December 2000Wavac Audio Lab MD-300B Amplifier
by Bill Cowen
Nuts and bolts
The MD-300B is housed in an attractive gold-colored chassis with a wooden faceplate and a taller medium-gray transformer cover to the rear. A heavy glass shield sits unfastened around the front of the tubes, and while open at the top, it offers a modicum of protection. Weighing in at an easily hefted 37 pounds, this amplifier does not follow the familiar path of brawn and mass. The chassis itself is fabricated of light-gauge metal, and while not flimsy by any means, it will not serve standby duty as a wheel chock.
On the front panel reside a large on/off push switch, a volume control, and an input selector. The tube complement consists of a pair of 300B output tubes, a pair of 6Y6s as driver tubes, and a pair of 12AT7s as input tubes. On the back, the speaker binding posts, three pairs of RCA input jacks, and an IEC connector for the mains connection complete the picture. Wait a minute -- an amplifier with a volume attenuator and multiple input capabilities is an integrated amplifier, right? Well, yes -- usually. And the MD-300B can most certainly be used in that fashion. But heres the thing: Its possible to connect the output of a preamplifier (active or passive) to one of the inputs, crank the volume pot up front to the fully open position, and bypass the "integrated" portion of the amp. Why would anyone want to do this? Wouldnt the sound quality improve with fewer connections and fewer components in the signal path? Well, again, yes -- usually. And in fact, with CD as the source, there was more resolution and a little added clarity when the MD-300B was used in standalone fashion. With LP as the source, however, I preferred inserting an active preamp into the signal path, as I couldnt get enough noise-free gain going directly into the amp. Obviously, my phono stage worked best with the additional gain of the outboard preamp. Yours may not.
Of interest, however, was that when doing sonic comparisons of the CD source with and without preamp, there wasnt a marked sonic penalty in the transparency and detail departments with the preamp involved. In fact, there was a little added bloom, a little extra gestalt, if you will, when the MD-300B was fed by the preamp. So little was the transparency penalty, and so nice was the extra beef to the music, that I spent most of the review period with the preamp in place. I wont mention the fact that my preamp has a remote volume control and that Im lazy as hell -- they have no real bearing on the issue. For those seeking the lowest cost of entry to the Wavac sound, however, the inclusion of the volume and switching capabilities provides a means of dispensing with the cost of a separate preamp. I could live quite happily with the MD-300B either way.
The principal design of this amp is the brainchild of the late Nobu Shishido, who developed a circuit he labeled the "IITC" (inverted interstage transformer coupled) and availed himself of the talents and manufacturing expertise of Wavac Audio Lab to produce his design. For the more technically challenged among us (like me), the IITC is more simply understood as this: a transformer is utilized between the driver tube and the output (300B) tube, replacing the capacitors that would normally be used for coupling that part of the circuit. Additionally, the first and second amplification stages are direct-coupled, rather than capacitor-coupled as in many other designs. Shishido felt that removal of these capacitors resulted in reduced coloration and distortion. Through further research, he found that only the highest-quality transformers were suitable for achieving the full sonic potential; thus, the transformers employed are critically selected and crucial to the overall sound of the amp. Sadly, Shishido passed away in 1998, but Yuzuro Ito, Wavacs chief engineer, carries on with Shishidos designs. The MD-300B is speced at 10Wpc, with a frequency response of 40-50kHz. I questioned Jim Ricketts of tmh audio (Wavacs US distributor) on the frequency response spec, and he said that Wavac is typically very conservative in their ratings.
To the sound
For the majority of the review period, the MD-300B powered the Coincident Total Eclipse loudspeakers. New to my equipment stable, the Total Eclipses are the big brothers to the Super Eclipses I reviewed last December. With a slightly higher sensitivity than the Supers, and sporting the same easy-to-drive impedance load, the Totals were a very nice match with the Wavac amp. Additionally, shortly after the amplifier arrived, a pair of Köchel K200 speakers found their way to my doorstep. tmh audio is the US distributor for Köchel as well as Wavac, so the K200s were added to my review slate along with the MD-300B. Youll see the review of these speakers on SoundStage! shortly, but in the interim, the K200s are a horn-loaded, very high-sensitivity speaker, and are a natural partner with low-powered amps.
I wont mince words here: The MD-300B is an enjoyable, refined, and wholly musical amplifier. Laying Clarence Carters "G-Spot" on the turntable, (from Have You Met Clarence Carter .Yet [Ichiban ICH-1141]), the most compelling quality of the MD-300B became immediately apparent -- bass and midbass lines that were quick, taut, and steered their way in and out of a transient with a litheness more commonly associated with solid-state amplifiers. I cant tell you that the IITC circuit was responsible for this, as I have no way of knowing what the amp would sound like without it. I can tell you that the speed and agility in the lower octaves were uncommonly good, and uncommon for most any SET design Ive heard. The extension was a little foreshortened, but not by much, and certainly not as much subjectively as the 40Hz low-frequency specification would imply. What was there was expertly articulated and had a good sense of weight.
The foundation laid by the bass lines accounts for another of the most endearing qualities of this amplifier: the superb pace and rhythm that set my foot tapping on every recording I played. If youre an analog aficionado, you know what I mean when I discuss the rhythm and pace that seem endemic to most British-built turntables. Thats what I kept thinking of when listening to this amp: rhythmic vitality, or a superb ability to present the full scale of dynamics with proper relationship, speed, and definition. This is not to suggest that other sonic parameters were left wanting, only that this particular trait stood out from the rest of the pack.
Up next was Phil Collins "Another Day In Paradise" (Phil Collins Hits [Atlantic 83139-2]). This recording can be a bit on the harsh side, and the Wavac MD-300B did nothing to mask it. It didnt make it worse by any means, but it spent no time sugar-coating it either. Do you want an amp that makes every recording sound good, or an amplifier that is true to the source? Ill opt for the latter, and the MD-300B served its role quite adeptly in that regard. An amplifier that arrives at a pleasant sound by masking resolution may be alluring at the outset, but quickly becomes boring and uninvolving. While not the most resolving amplifier Ive heard, the MD-300B strikes a nice balance between a faithful reproduction of all the notes, yet spares you from the hyper-detailed, sonic-spectacular kind of sound that I find as quickly tiring as the sound of an amplifier that sweetens things unnaturally.
"Hello Darkness," from Ric Ocaseks This Side of Paradise [Geffen 24098-2] is a piece that only brain-damaged hard rockers can enjoy. Maybe thats why I like it so much. More than anything, it revealed the dynamic capabilities from both micro and macro standpoints. Any amplifier that has the schwing must be good at the microdynamic thing by default, so as youve already read, the MD-300B has it. In spades. Macrodynamics were also good, but quite dependent on the speaker load presented to the amp. Here, I could get the Wavac to run out of steam on the Coincidents, but only at pretty high listening levels. Throw the Köchels in, however, and macrodynamics were of Memorex-commercial quality, even at stupid-loud levels. Do I have to say that speaker selection is critical when considering a low-powered SET amp? Good -- I thought not.
Dvoraks Slavonic Dances, as performed by the Czech Philharmonic Orchestra [Denon C37-7491] provided a nice window into the MD-300Bs ability to deal with string tone and complex harmonics. Strings came across quite nicely, with the proper amount of bite and rosin-on-string reproduction. Again, I noted some slight foreshortening of extension in bass lines, but only from a critical, reviewer-nerd-with pen-in-hand standpoint. Brass instruments were nicely defined, with excellent pitch definition and impressive dynamic contrasts. Overall, the MD-300B was excellent at doing what many SET amps do so well: reproduce the fine harmonic detail, structure, and natural development (and decay) of every note. This is where you hit the fork in the road between SETs and most solid-state amplifiers, in my experience. Where the Wavac breaks the mold, however, is in its ability to provide those special qualities without sweetening and/or adding euphonic colorations to the sound. I really hate to say it sounds more like real music because I know youre tired of hearing that old, worn-out phrase, but Im going to say it anyway. Sorry. And further, if the midrange is the home-field advantage of SETs, then Id have to say that the other team didnt even show up when the MD-300B hosted the game. The Wavac amp is so very enjoyable and natural in this regard that it clearly rises above most other SET amps Ive had experience with.
Los Lobos' "Kiko and the Lavender Moon," from Kiko [Warner Brothers 9 26786-2], was not only involving, I listened to it a half-dozen times, reveling in the clarity and see-through quality that is a fundamental strength of the MD-300B. The recording quality of this CD is quite good and provides depth and hall information that the Wavac amp portrayed accurately and convincingly. The soundstage was not super deep, but there was a very nice 3D rendering, and instruments retained proper relationship and proportion. Vocals were oh-so-nice, and while not to the point of revealing saliva molecules evaporating on the microphone diaphragm, the MD-300B got the essence of voice down pat. They say (whoever these "they" people are) that the best-sounding capacitor is no capacitor. If the elimination of the capacitors by the IITC circuit is any indication, Im going to have to meet "they" sometime and tell them they got it right.
Something about tubes .
As delivered to me for review, the MD-300B was outfitted with JJ/Tesla 300B output tubes. Western Electric 300Bs are available as an additional-cost option, and as I had a pair of well-broken-in WE tubes at my disposal (borrowed from my Cary 805C amps), I plugged em in to hear what the differences were. In short, the WE tubes propelled this amp from being merely great to really great. With the WE tubes, a new-and-improved level of transparency was laid bare before my ears. Minor nuances became much more intimately entwined with the fabric of the music, instead of a background artifact. Bass took on a new solidity and impact, lending a firmer foundation to the weight of orchestra and hard-driving rock. Most importantly, the WE tubes added to the rhythmic drive, which provided much greater involvement with whatever kind of music was plopped in the player. As you've read, the rhythmic mastery of this little amp stole my heart, and were it not for the WE tubes, my assessment in that area would not have been so overwhelmingly positive. The top octave was perhaps a touch softer -- maybe more polite, a little warmer -- but not to any distracting degree. Jim Ricketts voiced some surprise at my reaction with the WE tubes, as apparently his own experience had not been quite as positive. Perhaps listener bias and/or system synergy come into play here -- all I can say is that the WE tubes did it for me.
Lastly, the MD-300B performed flawlessly during the entire review period. For a tube design, it was exceedingly quiet. At idle, the only way I could hear any hiss or background noise was to stick my ear directly into the tweeter, and even then, the background hiss was barely perceptible. Left on for many, many hours at a time, the amp never got more than warm to the touch, and I never heard even one stray noise or amusical artifact emanate from it.
The only amplifiers on hand worthy of going head-to-head with the Wavac MD-300B were my mainstay Cary 805Cs. The 805Cs are priced at one-third more than the MD-300B, but they offer five times the output power (50 watts per side rather than 10). Sonically, the MD-300B showed its strength once again in the midbass, with the swiftness and cornering speed around notes like that of a thoroughbred racehorse. The 805Cs were more rounded in their presentation here -- enjoyable still, but not as quick. The 805Cs offered subjectively more extension in the bass, and had more weight, but the Wavac was addictive in its agility and delineation. While the MD-300B drove the Coincidents quite well -- surprisingly well, in fact -- the power reserves of the Cary amps gave them a notable advantage. Tonally, the Cary amps' presentation was more to the lusher, warmer side of life than that of the Wavac, which was a bit cooler and lacked some of the bloom. This is not a criticism of either amplifier, but merely a difference in presentation. The 805Cs tend to throw a bigger, more billowy soundstage -- the "whirlybird effect," as Carys chief guru Dennis Had likes to call it. In contrast, the Wavac does not offer up as large a soundstage, but renders more precise localization of performers and instruments within the soundfield.
Perhaps an analogy will do. The Cary amps are more like a big, leather-trimmed Autobahn-cruising Mercedes with mega horsepower on tap and a dozen cup holders placed in ergonomically strategic positions -- plush, comfortable, and sure-footed at any speed. The Wavac amp is more like a Porsche, capable of zipping through corners at breakneck speed, throwing out a fabulous exhaust tone, but focusing more on absolute performance than creature comforts.
While eschewing the battle-tank chassis construction of some amplifiers, the MD-300B is a well-built, solidly engineered product. With a pleasing tonal balance and superb rhythmic drive, it combines the appeal of the single-ended-triode sound with virtues that are not commonly associated with SET designs, especially in the bass and midbass. Yes, the output power is limited, so careful speaker matching is a requirement. But mate this amplifier with associated components of similar pedigree, and youre well on your way to the final audiophile resting place called sonic nirvana.
Review pieces come and go. Some cant leave too quickly, and some touch your heart in a way that makes parting very un-sweet sorrow. The MD-300B is one of the latter, and I will certainly miss it.
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