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To properly match JE Audio's monos on power and—admittedly secondarily and less successfully—on price, my new €15.000,- Boenicke B10 speakers became the chosen transducers. At 87dB efficient (10" sidefiring Neodymium-powered and series-connected sealed woofers without low-pass filter; paralleled 4" flat-diaphragm mid/tweeters with single cap @ 1.5kHz/6dB/octave) this deceptively compact and very attractive 4-driver 2-way seems to thrive on low-impedance power. For this load my in-house transistor amp of choice is Dan Wright's overachieving ModWright KWA-100SE.
For tubular comparisons I had my beefy Octave 130-watt 4 x 6550 monos; and Trafomatic Audio's 30-watt Kaivalya 4 x EL84 monos with interstage transformer coupling. How would John Lam's balanced VM60 design distinguish itself against the 2-stage transistor amp and push/pull valves?
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27" iMac, PureMusic 1.82, Esoteric C-03, Octave MRE-130, Trafomatic Kaivalya, JE Audio VM60, ModWright KWA-100SE
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None of the tube amps matched the Mosfets on LF control. Where the transistors cut a straight swath into the abyss, all of the glass bottles introduced a modicum of looseness and bloat most noticeable in the first octave and lower half of the second. On delta of difference the Octave monos were closest to the transistor reference. The Serb and Hong Kong monos joined for third place. The higher output impedance of the transformer-coupled tube amps quite literally reflected on their ultimate ability to control two series-connected 10-inch woofers loaded into a very compact sealed enclosure. Whether you call it bloomier or boomier reflects your sympathies but it's the same phenomenon. |
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When I reference tone density, the easiest visual are bunches of hard smooth dimpled golf balls versus minorly furry tennis balls. They all represent individual sounds. Expected tubular action is growing tiny hairs. That surface fuzz adds textures and subjective size; render outlines softer, transitions more watercolour and intermingling; and in the process creates connective tissue. Most tubes play tennis. Transistors play golf. With transistors there's finer separation. There's higher transparency down into minutiae. Simultaneously something else strips back and flattens/thins out a bit. Walking the fine line between these two actions is a core concern of mature listeners who've explored the highways and byways of this hobby with the various flavors and their excesses.
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| Exhausted by the limitations of excess, they now desire to walk the middle path. That's not necessarily the same as dead neutral. It's simply close enough to suit a personal musical diet while exploiting variability—different recordings should sound more rather than less different—and enjoying the desired balance between tonal heaviness and image density versus transient speed, separation and transparency. The first thing to be said on this count is that all of these amps were close enough. At this level excessive deviations no longer occur. Yet differences remain. Here the drier more incisive Kaivalyas played it more transistorized than the bigger pentodes. |
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Between Octave and JE amplifiers the primary difference came down to a cooler tint backed by greater ballsiness and shove for the Germans; and a warmer softer mien with less slam but greater microdynamic agility for the Asians. John Lam's circuit exhibited small-detail resolution very close to the transistors but added tonal weight - what valve slang usually calls saturation to indicate that color temperatures seem deeper. The B10 speakers' low-ish voltage efficiency means they don't kick in as fully at very low levels as for example the just reviewed 97dB Rethm Maarga. Here the VM60 action of injecting a strategic amount of heaviness became a welcome asset. It filled out the Boenickes prior to their own complete 'arrival' on the SPL meter. |
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| On complex and highly dynamic fare like Juan Carmona's Sinfonia Flamenca the ModWright amp demonstrated the greatest unflappability. Leaner and drier like the Kaivalyas but endowed with clearly greater current drive, it maintained the highest degree of intelligibility and best bass. On mellower melodic fare like the slow numbers on Lila Downs' Pecados y Milagros [Sins & Miracles] the VM60s ruled with highest vocal expressiveness and intimacy. None of these amps were as lucid and lit-up whilst simultaneously as resolved and refined in the treble as the wide bandwidth Nelson Pass SIT2. Yet the latter's 10-watt power into the Boenicke speakers wasn't ideal. Achievable levels were plenty, driver control particularly in the lower octaves was sub optimal. |
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Returning to John Lam's monos presented an obvious but ultimately preferable trade-off. While magnification power stepped down a notch, timbre heft went up. This increased what I call incarnation factor. That's the difference between more ghostlike electrostaticity and greater dynamic in-room presence. Given the VM60s' showing of essentially standing in for the €10.000/pr Octave monos—being not identical twins but clear equals and very similar—their $6.100/pr sticker became a very important happy qualifier and the most exciting bit of this assignment.
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Though officially rated at half the output of the Germans, the JE Audio monos in my 5.5 x 12m space
and into a true full-range but conventionally inefficient speaker were plenty butch. It suggests that equivalent B&W, Dynaudio or Sonus Faber models would be just as well served. In ultimate terms which specifically consider sheer grip on associated woofers, the minor question mark remaining is complete bass control. That'll depend on the given interface and what yard stick one applies. It'll be the very rare valve amp after all that'd survive an encounter with Gryphon or Boulder transistors on the merits of being boss on low frequencies. This game is still about minor compromises and priorities.
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Conclusion. The JE Audio VM60 monos exhibited typical push/pull tube virtues of superb lateral soundstaging vs. less depth perspective than the best single-endeds. This was accompanied by greater macrodynamic fortitude than microdynamic gradations. Then John Lam's monos quite downplayed the breed's often inherent congealing effect which I view as the common price to pay for greater tonal robustness and image density. (Think of lights dimming a bit while everything gets pumped up some and more crowded). Without the inward-illuminated effect of a 45 triode, the VM60s showed finely nuanced treble and added expected valve textures which were administered carefully to not sacrifice much magnification power in trade. The higher-than-normal resolution for this component category and price class probably tied to the balanced circuit's greater precision than the usual phase splitters.*
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* In fairness here we must question which preceding component generates the balanced signal and just how it goes about it. In practice JE Audio simply shifts the burden of balanced-signal execution on the maker of your preamp or source component (whichever sports the necessary balanced outputs). This does not eliminate possible compromises. If your preamp for example lacks true balanced circuitry and merely has convenience XLRs, you should inspect whether the better results really come from using those than entering the VM60s single-ended.
Though it could seem damnation by faint praise—grosser deviations from the middle simply read more colorful—the VM60 monaural amps were admirably 'close enough' to neutrality to not leave a readily recognizable finger print on the proceedings. Yet they performed minor body work that telegraphed not as real warmth and more as tonal heaviness compared to standard transistors. This avoidance of warmth was likely because of a low noise floor which I ascertained with 100dB speakers. This reconfirmed higher than average resolution for this type of device. Add a sell price that proved competitive with gear priced 40% higher and JE Audio's revised monos turned out to be a very solid highly mature and also cost-effective entry in the ambitious upper mid-power tube amp sector where owners refuse to have their speaker choices dictated by the amplifiers. |
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Manufacturer's comments: It's a great pleasure to read Srajan's review of our VM60 power amplifier. The review brought up an interesting question about balanced (XLR) and unbalanced (RCA) signals feeding a power amplifier. From an audio designer's point of view, I regard it as the responsibility of the source component or preamplifier to generate the balanced and unbalanced signals. A power amplifier's job is to amplify any given signal in the best possible way and with sufficient current to drive the loudspeakers. It shouldn't be the power amplifier's job to create a balanced signal or to convert an unbalanced signal into a balanced one. In conventional push-pull vacuum tube power amplifiers there must be a phase splitter to create two out-of-phase signals .Unfortunately the sound quality is greatly influenced by this phase splitter.
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balanced power amplifier has the potential of reproducing better sound. However we should not take for granted that it always will sound better. Some so-called balanced amplifiers use an input transformer or op-amp to convert an unbalanced signal. Or the internal power amplifier electronics are an unbalanced design that cannot support balanced signals. Such amplifiers will not benefit too much from a balanced source. A true balanced power amplifier should take balanced signals directly. The internal electronics will be a fully balanced circuit that supports both positive (in-phase) and negative (inverted) signals. At the output the loudspeaker connects only to the positive and negative terminals not any ground. Power amplifiers produced by JE Audio are true balanced power amplifiers. As a result our amplifiers will sound better with balanced than unbalanced signal sources.
John Lam
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