Solid State Power Amp Reviews

As JGH suggested in his glowing review of the $3999 Boulder 500AE, this manufacturer has not (until now) been considered a serious contender in the high-end audio marketplace. I've seen scads of Boulder amps in studios while playing on recording sessions, but never took the time to really listen. So when I ran into the people from Boulder at last January's CES in Las Vegas, they were quick to accommodate my request to sample their wares in my own system. A pair of 500AEs arrived while I was preparing a review of the Cello Palette preamplifier, and were immediately put to work. I listened to one unit in stereo for a few days, then added the second for dual-mono operation. Unfortunately, one of the amps suddenly died on the fourth day (power stayed on, but no signal was passed), and was immediately replaced by the manufacturer. I should note at this point that Boulder claim their amplifiers are among the most reliable in the pro recording industry; my misfortune must have been a fluke. Better it should happen to a reviewer than a consumer.

When I read through JGH's evaluation of the 500AE, the first thought that crossed my mind was that poor Gordon had taken leave of his senses. Everything I'd ever heard about Boulder amps from people in the high-end audio community was not very flattering: built like a tank, but short on finesse.

Well, I'm here to tell you that JGH has not lost his mind or gone deaf—everything he said about the 500AE was dead-on accurate. If anything, he understated this fabulous amplifier's attributes. Since Robert Harley has already contributed a "Follow-Up" on the 500AE's single-unit stereo performance, my comments here are mainly concerned with operating two amps ($7998) as a dual-mono pair. However, a few observations concerning stereo operation are in order.

There are some colorations (slightly bright and forward, with a distinct nasal quality) inherent in the sound of a single stereo 500AE that totally disappear in dual-mono. Don't ask me to explain why, or how. It just sounds much more neutral and transparent with two vs one. In fact, you really haven't heard this amp until you go the dual-mono route. Sure, it's twice as much money, but the dramatic difference is definitely worth the bucks.

Another important thing to note concerns the matter of input phasing. Just about all pro recording equipment I've seen, as well as home consumer electronics with balanced inputs and outputs, use pin 2 as positive absolute polarity (referred to as "hot" in studio lingo), pin 3 in mirror-image reverse polarity, and pin 1 to ground. Boulder, and I believe Jeff Rowland, are the only manufacturers to use pin 3 as hot.

What does this all mean sonically? Plenty. Unless the rest of your system is compatible with this, or you reverse the absolute polarity at your preamplifier source component, or loudspeakers, the resulting sound will be out of absolute phase, which could compromise soundstaging and the clarity of transient attacks. Why Boulder has chosen this route is a mystery to me. Every balanced-operation microphone, mixing board, active speaker, and studio amplifier I've seen has used pin 2 as hot. Perhaps Boulder will see the light and change their products to conform to the rest of the industry.

So what's so great about the dual-mono 500AE? Everything and nothing. If you want to hear exactly what went on during the recording session, good and bad, then there really isn't any alternative. However, if the truth intimidates you, or you prefer candy-coated sound, stay away. JGH used his own master tapes as a reference in his evaluation of the 500AE. I've done the same, although in my case, I played the music rather than produce the recordings.

Gordon brought up some important points in his review, especially in regard to soundstaging. What most people don't understand is that, except for those few instances where the engineers have taken the trouble to capture natural phase-coherent imaging, soundstage dimensionality is created, not re-created. Many engineers inject varying amounts of delay (digital or analog) to produce the illusion of depth. The more delay, the deeper the soundstage appears to the human brain. It is also common practice to use several air mikes well out in the concert hall to create additional dimensionality.

Up until the appearance of this amplifier, I couldn't always discern between real and contrived. I sure can now. Artificial ambience and depth stick out like sore thumbs with the 500AE, making several recordings that I thought were pretty good sound like canned music with lots of reverb added. Not very satisfying. But when the recordings really had depth and space, this amplifier projected a soundstage extending far beyond the boundaries of my small room. Many other amplifiers (especially those with tubes) certainly produce a more pleasing sense of space all of the time. As a musician, I can tell you that Gordon was right when he stated that live music doesn't necessarily have that enormous sense of depth when heard in the flesh. If you want bigger-than-life dimensionality, don't even bother listening to this amplifier. But if you frequent the local concert hall, and use the real thing as a reference, missing the opportunity to hear soundstage faithfully reproduced would be a serious mistake.

Some listeners, including RH, find the 500AE to be too forward and vivid. It is not. Microphones do not perceive sound as the human ear does, and different mikes produce different listening perspectives. For example, the Neumann M-50 (tube) and TLM-50 (solid-state) microphones are both basically omnidirectional in nature, but with a very definite on-axis upper-midrange emphasis (more so with the older M-50 than with the current TLM series). Recordings produced with these microphones can sound quite forward, and downright brash. Many of the older Deccas engineered by Kenneth Wilkinson (with whom I made several recordings with the NSO in the 1970s) used five M-50 mikes (three on the central tree, with an outrigger on either side). For instance, Wilkie's recording of Richard Strauss's "Dance of the Seven Veils" from Salome (Antál Doráti, Royal Philharmonic, Chesky CD36) has a very forward perspective. It's almost too much with the Boulder 500, but I love it. The same thing goes for the cycle of Shostakovich symphonies we've been recording with Teldec. The TLM-50s they use for main pickup place the listener about 15' behind the podium. That's the way that it should sound. Not laid-back or pleasant, but up-front, visceral, and V-I-V-I-D. If you don't like this, then the 500AE isn't for you. But isn't the whole thesis behind high-end audio supposed to be the art of capturing everything on the master tape, without editorial comment?

I have to also agree with Gordon in his assessment of the low-frequency impact and vise-like control the dual 500AEs exerted over the speakers. When the program material had the guts, this amp really kicked butt—picked the speaker up and threw it across the room. Or, as they say in the jungle, "Me Amplifier, You Speaker." But give it a string quartet, or a pianissimo solo voice, and the sound was sweet, warm, and liquid. Of course, all of the above is dependent on all other components being of similar quality. If you've got a dog of a preamp, or your interconnects are the cheapest that Radio Shack sells, the 500AE will unmercifully expose the weakest link.

JGH hit it on the head when he said that this is not an audiophile amplifier. Maybe it's just too honest. I can now understand why so many engineers and producers prefer the 500AE. If I were going to make a recording, you better bet that I'd use this one. If one wants to hear everything that was put down on tape, it's imperative that the entire chain, from source to loudspeaker, be as neutral and sonically invisible as possible. Most audiophiles will probably agree with this, in spite of the fact that many really don't want to hear their music straight up.

All of this brings up an important point. One of my colleagues, bass trombonist Bob Kraft, also runs a recording business. Bob felt that, while the 500AE would be the ideal amplifier for sessions, he might not want to listen to it all the time in his home system. Given the choice between the Krell KSA-250 and the Boulder 500AE, he mentioned that he just might take the latter for work, the former for enjoyment. I have to agree, to a point. The KSA-250 remains a favorite: very transparent and dynamic, with few colorations. A truly great amplifier. In the absolute, the Boulder 500AE is "more accurate," albeit not necessarily as enjoyable in all circumstances. It doesn't exaggerate anything (although those people not used to hearing everything might disagree), nor does it subtract. In other words, you hear the recording, not the amplifier.

Needless to say, I heartily agree with JGH's observations concerning the 500AE. It is the least colored, most honest amplifier I've heard. Recordings in which I performed simply sounded more "real" and "live," with no trace of electronic editorialization. Of course, the good also comes with a downside. Less than perfect source components and recordings will not get away with musical murder as easily as with lesser amplifiers, and you may just find that the rest of your system simply isn't up to the task of dealing with such honesty. If you're into designer sound, and want something that presents the music in a way you would like to hear it, this amplifier would be a poor choice. But if you want to get every last detail, capture every nuance, and want nothing between you and the recording, the Boulder 500AE amplifier operated in dual-mono is at the top of the list.—Lewis Lipnick