the format’s leading innovators, “A high-performance Class-D amplifier goes against every single audiophile superstition. Designing an amplifier is the ultimate test of whether you’ve got your head screwed on properly.” Maybe because of this. Judging by the sound performance of this powerful amplifier, Stellar M1200 designer Darren Myers definitely “screwed the head on”!

Putzeys also said in the same interview with Bob Ankosko from Sound & Vision that “in class D some distortion mechanisms are noticeably missing, mainly those that relate to the input stage of a solid state amplifier of class A (B) and are non-linear capacitances that are also in the valve absence [tube] Amplifier. “So this new technology has a lot in common with old-school tubes.

Nonetheless, Myers and his team decided to implement tubes – a “full vacuum tube input stage” consisting of a 12AU7 double class A triode with no feedback, fed by its own analog power supply.

Beyond the entrance step
The US-made Stellar M1200, said to deliver 600 watts into 8 ohms and 1200 watts into 4 ohms, contains what Myers calls “all top notch components,” including PRP resistors and capacitors made by Reliable Capacitors for PS Audio were manufactured. owned by Wilson Audio Specialties.

According to Myers, the output stage is “a custom ICE power module that uses ICE’s latest ICEedge technology and significantly lowers the parasites associated with the switch mode amplifier such as high order harmonic distortion, phase distortion and output impedance instability” at high frequency. “(ICE is just as unfortunate a name for a class D module as” class D “, IMO!)

Myers told me that each MOSFET-based ICE module is “hand modified” using a process approved by the ICEpower design team to take full advantage of the vacuum tube input stage. This includes removing all semiconductor components in front of the ICEedge circuit: “This creates a simple, short and elegant signal path that combines the holographic and musical sound of triodes with the power, precision and speed of first-class switching technology.”

As with his Stellar phono preamplifier, which was named Stereophile 2020 Analog Product of the Year in the December 2020 edition, voting was done by ear. Myers said, “Rather than just tracking the best performance of the test bench, the input stage circuit design was completed by listening to the component choices, which allowed us to optimize the tonal neutrality and musical involvement that derives from the proper synergy of the input and output stages surrender. ”

Myers selected a high quality Psvane 12AU7-TII, which was hand graded and tested at PS Audio’s boulder factory. Rolling pipes is easy thanks to rear access behind a small door. I stayed with the supplied tube.

Despite its rugged performance, the M1200 is less than 4 “tall × 17” wide and weighs 27 pounds thanks to Class D efficiency. The chassis is 0.5 inches taller than the lower-powered, tubeless M700 tested by Robert Deutsch in 2018. The other dimensions are exactly the same.

On the back there is a main rocker switch, a 15 A IEC socket, two pairs of five-way binding posts (for bi-wiring), single-ended RCA and balanced XLR inputs, trigger input and output as well the cover plate for the tube access. How can something so compact and lightweight deliver 1200 watts into 4 ohms? With an over-efficient power supply that does not require a massive transformer. How can it only cost $ 5998 / pair? “We worked really hard to get those two M1200 monoblocks at a price people could afford and smile at,” PS Audio CEO Paul McGowan wrote in an email. Shipping is free and you get a 30-day home audition. After that, you can return it and get your money back. Before you decide between thumbs up or down, give this amp some break-in time: leave it on overnight every night with some playing for at least the first week.

Your bass performance is unlikely to be comparable
It’s no surprise that this super-quiet class-D amplifier excels on the floor. Bass is what Class-D was originally built for. At least it did the best and the least musical damage there.

The M1200’s ability to link, control, and drive the woofers on my Wilson Alexx speakers was on par with any amplifier I’ve had here, including my reference DarTZeel NHB-468 and the Boulder 2150, which are both much more expensive. I’m not suggesting that the lower end produced by the M1200 is the same as that; I haven’t had the boulder here for years, and the darTZeel bass is not as grippy at the bottom, but has a smoother attack and a more generous sustain that works better with the acoustic double bass.

But not on the electric bass, where the M1200 is a monster. The bottom-end performance of the 2150 and M1200 is more similar than that of the darTZeel.

I returned to Direct-to-Disc The Fox Touch (Crystal Clear CCS-7002), a data set I referenced in my SAT XD1 turntable review in the December 2020 issue. The liner notes refer to “multiple visits by the local police” during the nightly recording sessions. I’m sure if I had lived in an apartment building or if my neighbor wasn’t two lots away, I would have had a visit from the locals myself. The house trembled more than a few times at Louis Vierne’s “Finale from the Sixth Symphony”. This was also done via the darTZeels, but with the more expensive amplifier the low tones were less concentrated and more blooming. I’m not sure if I chose one over the other. A lot more money would be left in the bank if I was just looking for bass.

I pulled out the original American press of Manifesto (Atco SD 38-114), Roxy Music’s 1979 disco album that I hadn’t played in a long time. It’s a far cry from the band’s efforts, but the bass line in the theme song has always been an attraction. (The album was mixed at Atlantic Studios in New York. The George Piros mastered Atco pressing is better than the British or Japanese originals.) Two bassists are listed: Gary Tibbs and Alan Spenner; I’m not sure which of them played on the tune, but the insistent bass line was the star of the show. I’ve never heard it seem like that.

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