Solid State Power Amp Reviews

If we had been asked some time ago to describe our "dream amplifier," chances are we would have described the Crown DC-300. Designed originally as an industrial device, it was made available as an audio amplifier rather as an afterthought. But if that roundabout approach is necessary to produce an audio amplifier like this, so be it.

We thought we had heard virtual perfection in power amplifiers before. The SAE Mark II, for instance, produced such beautifully lucid, effortless sound that we honestly believed further improvement would be superfluous. It isn't.

By comparison, the DC-300 is a shade more lucid, tighter at the low end, sweeter at the top, and considerably more effortless when reproducing at high levels. Wake no mistake, the difference is audible, even at low listening levels. And when we compare the DC-300 with other available power amps (besides the SAE), the difference is almost beyond belief. In most cases, it as though a subtle (or unsubtle, occasionally) veil has been lifted, allowing one to listen to the music instead of at it.

Of particular interest is the effect of the DC-300 on low-end performance. We found that, in some cases, switching from any other amplifier to the DC-300 tightened up the entire low end to a degree that was downright dramatic. Loose, wooly, somewhat boomy low end suddenly became detailed, controlled, and well-defined. In other cases, the improvement was so subtle as to be almost inaudible.

The difference, as it turned out, was a function of the particular loudspeakers the DC-300 was used with. Systems which normally tended to be rather heavy and ill-controlled at the low end were most conspicuously improved, while ones that normally—that is, with most other amplifiers—yield a tight, detailed low end showed the least improvement there when driven by the DC-300.

There's not really much more to be said about its sound, because the DC-300 appears to be entirely without any sound of its own. And if we have ever said this about any other previous power amplifier, it is only because we had never heard the DC-300. But it does raise a question which we are not sure we want to try to answer just yet. Namely: Have we been doing some sort of a disservice to some loudspeakers we tested in the past, by not testing them with the DC-300? Would some systems that were faulted for booqy bass have sounded satisfactory with the Crown? Certainly, we can justify our mistaken (?) judgements on the basis that there was no DC-300 until relatively recently, so we had to judge them on the basis of what amplifiers were around. And we might be excused for taking the attitude that nobody in his right mind is going to spend almost $700 for an amplifier to drive two $50 loudspeakers.

But the question remains: Should a loudspeaker be judged on the basis of its potential performance, or on the basis of its performance under what might be considered "realistic" conditions of use? Perhaps both approaches are in order, but as we said, we won't try to decide now.

It is obvious that, on the basis of price alone, the DC-300 is not for every home-hi-fi hobbyist. And for those who can afford it, it is not without potential problems. For example, it is one of the few available power amplifiers with power enough to devastate most loudspeakers. Using the DC-300 with a pair of 30W-capacity speakers, without protective fuses, is simply asking for a catastrophe, for all it takes is one loud pop, from a noisy switch or an ungrounded phono input or a stylus touched delicately to the rough edge of a disc, and $600-worth of loudspeaker can go up in a puff of smoke. You may think you can avoid trouble by "being careful," and you probably can for a while. But if two 5-cent fuses can buy peace of mind, they're worth it. Recommended fuses are listed in the instruction manual. Follow the recommendations.

An Honorable Mention
The manual, by the way, deserves an honorable mention, too. This was obviously written by engineers for engineers, and while the sections on installation and use are clear enough to be of value to the average nonsophisticated hobbyist, the rest of the manual provides just about all the information that any user could conceivably need.

To the hi-fi buyer accustomed to the usual consumer-type instruction manual, this one will be a revelation. The manufacturer claims that the DC-300 is "protected against all the common hazards which plague high-powered amplifiers," and as far as we could determine, this was the case. The manufacturer warns that damage can and will occur if the two "hot" output terminals are connected together, but this is not at all likely to happen accidentally. Ve tried all the usual accident-type things in an effort to get the amp to self-destruct, but it didn't. When presented with an impossible situation, it just shut down temporarily or popped a fuse.

Enter the Nines
One loudspeaker system that this amplifier almost seems to have been designed specifically for is the KLH Model Nine. The DC-300's distortion is low enough to expose to the Nine's unsurpassed transient response, it appears to be completely stable with the Nine's highly reactive loading, and its power capabilities are a perfect match for the Nine.

A single pair of Model Nine panels have a nominal 16 ohm impedance and a power capacity of 100W per panel. The DC-300 will deliver almost exactly 100W maximum per channel into a 16 ohm load, and when two KLH Nine panels are paralleled in a four-panel system, the resulting 8 ohm load allows the amplifier to deliver almost 200Wpc, which is still close to the rated capacity of the speaker system. Consequently, no protective fusing is necessary with the Nine, although it is necessary to add large isolating-capacitors to the speaker lines to prevent the Nine's step-up transformers from shorting out the amplifier at subsonic frequencies.

Issues
Unlike many solid-state power amplifiers, the DC-300 produces no click or thump when turned on, which is nice in view of its destructive capabilities. Some preamplifiers and tuners do however produce loud switch-on pops, and a few of them (the Dyna PAT-4, for example) will pop if the input selector switch is operated during the first several seconds after switch-on. For this reason, even if the loudspeakers are fused, it is a good idea to turn on the preamp and tuner first and then wait a few seconds before turning on the DC-300. This could save you some money on fuse bills.

An even better idea would be to install a time-delay relay between the DC-300 and its controlled switched outlet from the main control center. The Amperite 115N050 with a 50-second delay and 5A capacity would do it.

The input impedance to the DC-300 is quite low compared with that of most power amplifiers. With the input level-sets (the front-panel knobs) half-way up, the input impedance is around 50k ohms, and this drops to 10k ohms with the controls up full. And since the amplifier's gain is about average, the controls will have to be all the way up unless you're driving highly efficient loudspeakers, so it is wise to check for compatibility with the preamplifier you plan to be using. Some will not function properly—they'll lose low end, among other things—with a power amplifier whose input impedance is less than 100k ohms, while others will match impedances as low as 10k ohms. Most solid-state preamp lifiers will work into 25k ohms or more, and have enough reserve gain and enough clean output to allow the DC-300'S input level-sets to be run at the appropriate position. The instruction manual, incidentally, shows curves for input impedance vs level-set adjustment.

Power
The most obvious question about the DC-300, though, is likely to be "Who could possibly need that much power?" Well, look at it this way: "Who needs high fidelity?" It just happens to sound better than low fidelity. And the DC-300 sounds bet ter than any lower-powered amplifier we have ever heard, even at very low listening levels. Whether or not the high cost of the DC-300 is worth the difference to you depends, first, on how your particular loudspeakers will respond to its ministrations (as mentioned above), and second, on how much any sonic improvement is worth to you personally.

Even apart from its sound, the DC-300 is built like the proverbial battleship, with the kind of attention to detail that makes all professional-type equipment seem so outrageously expensive until we find it still operating 20 years after the "competitively priced" audiophile equipment has succumbed to chronic parts disease.

Conclusion
Summing up, then, we would venture to say that this is the best power amplifier that is currently available, regardless of cost. We will even go so far as to guess that it will not be possible to build a better one, although we have some times been proven wrong on some similarly rash statements in the past. One thing we are quite certain of, though, is that this amplifier has spoiled us. After the DC-300, any other power amp will be anticlimactic. Unless, of course, someone can make one that sounds as good, is as well put together, and sells for $49.95. We won't hold our breath!—J. Gordon Holt

Manufacturer's Comment
The power output capabilities of past and present power amplifiers have been based, not on acoustic requirements, but on electro-economic considerations. Today's low-efficiency loudspeakers in a room of typical size would require several kilowatts of input power in order to produce (dissipation allowing) the greatest sound-pressure peaks that can occur in live musical performance. Clearly the larger the amplifier, other things being equal, the more faithful the sound. By delivering the maximum output power reasonably obtainable with today's semiconductor power technology, the DC-300 delivers a previously unattainable level of fidelity.

Since it is inevitable that a power amplifier smaller than several kilowatts will be overloaded from time to time when driving low-efficiency speakers at high volume, overload recovery must be instantaneous and free from subsequent thumps or distortion. The DC-300's totally DC-coupled design is unequalled in this respect.

Dynamically, the DC-300 is, as far as we know, without peer. Its ultra-low distortion required the development of an ultra-low-residual IM meter (less than 0.005%) to allow for actual measurement of distortion at levels down to 10 milliwatts output. (Harmonic analyzers are not sensitive enough.) The oommon practice of measuring IM down to no lower than 1 watt is not an adequate test for crossover notch distortion, as large amounts of IM are often produced between 10mW and 1W, while distortion above 1W is acceptably low. It is the DC-300'S extremely low distortion below 1W, plus its very low hum and noise, that make it sound so outstandingly good at low listening levels.

Incidentally, its noise is so low (typically 115dB below 150W into 8 ohms) that special voltmeters having a full-scale sensitivity of 100 microvolts had to be built in order to allow meaningful production-line testing of the amplifier.—Crown

Reviewer's Addendum
The DC-300 is quite capable of devastating most low-efficiency loudspeakers with its less-than-a-quarter-kilowatt of available power. May Heaven protect us, and our loudspeakers, from amplifiers of "several kilowatts" output!—J. Gordon Holt