Doug Schneider - DAS

May 1997

A Switch to Digital?
Spectron 1KW Amplifier

I have never been an audiophile who subscribes to notion that only a certain amplifier technology will deliver musical sound. Does your amplifier really have to have tubes? What about all those sweet sounding solid state amps? Is single-ended now the only way to go? There are even single-ended solid state amps too! The way I see it, if any one of these assumptions is correct, then the rest must be wrong. Somehow I doubt that. The application of technology is really the key since there are a number of fine sounding amplifiers that use very different design principles.

I am the first to admit that I rarely get jazzed over amplifiers. Speakers? Yes. Source components? Yes. Just about everything else? Yes. But for some reason amplifiers just do not generate the same excitement in me. Don’t get me wrong, I don’t believe all amplifiers sound the same. They don’t. It is just that I usually find bigger sonic differences between, say, speakers or even CD-players, than I do between very good amplifiers. Furthermore, I have yet to find the perfect amplifier that is the ideal partner for all speakers, all music, and all rooms.

Recently I have had the opportunity to listen to a number of amplifiers. Three of these amplifiers, in particular, have left an impression on me for one reason or another. Furthermore, each of them has employed much different design technology. The Clayton Audio M-70 monoblocks are 70 watt solid state, Class A amplifiers that deliver beautifully sweet highs, tight bass, and astonishing clarity. The Blue Circle BC-2 amplifiers are also monoblocks that deliver about the same power (75 watts) but are a single-ended design. While their output stage is solid state, a single tube per channel is used for voltage gain. Their virtues? Highly detailed, transparent, powerful, tonally rich, and wonderfully musical. The third amplifier is the Spectron 1KW. An amplifier that is not only technically different from the first two, but is vastly different from the majority of the amplifiers on the market today.

The 1KW is a digital/switching amplifier and is designed in the US by Mr. John Ulrick. Although this is the first time I have been able to audition an amplifier of this type, the technology has been around for many years. Spectron, it seems, is at the forefront when applying digital/switching technology to high-end amplification. As a matter of fact, John Ulrick designed his first amplifier of this type at Infinity some 25 years ago (he started the company with Arnie Nudell) . However, my understanding is that components required to create a high end worthy digital switching amplifier have been unavailable until recently.

Now don’t get confused by thinking that the 1KW outputs some sort of digital signal that needs special speakers to match it to. The output, as well as the inputs, are pure analog. The digital reference pertains to what happens inside the amplifier to generate its power. Suffice it to say that I am not technically inclined enough to describe to you exactly what digital switching means, rather, I will quote the only portion of the Owner’s Manual that makes reference to it:

"Spectron’s digital power amplifiers converts the audio input into two digital pulse width modulated (PWM) signals to control the two output switches. These two switches generate a 500 kHz, 160 volt peak to peak pulse width modulated square wave which contains two components; the 500 kHz carrier plus the audio signal. In turn, this modulated carrier is passed through a low pass filter which blocks the high frequency carrier but pass the audio signal on to the amplifier’s output."

What is immediately apparent is that this technology results in tremendous amplifier efficiency. The 1KW is only 17 inches wide, 3.5 inches high, and 12.5 inches deep. There are no external heat sinks, but it does use a front mounted fan (just behind the frontplate) to draw air through the chassis for cooling. The fan runs quietly (I could not hear it during listening) and it adjusts its speed to maintain the amplifier at a 40 degree Celcius operating temperature. This compact, dense unit delivers 300, 500, and 500 watts into 8, 4, and 2 ohms, respectively. Overall, this is quite impressive given its size, however, it should be noted that the power does not increase into a 2 ohm load. Many of todays ‘muscle amps’ keep powering up into the lower impedances. Still, this is a very powerful amplifier that should satisfy all but the most watt-hungry of audiophiles. Spectron claims 93% power efficiency from their switching output section. The 1KW comes with both single-ended and balanced inputs. The retail price of the 1KW is $3495 which makes it somewhat of a bargain in the world of high-powered, high-end amplifiers.

There are a couple aspects to the 1KW that make it visually ‘different’ from most high-end amplifiers in this price range. The first is the large gold knobs on the front that adjust the gain of the amplifier. These actually have a useful function in that you can directly attach your source component (such as a CD player) and use the gain knobs as dual volume controls. Of course, this would only work if you did not need the source switching capabilities most preamps provide. Spectron recommends having the knobs set at full gain for best sonic performance. What degradation occurs when the gain is set lower than full may be offset by the elimination of a preamplifier stage. Newform Research used the Spectron like this in their display at the recent audio show in Montreal and the sound was very good. I did no tests as such. Instead, I used my Blue Circle BC-3 preamp in between the Theta Data Basic and Prime II DAC source.

There are also voltage and current indicator lights that display a type of power bar-chart on the front. While they do provide a useful indication of how hard the amplifier is being ‘taxed,’ some audiophiles may be turned off since indicators such as these normally spell MID-FI. I’ll admit, I found them nifty.

At this point I would like to mention that the 1KW also has a little brother called the Digital 1. The Digital 1 reportedly has the same electronic guts, but eschews the gain knobs, meters, and cosmetic frills and retails for about $1000 less (in US dollars). I only had the 1KW on hand so I could not compare the sonic performance to verify this.

The Spectron 1KW is, by far, the most powerful amplifier I have had on hand in recent times (actually, come to think of it, that I’ve ever had on hand). I own a Classe Fifteen amplifier and that is what I did most of my comparing to. Classe has since replaced the series that the Fifteen belonged to with the new ‘CA’ models. I have heard these new models and while there are some aspects of performance that ‘may’ be better, I rate the performance as different. The Fifteen may be a few years old, but it is still regarded as an exceptional amplifier of great musicality and power. So too are its series brethre -- the Twenty Five, the M-700, and the M-1000, among others. Should the Spectron outperform the Classe, it would indicate that it too is a very good sounding amplifier.

The specs say that the Fifteen provides 175 wpc into 8 ohms, 350 wpc into 4 ohms. While not the powerhouse that the 1KW is, it is still a very powerful amplifier. Furthermore, no speaker I have on hand comes close to pushing either of these amplifiers to their maximum power. The 1KW’s second indicator light (out of about ten) barely ever winked at me. This provided a useful indication that the Spectron amplifier was humming along with minimal effort into the Newform Research, B&W, Coincident Technology and other speakers I used it with. My listening, then, was not a test of power. It was a test of musical finesse.

The 1KW has a distinctive sound that is not difficult to recognize. It is lightning fast, transparent, and highly focussed. As well, it has full and detailed extension from its rock-solid, heart stopping bass through to the highs. The term I have been using to describe its performance is ‘visceral’ sounding.

It was easy for me to hear why Newform Research is the Canadian Distributor for Spectron. The R8-1-30 is an excellent performer in its price range ($1236), however, I found the R8-1-30 sounded a little too robust in the upper bass, lower midrange area. While my Classe easily drove the Newform R8-1-30 loudspeakers with a rich, full, and laid-back sound, it was the 1KW that snapped that entire loudspeaker into sharp focus. The combination sounded great. Subjectively, the Spectron gave the sonic impression of grabbing hold and maintaining full control of the loudspeaker, whereas the Classe sounded a little ‘looser.’ Bass performance of the two amplifiers went equally deep, however, the Spectron had significantly more impact and ‘slam.’ Where the the Classe was rich and full bodied, the Spectron was taught and dynamic.

Imaging and depth through the Newform speaker was more distinct and impressive with the 1KW. In comparison to the Classe, the 1KW tended to place vocalists slightly in front of the speaker plane. At the same time, rear-hall ambience and instruments located deep into the stage were placed further back with an increased sense of separation and layering. With Newform’s ribbon/dynamic hybrid, the Spectron was by far the better match. Furthermore, these performance attributes of the Spectron held true through the rest of my auditioning with different speakers, but with different results.

Next, I paired the Spectron with the Coincident Speaker Technology Conquest loudspeaker. The Conquest is an easy load with fairly high-efficiency (about 92dB). Even amplifiers of insignificant power can fire them up to impressively high levels. The Conquests also have a little bit more treble energy than other speakers I had on hand. This, coupled with the Spectron’s more forward and visceral balance, was just a little too much of a good thing. The Conquest can sound impressively detailed and musical in the right system. In this case they sounded too forced and in your face. The Classe driving the Conquest sounded more laid back and could be called ‘lush’ by comparison. In the end, the Classe proved the better match. I should tell you, though, that I have heard much better performance with the Conquests and smaller tube amplifiers, such as the Golden Tube SE-40, than with either of these amplifiers. This is a good example of why careful component matching is mandatory to build a great system.

My experience with the B&W 803 Series 2 loudspeakers mirrored that of the Newform. In this case, however, the Spectron was not as clear of a winner. The sonic differences were apparent, but not as much as with the Newform loudspeaker. I did sense a little too much treble energy with the Spectron (this has been a criticism of the 803 with other amplifiers as well), but it was not off-putting like it was with the Conquest. Again, the Spectron seemed to have more control over the loudspeaker that resulted in a faster, tighter, more rhythmic presentation. The 1KW has an uncanny ability to ‘grab onto’ to a loudspeaker and focus it in which I find attractive. However, some people may be put off by this type of performance since it could, on the wrong loudspeaker, sound a little too forced. In the right environment, like I heard, it can work wonders.

There is no doubt that the Spectron 1KW is a unique and high performing amplifier. It also sounds like no other solid state amp that I have heard before. Is it the amplifier for every occasion? I don’t think so. But there are situations where I can imagine that the Spectron would be a killer. First off, its high power rating, compact design, and reasonable price tag make it an impressive choice for those who need a high powered amplifier. This is especially true if you consider that the no-frills Digital 1 retails for $2495 USD. Furthermore, the 1KW was an eye-opening experience for me due to its ability to present an enormous amount of musical detail and for its exceptional coherency. It achieved this without sounding edgy or bright. Overall, The 1KW has a tight, focussed performance with an excellent sense of rhythm and pace that will excite many listeners. On top of that, the 1KW can produce taught, "thunderous" bass like few amplifiers I have heard. While this type of performance may be too ‘visceral’ for those who prefer a more lush, laid back and ‘blooming’ presentation, the Spectron proved that it can match synergistically and produce exceptional results in the right system. For that reason alone, it should be heard.

...Doug Schneider
das@sstage.com