Primare A35.2 energy amplifier | Stereophile.com
My desk looks out over a large garden with chickens, bees and wild cats. My chair is only three feet from the speakers and plays softly to my left. The picture I’m working on sits between the speakers. The painting hangs no more than 10 feet from the oscilloscope and drill in my kitchen. Best of all, my desk is only three feet away from clusters of voracious sparrows attacking the suet cage on the fence outside my window. These real-life attractions keep my right and left brain in balance. Similarly, reviewing both analog and digital sources, and tube and solid state amplifiers, keeps my review practice balanced. But not always. Sometimes my Apollonian self struggles to balance my Dionysian self. Especially when checking class D amplifiers.
You see They see. . .
Class D amplifiers are about quantities: like high power with high damping factors delivered in small, lightweight boxes at low temperatures in small, lightweight boxes at low prices per dollar. Class D is a left brain treat that states, “Look what a smart shopper I am.”
Class D enthusiasts revere Bruno Putzeys, the Belgian engineer who boosted Class D’s current popularity, first with his UcD power amplifier module for Philips and then with his NCore amplifier modules and various switching power supplies for Hypex.
I’ve always been a fan of Bruno’s Class D modules because they deliver exceptionally clean, dynamic performance at very reasonable prices. Best of all, Hypex not only makes these modules available to other manufacturers (such as Bel Canto, NAD, and MBL), but also as kits that are made available to DIY enthusiasts. If you look at the bigger picture, you can rightly say: Putzeys’ inventions are currently changing the landscape of high-fidelity audio.
For me, the main beauty of class D is: it brings the specter of upper class sound into commercial class salons.
Class A, on the other hand, is about qualities. Class-A has long been preferred by nobles and appeals to right-brain audiophiles with a penchant for sensual excitement and leisure. Think stone fireplaces, linen sheets and wines from Châteaux. Like aged drinks, Class A warms the listener’s blood. Class A amplifiers are typically low power, housed in a heavy package, and operate at high temperatures.
But times are changing. Young royals have begun to abdicate. And class D amplifier manufacturers are looking for royal warrants.
Class D amplifiers tiptoe into the lord and lady’s listening chamber. They sneak in because they are presented in restrained, fashionably shaped chassis at prices on Oxford Street. The subject of this review, the $ 3495 Primare A35.2 stereo amplifier, is one of those new breeds of fashionably shaped, “gentrified” Class-D amplifiers. My plan is to see what it sounds like when I sip on Châteaux Margaux.
Sequence is everything
The only way to check a basic amplifier is to take out the amplifier that controls the speaker in the system and replace it with the amplifier I want to check. My review deadlines are always the 10th day of every month. So I usually plug the new amplifier into the speaker on the 11th or 12th day that was in the system at the end of the verification period. My first hope is that it will work, that some form of relatively undistorted sound will come out in equal parts from both channels. In that case, I can relax: as long as the amp doesn’t catch fire or blow fuses, I’ll likely make my shilling and three pence for the month.
On December 11th, 2019 I connected the just arrived (from Sweden) Primare A35.2 amplifier to the Magnepan .7 quasi-ribbon panel speakers. The .7s have a power-hungry nominal impedance of 3 ?? 4 ohms which I assumed would work very well if driven to 4 ohms by the A35.2’s 400Wpc. And I was right. Immediately the humble Maggies from both channels made a clear, undistorted sound, which allowed me to relax and listen carefully to Alexandre Tharaud’s faux cabaret album Barbara (24 / 44.1 FLAC Erato / Qobuz). This recording, an homage to a Chanteuse Française known only as “Barbara”, is a 2019 favorite of mine. It is well received and sounded particularly well articulated over the A35.2.
The sound was good and the transparency of the A35.2 was noticeable, but the Primare amplifier sounded very different from the 20 wpc Schiit Audio Aegir amplifier it was replacing. With the Primare Amp and Maggie .7s, this well-made recording presented Alexandre Tharaud with a very clear outline. The lower register of his piano became firmer but less resonant. Tharaud’s voice took on a well-articulated but slightly unobtrusive quality. The Primare made the aegir sound grainier and slightly hazy.
I was surprised too because every time I muted the Primare amplifier to make a call or open the door, the damn thing would shut off! It would start again when I hit the standby button, but the ordeal was annoying. When I checked the A35.2’s online manual it said, “If there is no signal for 20 minutes, by default the A35.2 will automatically go into standby mode to save power.” The manual also says, “To turn off automatic standby mode: press and hold the button on the front for a few seconds and release it when the indicator light flashes twice and stays on.” That was easier said than done. Later (shown below) I discovered a switch on the back that made this 20 minute standby scheme a really enjoyable feature.
The Primare A35.2 is a stereo amplifier weighing 26 lb, measuring 5.7 “high × 16.9” deep × 15.7 “wide, and features Primare’s proprietary UFPD2 Class-D analog -Application technology “designated power, the 200 Wpc at 8 ohms provides the ability to be easily bridged in mono for 800 W (!) In 8 ohms.
On the back there are two 3.5 mm sockets for the input and output of a 12 V trigger. one RS232 input; a pair of cinch and XLR inputs each (balanced); and of course right and left speaker wire tie posts. There are also a number of four small toggle switches. The first switch turns the input sensor on and off so that the amplifier automatically switches from standby mode when an input is detected. (Your ladyship liked that.) The second switch switches between symmetrical and single-ended inputs. The third switches between two-channel and bridged-for-mono operation. And the fourth allows normal gain or a gain of +6 dB (the latter only in bridged mode).
Primare style of class D.
According to the design letter I emailed from Terry Madalen, Primare’s representative, “The main reason we invented Class D was efficiency, and many of the performance benefits that come from strengthening Class D, are the result of the significantly higher capability of some class D amplifier manufacturers not realizing the full potential this technology can offer, but our amplifiers combine the latest in efficiency with the state of the art in audio performance . “(As I read these SOTA claims, I had an urge to add a snappy remark, but held back.)
The design description went on to explain why Primare believes the A35.2 is superior to other Class D amplifiers:
“One of the main sources of distortion in Class D designs is the output demodulation filter, which becomes unstable with changes in speaker impedance unless controlled by adequate feedback. Insufficient feedback is provided to accommodate dynamic changes in speaker impedance across the audio to manage something.” The band causes the THD to increase with frequency. While it sounds very dynamic and lively at first, it can become exhausting and uncontrolled in the long run, especially when driving complex loads.
“UFPD provides a consistent feedback loop gain of 26dB across the audio range and is stable well beyond the audio band. Instead of using the amplifier and then the filter as discrete stages, the UFPD design integrates both, making control with feedback much more immediate and exactly. ”
I asked Terry who designed the A35.2:
“We design our products by employing consultant designers with specific talents in various building block components to design each product. So in the case of A35.2, it is a product of Patrick Bostrom’s particular expertise in developing Class D power circuits (Sweden) and in the case of power supply Björn Sandberg (Denmark) Bent Nielsen (Sweden), our chief engineer since the company was founded, then work with their basic designs so that they can work together in the most pleasant way within a product – capable and elegant design. ”
According to Terry, the UFPD2 (amplifier) and AFPC (power supply) modules as well as the chassis are manufactured by “our OEM manufacturer in China”. When I asked where the A35.2 is mounted, he said, “In one of the largest and most modern OEM manufacturing facilities in China, with the final quality control tests being done in our factories in Sweden.”
More hearing about Magnepan .7s
After a week of casual listening, I got a good feel for the Magnepan .7 powered by the Primare A35.2. The nice thing about Magnepan’s quasi-ribbon panel speakers is that they are not wooden boxes with dome tweeters and they generate an enormous sound field. Best of all, they go away when I close my eyes. The silence of the A35.2 amplifier made the quiet Maggies disappear more than usual.