Tube Power Amp Reviews

Much has been made of in some quarters of the poor linearity of SE tube designs at high levels. My experience suggest that if good linearity can be achieved with good components, tubes, and transformers operated in their mutually optimized working regions, then such an amplifier can actually have satisfactory distortion at peak levels. In fact, the distortion is comparable with that produced by many loudspeakers at the same power level. And at lower levels, where both speaker and the listener's ear exhibit rather less distortion, the performance of this type of amplifier continues to improve. In fact, distortion can be substantially good at moderate power levels, and improve to virtual perfection at still lower levels.

Its power-supply design also distinguishes the 300SE from lower-cost tube designs. This monoblock enjoys the benefits of a heavy-duty, full-wave tube rectifier whose inherently low feedback capacitance and freedom from reverse recovery transients result in very little spurious signal energy, thus making for lower noise on the power rail. The 590V primary supply serves all the tubes. The series-connected pair of 1200µF reservoir capacitors are fed via a choke filter, while a second cascaded-choke "pi" filter serves the input stage with power of very low noise. There are also DC supplies for the tube heaters.

The 300SE LX20 is hard-wired throughout. There are no printed circuits, and a proper central "star" ground is established at the power reservoir. Wiring is single-strand silverplate, self-supporting and Teflon-insulated. The input cabling is pure silver. In addition to that special oil-filled metal-foil capacitor—the only coupling component in the signal path aside from the output transformer—there are also a number of top-quality polypropylene film capacitors, these used for higher-frequency supply and bypass.

As if all this were not enough, Cary has commissioned a still better, optional output tube from Kron for the LX20 series, at a premium of $100 per channel. The T100 tube has some mechanical reinforcements, while its electrodes are made of titanium, said to give an even better sound. I tried both versions, but found no significant differences in biasing or test-bench results, save in respect of decay resonance.

Sound
Despite a well-remembered and happy musical experience with Cary's CAD-572SE monoblocks, as Cary's new 300SE LX20 it firmly established its superiority over the 572SE as it broke in. I was impressed by the 300SE LX20's convincing quality of music replay. From the first note, the amplifier had that uncanny, even spine-tingling ability to convey the innate "startle factor" of really clean transients—the very reason for their presence in music. The 300SE LX20 was shocking in its ability to deliver impact, to surprise and startle, and for the revelation that so much of the drama, excitement, and impact of reproduced music is flattened and compressed by so many other power amplifiers. Within its compass, reasonably and sensibly matched to a fine loudspeaker, the 300SE LX20 proved a veritable cracker for pace, rhythm, and timing—never mind lively dynamics.

And what a bundle of energy it was! Lively rock and dance material was positively blasted across the acoustic interface to the listeners. Track after track was delivered with consummate panache. Lively, explosive, punchy, coherent, gutsy, macro- and microdynamic, focused, precise, revealing, involving—all of those adjectives sprang to mind. This sound really lifts the spirits, matching an exemplary degree of involvement with a generous, broad, "300B" tonality and wholly believable timbres.

Fine detail was well resolved, and nothing seemed missing, even at the frequency extremes. Even in the context of classic hi-fi virtues—image depth, focus, bandwidth, overall control—this amplifier sounded very competent indeed.

It came a remarkably close second to Cary's astonishing CAD-805C in terms of dynamic power. I achieved a more than satisfying loudness with my Wilson WITT II speakers (89dBW/8 ohm load) with this amplifier in a reasonably large room (8822ft³). Of course, you'd hope this would be true, given the $4000/pair difference in price.

You probably won't impress your friends with how much bang you get for your buck with this amplifier. Rather, it's its high quality and revealing musical insight that they'll come to appreciate. But if you sit closer to the speakers than I did (12') and in a smaller room, the available power should suffice for any reasonable loudness demand. And at normal cruising levels it felt totally unstrained, exhibiting a grip and a satisfying dynamic authority generally associated with more powerful amplifiers. The Cary was so relaxed in its delivery that levels of aural fatigue were very low; I could listen for hours on end.

When an audio system fails to rock well enough, and is uninvolving when playing back pop recordings, I'm driven to find solace in classical music, which is often more episodic and thus less demanding of good rhythmic exposition. So striking was the Cary's transient and rhythmic performance that it dug deep into all kinds of recorded music, and to such a degree that many familiar classical recordings that I commonly use were now heard with hitherto unsuspected degrees of rhythmic drive.

The Leonard Slatkin/St. Louis Symphony recording of Mahler's Symphony 2 (Telarc CD-80081) is almost too naturally balanced for its own good. On most hi-fi systems this CD sounds rather distant and sweet—in my view, row 20 or 30 rather than the usual 5. Unless your system is unusually lively and transparent, this CD can prove underwhelming.

Not so with the Cary in the driver's seat. This mellifluous power amp somehow reached into this recording's inner balance, its usually understated naturalness and harmony. In some respects, this was exceptionally rewarding. For the first time I became mysteriously aware of Slatkin's presence as he led the ensemble, maintaining the flow, always there to remind musicians of those details worked in rehearsal, and building a fine musical edifice. I could really sense the presence of the man driving the performance. The orchestral playing sounded more exciting, expressive, and dynamic, and better structured.

As if this weren't enough, the 300SE LX20 also fared very well on tone color. String tone was more believable, more coherent, while different string instruments were clearly differentiated by size and character, and not merely by the range of pitches they could reproduce. Likewise, woodwinds sounded natural, airy, and free from hardness or "screech"; the 300SE LX20 was revealing of instrumental tone color, and of how each instrument was played.

There is almost no need to go on—the amplifier simply did a really fine job of transmitting the best elements of the musical picture, somehow ameliorating the effects of many amusical artifacts of the reproduction process that can detract from the overall effect. Amplifiers such as these also teach us just how many of those unwanted aspects—emphases, false sounds, masking, etc.—are present in so many other amplifiers.

In the early stages of my evaluation, it was hard not to be drawn to the excellent timing, the ability of the 300SE LX20 to clearly elucidate the start and finish of a note, and of the vital time intervals between notes. Where many amplifiers can sound slow, loose, even uncommitted, the Cary was positively locked in, tautly synchronized with that elusive inner pulse present in all good performances and recordings. This was particularly true with the T100 output tube. Some greater transparency and spaciousness were also present with this choice.

Stereo imaging was exemplary. Stage width was very good, with no false noises on- or offstage, no "splashing" of image information to defocus the effect. Over the primary stage, focus was excellent—strikingly better than the norm, and the more so for its most obvious coherence. By this I mean the proper and natural association of diverse higher-frequency harmonics with their lower-range fundamental components. High-treble "edges" were not, in this case, disassociated from the dynamic "attack" components of midrange sounds. Indeed, as a result, treble focus was exceptionally good.

To this highly focused picture I can add equally exceptional depth. Achieved without emphasis, the outstanding level of transparency helped to deliver soundstage resolution that reached way back, clearly illuminating the far boundaries of the recorded acoustic, convincingly delineating the placements of performers within this large acoustic, and placing natural "air" around the performers without false brightness—indeed, it sounded more like an aura or "glow" than the oft-encountered pseudo-"glare."

Thinking in more depth about the subjective frequency response, the 300SE LX20 was not perfectly neutral. However, there were two sides to this. In respect of what I might call its "inner" neutrality, the LX20 must be about as good as you can get. Encompassed in this are those imbalances that can be called amplifier colorations: grain, tizz, roughness, glare, hardening, and boom. These were notably absent from the LX20's sound. The Cary sounded warm compared to the average solid-state design, but its treble was not dim or dull. In fact, transients were excitingly clean and crisp—what was missing was any trace of a grainy or hard overlay or emphasis.

The Cary's departure from neutrality was significantly less harmful to the music than the usual amplifier colorations noted above. The audible error very probably arose as a consequence of the finite and significant output impedance. Unless your speaker has a flat impedance curve, the effect of significant source/output impedance from any kind of amplifier is to mildly alter the response of the speaker it's used with. This interaction is often audible, and will vary in severity according to the nature of the impedance of the speaker. The effect is quite small with the Wilson WITT II, for example, especially on the amplifier's 4 ohm setting—just some additional upper-mid presence and some mild lift in the midbass.

While the LX20's midrange has convincing percussive qualities, I also found that the bass possessed a convincing kicking "bounce," and was articulate and very tuneful—indeed, as if the high resolution so apparent in the midrange was continued directly down into the bass. With a number of other SE tubed amplifiers, the bass can sound significantly softened and uneven. Interestingly, the Cary CAD 300SE LX20 was so punchy and dynamic that while the bass sound was still a little different from true neutrality, it didn't seem to significantly lack evenness or extension. Nevertheless, I would expect some speaker dependency in this matter.

I tried the Cary with the Quad ESL-63 speakers and found the combination truly mellifluous. The Quads made no difficult demands of the Cary, while the acknowledged tonal purity of these electrostatic speakers was transported to a new dimension by the LX20's zero-feedback design. At moderate levels, and in context, a BBC LS3/5a Mk.I showed near-magical presence and resolution. Likewise, I got a most synergistic system match with Spendor's promising new box, the SP3/1P. This Epos ES11/12-sized speaker has usefully high sensitivity and an easy 8 ohm loading—right up an SET's street.

Conclusions
Assuming that issues of sufficient power and load matching are under fair control, this amplifier stands with the world's finest. While it lacked the final clout of the Cary 805C, it fought back with truly exceptional liquidity, transparency, focus, and purity of harmonic line. In provided new definitions for upper-frequency sparkle, air, shimmering ambience, lightning-fast transients, and highly resolved microdynamics. Moreover, within their limits, the bass, mid, and treble are all very good. For what it does so well, I just have to give the 300SE LX20 a subjective quality score of 50 points on my personal scale.

Much as I value and could not do without the towering all-around performance—any level, any load, any power—of the solid-state Krell FPB 650M, I also find that I can't do without the services of the Cary 300B LX20. It deserves a medal all its own, for services in the cause of natural music reproduction! I cannot forget its natural harmonic line, the liquid textures, the sense of air and space, the transparency, and the fine perspectives. Likewise, I must include the drama, rhythm, dynamic expression, and strong listener involvement, achieved with a very low fatigue index.

So while it isn't the biggest amplifier around, and requires intelligent use and a carefully matched system, the Cary 300B LX20 can create natural musical experiences that are very hard to match. In the Super Amp stakes, this one shines brightly—yet in context, its price is essentially realistic, and honestly reflects Cary's purist engineering. The Cary 300SE LX20 defines much of what Class A performance must be about—even, or perhaps especially, at natural sound levels.