PS Audio Stellar Gain Cell DAC and M700 monoblock review

Separation anxiety.

We’ve all suffered from it at some point in our lives.

There are many forms of separation anxiety; the parent whose child is heading off to Kindergarten that first day, the child whose lost their teddy bear or favourite blanket, or the heartbroken teen going through a break-up, just to name a few.

I used to suffer from a different type of separation anxiety – as an adult – where I had enormous anxiety about the increase in sound quality of moving from a high-quality integrated amp to high-quality separates: I’m talking about a dedicated preamplifier and mono blocks of course.

I guess to be fair that’s more aptly called ‘separates anxiety’ though.

Over the years and after reviewing a number of separates components I’ve mostly overcome this anxiety, but since I still personally own a hand-built, lovingly NOS-tube-rolled integrated amp, there has been some hesitation to fully commit to separates or part with said integrated.

So when I spoke with Bill Leebens at PS Audio about getting the ‘Three-fer’ of the Stellar Gain Cell DAC with built-in headphone amplifier ($1,699 USD) and M700 Monoblock amps ($2,998 USD/pair) to review and (for myself) to compare to my Audio Note Soro Phono SE Signature valve integrated amplifier ($5,500 USD) and CD4.1x ($12,000 USD) CD player, he was happy to comply.

Receiving equipment from PS Audio is always a pleasure, there’s never any shipping hassles, the gear just arrives and you sign for it – an oftentimes rarity in the international shipping world when it comes to getting review gear sent out – the Stellar gear was doubled-boxed, and carefully packaged with a comfortable, ergonomic remote control and included standard-issue AC power cables.

All PS Audio components I’ve encountered (or owned) are incredibly well-built and the Stellar line is no exception. They have a weight, look and feel that exudes quality belying their sub-$5,000 USD total cost and puts me in mind of gear I’ve reviewed costing double this price point. Each unit includes a full instruction manual and brief of quality-control paperwork marked-up and signed by a real human being. The Stellar line is designed and built in Boulder, Colorado.

According to those at PS Audio I spoke with for this review – in particular CEO Paul McGowan – the Stellar line was designed and brought to production with the goal of being an entry-level set of separates that would be compact, affordable and offer tremendous value – something that PS Audio prides itself on delivering.

But I was curious, so I asked McGowan “Why start a new entry-level line with separates rather than an integrated or ‘super integrated’ which seem to be all the rage for most manufacturers these days?”

“That’s a great question,” McGowan answered. “We prefer to start out with the top of each line and then work our way down. The reasons for that are fairly simple. By starting at the top we establish the credentials of a particular endeavour, as we did with DirectStream, before releasing its more affordable brethren: DirectStream Junior.”

McGowan added that “It’s a formula that sets a standard people can come to trust and then have something to compare the more affordable follow-on versions to when they arrive.”

A little background on the Gain Cell DAC (GCD) and M700s, which come in either silver or black.

The skeletal and musculature core of the GCD centers around some crucial technologies, namely the analog Gain Cell which controls the output of the Sabre 32-bit Hyperstream DAC which PS Audio chose to handle the digital conversion duties. The whole idea of the GCD was to combine a DAC with a full-featured pre-amplifier.

PS Audio mated the delicate digital circuitry with their proprietary fully-balanced Class A (Gain Cell) analog output stage and in-house custom-configured FPGA – Field Programmable Gate Array – for the input stage. The idea behind the Gain Cell is to maintain signal integrity without putting transformers, stepped-attenuators, ladder networks or relays, etc. between the DAC and the pre-amp output: it simply varies its gain based on user-defined parameters. i.e.; volume control. It reminds me of the old hi-fi adage of the perfect amplifier credited to Stewart Hegeman of Harman Kardon notoriety: “A straight wire with gain.”

PS Audio implemented multiple power supplies for the different circuit sections as well as isolating the digital-to-analog stage circuitry from the output-stage circuitry.

The GCD features enough inputs and outputs to keep both long-time purists and audiophile newbies happy. There is I2S, Coax, optical and USB (I used the USB input and Tidal Hi-Fi with Roon exclusively for the review). Formats handled by the inputs are PCM up to 32/384KHz via I2S and Asynchronous USB, and DSD64/128 via DoP over USB and I2S (which is compatible with the DirectStream Transport “SACD handshake for DSD playback,” according to PS Audio specifications. Analog inputs are three stereo RCA pairs and one stereo XLR pair. Outputs include both RCA and XLR in the back and a 1/4-inch headphone connector up front.

Darren Myers is a key engineering, idea springboard, design, construction and voicing influence on the Stellar line, so I asked him, “What, in your mind, sets the Stellar circuit design apart from anything else out there on the market in this price category? Why is the Gain Cell technology so crucial?”

“Creating the highest performance, value-driven component is all about the optimization of compromise,” Myers said. “How do you optimize the money you can spend to squeeze out as much performance as possible? The answer is you have to figure out what truly matters. How does each component and section of a system contribute to the subjective experience? This question is the core foundation in the approach to designing the Stellar line. Everything from typology to component selection is critical in creating an affordable product that outperforms its price category.”  

“The majority of preamp/DAC combos in this price range use what’s called a potentiometer to control the volume of the signal. Although they are inexpensive and easy to implement, they tend to color the sound as well as having channel imbalances up to 2 to 3 dB. The Gain Cell replaces this component allowing astonishingly accurate channel-matching and sonic transparency. The Gain Cell also outperforms most IC volume chips that tend to have low quality, integrated op-amps in their signal path.”

One of the first things I decided to investigate for critical listening (or just completely fun, crank-some-music listening) was which digital filter to use with the Gain Cell DAC. It presents users three choices which PS Audio describes as such:

“Filter 1: Slow Roll-off Linear Phase. This filter is the least sharp and has the least amount of ringing. There is a slight loss in high frequencies that may be noticeable with CDs and other 44.1KHz material. This should not be detectable at all with higher sample-rate sources. Because it has very little ringing, we have found it to be the most musical sounding filter choice and we have made it the default filter for the Stellar.”

“Filter 2: Fast Roll-off Minimum Phase. This filter has better high-frequency response than Filter 1, but more ringing as well. There is no pre-ringing, so this is still a very musical sounding filter. Some people may prefer this filter for 44.1KHz source material.”

“Filter 3: Fast Roll-off Linear Phase. This filter also has very good high frequency response. It has slightly less ringing than Filter 2, but it does exhibit pre-ringing. While this filter may actually measure the best in a laboratory, we found it be the most analytical sounding.”

I ended up liking Filter 1, or the default setting, best overall for all types of music – it just plain rocked from Bach to Boards of Canada. This will be a user-defined setting that to me is more about the subtle flavouring of an already great dish with some very mild herbs, as opposed to dabs of Frank’s Red Hot on anything.

The built-in headphone stage has some oomph behind it with 3.25-mostly Class-A watts available into a 16-Ohm load and an output impedance of less than four Ohms. I drove a set of AudioQuest NightHawk Carbon headphones (25-Ohm impedance, 99dB efficiency) and a pair of Audeze LCD-XC (20-Ohm impedance 100dB efficiency) to great effect. The amp goosed both headphones to present real bottom-end gravitas, a clearly-defined 3D-sound field, punchy, dynamic mids with real guts behind vocals in the presence region and upper registers that always stayed shy of being fatiguing. Neither of these are what I’d consider even close to being difficult-to-drive cans, but they were what I had on hand, obviously YMMV depending on what you’re using.

M700 Monoblocks

The M700 is single channel hybrid Class A/Class D power amplifier that outputs 350W into eight Ohms and 700W into four Ohms. That’s to say, it has the ability to portray real weight on recordings. It’s the same physical size as the GCD (17x12x3 inches) and weighs in at a fairly svelte 16.5 pounds.It is kitted out with RCA and XLR inputs and has a measured THD of less than .02 per cent at 1KHz, 1W/4 Ohms. The circuit design utilizes the balanced, zero-feedback, Class A MOSFET-based Analog Cell for its input stage. Myers involvement in the Stellar GCD and M700 design saw himself, along with McGowan, focused specifically on voicing the amp to project warmth without sacrificing resolution.

Catching up with Myers in Boulder, Colorado via email I asked him about the Analog Cell and Gain Cell.

“The Analog Cell is a fully Class A discrete, MOSFET amplifier that I designed that allows the Class D output stage to sound as close to neutral as possible,” Myers said. “Similar to how we choose components/speakers in a stereo system so that they are as synergistic as possible, the Analog Cell creates a transparent and tonally accurate synergy with the output stage. It was a product of long voicing sessions conducted by Paul [McGowan] and I on the IRS V loudspeakers.  The reviews and feedback from these successful amplifiers are only proof that they are truly some of the most musically transparent and revealing amplifiers in their price range.”

“The Analog Cell is not there to hide detail from an amplifier that produces excessive amounts of non-linearity, it’s there to present a very high performance amplifier in its best light. Just like a photograph that is over exposed, the slight brightness/grayness that Class Ds produce can actually mask details such as the vibrance of tonal contrast and the naturalness of low-level nuances. The Analog Cell’s only job is to optimize this light and make the most of what is a state of the art switch-mode amplifier,” Myers said.

Knowing that Class D still seems to struggle for acceptance by audiophiles, I asked Myers “why was Class D chosen for output in the S300 (stereo power amplifier) and M700 units right from the start?  Was this because you knew the Analog Cell would interface seamlessly between the two and quell any preconceived doubts in consumers?”

“Yeah, I hear you,” Myers responded. “With the exception of a few designs that I can count on one hand, I was never thrilled with the majority of Class D designs I’ve heard. When I initially heard and measured the latest ICE Power modules, I felt confident that I could work with them. I approached Paul about using them for Stellar and he responded with skepticism but supported the idea of making a prototype to listen to. The initial prototype of the S300 was pretty darn good and we worked hard to improve it further with component and circuit modifications. I remember a specific day when Paul and I had this absolutely incredible listening session in Music Room One. We both forgot about the system and were just really engulfed in the music. It was at this time we knew we had accomplished what we had set out to achieve.”

Myers used an interesting analogy regarding amplification types in our conversation: “Throughout the 1980s and 1990’s, Redbook CD was struggling to gain momentum with audiophiles,” he explained. “It was the advancement in both the recording and conversion that allowed it to get to the level that Redbook is at today.  Class D is going through a very similar maturing process. We are just now seeing it perform at levels that challenge or exceed similarly priced linear amplifiers. I would suggest those with Class-D grudges to audition the Stellar amplifiers and discover just how far this technology has come.”

When it came to my initial ’separates anxiety’ I asked Myers if separates always trump an integrated for sound quality, frequency control and dynamics? His response was what I expected.

“An integrated amplifier today typically involves combining three to four components all in one chassis. This includes a DAC, phono stage, preamp, and a power amplifier. Since integrated amplifiers are also budget-minded, there are usually large compromises compared to their separates counterparts. This can be anywhere from a smaller power supply or output stage in the amplifier to less complex voltage regulation for the preamp/DAC. From a noise perspective alone, phono stages almost always benefit from being separate. So integrated amps can offer the best value, while separates will continue to be the top-tier performers."

COMPANY INFO
PS Audio
4865 Sterling Drive, Boulder, Colorado 80301
sales@psaudio.com
+1-720-406-8946
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COMMENTS
geoffreyvanhouwaert's picture

Thanks for a great review! Keep 'm coming!

Rafe Arnott's picture
Thanks, there's plenty to come now that the queue has filled up a bit!
Everclear's picture

More good things to come from PS audio :-) ............

Rafe Arnott's picture
Always has such high SQ and QC it's hard to not be impressed by their constant efforts to create ever better-sounding gear at a variety of price points.
Everclear's picture

"Three-fer" (three musketeers) under 5 grand .............

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