Herron Audio M150 monoblock power amplifier Page 2

Using the M150s was simple. Speaker connection is via five-way TIFF binding posts, and there's a gold-plated RCA jack on the rear for the input. An IEC jack allows you to play with AC cables, and there's an AGC 6 speaker-output protection fuse that you can change, depending on what power your speakers can handle. If your "audio guru" tells you such fuses are "directional," go for it! I didn't touch the fuses in my review samples.

When you flip on the rear-mounted power switch, three lights go on in sequence: The first indicates Power to the unit, the second that Voltage has been applied to the circuitry, and the third that the Output relay has been engaged and you can begin listening. If DC is present at the input, the Voltage light will blink to alert you. If the Output light turns red and the Voltage light goes out, you've overheated the amplifier (its temperature has exceeded 78 degrees C). It will shut down, and remain shut down until the heatsinks cool off by 10 degrees C.

Though I asked him not to spoonfeed me what I was going to hear, Keith Herron isn't shy about describing the sound of his amps in his product literature: "A live presentation with none of the hardness normally associated with solid-state amplifiers," along with "the fine resolution and liquidity normally associated with tube amplification plus the power and bass control of solid-state."

Herron may have smiled when he installed his amps in my system, but my own first reaction was different. Having just spent time with the Nu-Vista 300 and M3 and, of course, the Audio Research VTM200 monos, I'd become used to a big, "bloomy" soundstage and a rich midbass. In comparison, the Herron M150s sounded small and created a more distant picture. That much was immediately apparent from my less than "sweet" listening spot. So why was the designer smiling?

Herron feels that most power-amp designs add a warmth or lushness that's not present in the recording or the real world. That added sound is part of what contributes to the bloom of some gear, and that bloom helps create a false sense of a big space.

Whatever the cause, the Audio Research VTM200s produced an enormous, exciting, and enveloping soundstage, though of course its size depended on the recording. The Musical Fidelity Nu-Vista's stage was scaled back somewhat, but the Herrons' picture was the most modest and, ultimately, the most tidy. From Herron's point of view, "modest" and "tidy" are not negatives.

My perception of the Herrons' sonic picture was reinforced when I substituted his revised preamp and phono section for the Hovland, and somewhat less so when I substituted the Herrons for the Ayre K-1x. While this is supposed to be a review of the M150, I'm going to make it a review of the Herron system, because I believe that most buyers will gravitate toward the full package, even if only one piece at a time.

Different experiences
At the Y2K Consumer Electronics Show, I had been listening to a pair of loudspeakers that sounded diffuse, listless, and not particularly well-organized. Keith Herron entered the room with his unimpressive-looking amps under his arms. Out went the large, aluminum-faceplated amp with its blue LEDs, and in went these old socks of a pair of monoblocks. Suddenly, the same musical selection we had been listening to took on form, shape, and substance. Bass tightened, and there was a focus on rhythm, pitch, and texture. The difference was remarkable. The former diffusion gave way to a compact, organized, well-focused soundstage—but not an enveloping one.

A year later, the M150s and the rest of the Herron gear produced the same sound in my system, but now my reaction was mixed. One of the things I admire most about the Sonus Faber Amati Homage speakers in my new, well-treated listening room is the grounded soundstage I get. The experience of sonic images "floating" in air without legs bothers me; among the few negative observations I have about the Herron system (and about the M150s by themselves when I drove them with the Hovland or Ayre preamps) is the imaging and soundstaging they produced: pictures floating in air.

When you're in a jazz club, you hear a combination of direct and floor-to-ceiling reflected sound; superb live recordings like Mel Tormé and Friends at Marty's (Finesse W2X37484) should put you convincingly in the club where they were recorded. When I listened to the M150s with the lights out and my eyes closed, three (or more or fewer, depending on the recording technique) well-focused spheres of sound hovered across the soundstage. The entire picture floated off the ground, and that sensation remained constant whether the music had been recorded with three spaced omni microphones, à la Mercury Living Presence, or the multi-miked production used for the Tormé album.

It could be argued that this homogenization of the amplifiers' soundstage could have been speaker- or room-related, but the speaker placements were made according to RPG's computer program, and have proved ideal for all speakers and electronics I've reviewed in the room. I certainly didn't position the speakers to complement or "frequency-balance out" my reference amplifiers.

Herron Audio
12685 Dorsett Road, #138
St. Louis, MO 63043
(314) 434-5416