As Canada's Radial Engineering continues to revive the Hafler brand (acquired in 2014 from Rockford Corporation), its latest move is into power amplifiers. First out of the gate is a revival of Hafler's lateral MOSFET "Trans•Nova" amplifier design, last seen in the classic Hafler 9500 THX-certified amp of the mid-1990s.
The P3100 amplifier, which delivers 150 Watts per channel into 8 ohms, updates the original design with a toroidal power transformer, balanced and unbalanced inputs, and modern speaker connectivity. It also includes a rack-mount faceplate. Radial claims the toroidal transformer "has a lower output impedance and produces far less noise than a conventional E-lam transformer. The result is a tighter, more defined bottom end. As well, toroidal transformers are inherently self-shielding, which reduces the amount of potential low frequency and rectifier noise introduced into the audio signal path."
The amp is substantial and heavy, with large heat sink fins running along the sides (no fans, hence the amp runs silent and can be placed anywhere in a studio or listening room). In my time using it, the amp got warm but never hot to the touch. Speaking of temperature, the manual recommends a warm-up time of about an hour in order to reach thermal stability. My ears did prefer its sound after proper warm-up. The P3100 can be set up for bridged-mono output of 400 Watts into 8 ohms (for instance to power a subwoofer or as part of a pair driving very large or inefficient speakers) and delivers 200 Watts per channel into stereo 4 ohm speakers. It has more than enough damping factor and excursion control to protect just about any speaker I've ever heard of.
On the front panel is a plastic rocker power switch, LED output meters, and level-trim controls. The amp's manual suggests these trimmers are only intended for balancing speaker levels (in case one channel needs to be turned down for proper sound presentation or to correct room imbalances) and should otherwise be left wide open (clockwise), with system level controlled by the connected preamp or mixer. That's a good thing because the right trimmer on my test unit introduced a low-level hum if it was turned at all counter-clockwise. I assume this is a part defect rather than a design flaw. I made sure to check if the hum didn't occur with various different hookups of speakers and source devices, but it remained, so I'm going to say it's baked into that particular trimmer or associated circuit. Hafler immediately offered to replace the entire unit, commenting that my P3100 was one of the first runs off the assembly line. They have assured me that, as of publishing, more rigorous test procedures have been introduced to ensure this doesn't happen again.
Aside from that minor issue, this amp sounds good. It had more than enough power to drive my large but pretty efficient B&W 808 speakers, and also my Amphion Two18 monitors [Tape Op #108]. The amp easily managed both speakers' impedance ranges and tightly controlled the low end reproduction. I was happy with its sound throughout the audio range, and it had a silent background.
The Trans•Nova design is interesting in that it uses fewer parts and gain stages than typical bipolar transistor designs. It was invented and patented by Jim Strickland in the 1980s, and Hafler's website includes a link to Strickland's paper explaining it. There is also a simple technical explanation by Stereophile Magazine's John Atkinson that can be found on their website.
Back to the P3100; I had it hooked up in both my studio (with the Amphion monitors) and in my cathedral-ceiling living room (with the B&Ws). I also hooked it up in parallel to three pairs of cheapo 8 ohm speakers, to see how it handled really low-impedance loads (it did fine, didn't even get very hot, and never sounded like it was having any trouble making those speakers as loud as I wanted to hear them).
In both the studio and the living room, the amp sounded fast and capable with any style of music. I wouldn't call it as transparent as my Benchmark Systems AHB2 power amp [Tape Op #111] nor does it run as cool. But the Hafler "sound" is not unpleasant. I would call it somewhat "forward" and slightly "punchy" but definitely not "warm" or laid-back. It's not harsh, like for instance an early era Altec Lansing or vintage Crown Audio solid-state amp, and I would call its "sound" quality minimal versus many amps of a decade or two ago. Looking at reviews of the Hafler 9500 from the 1990s, many noted how "transparent" and "honest" it sounded.
I found the P3100 useful for QC listening and mixing/mastering decisions. If I didn't own and know the Benchmark, I would probably consider the Hafler as transparent-sounding. If you swap the Hafler in for many of the older amps now driving big soffit-mount speakers in control rooms, I suspect you'd hear comments about greater clarity, bigger soundstage, and greater low-level detail. I also suspect that this amp would be more comfortable driving vintage studio monitors, even Altec Lansing 604s (known to be maximally screaming and harsh when driven by some solid-state amps common in the '70s and '80s), than many other solid-state amps. Hafler markets the amp for the pro studio market, but it would be right at home with an audiophile home system set up to be on the more neutral/uncolored side of things.
The revival of the Hafler Trans•Nova amp fills a need in today's market. On one side, we have ever-cheaper and ever-more efficient class D designs (most often heard in powered monitors and live sound applications). On the other end, the audiophile market is now filled with pricey amps (both tube and solid-state) designed to have a "personality," and are not necessarily designed for accuracy and transparency. It's good to have a proven class AB design back in circulation, at a reasonable price point, that's known for being both musical and accurate.