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| "The Neo's output transformer is indeed a pivotal component in the overall signal flow, and is one of about a half dozen quality-sensitive 'make-or-break' components in the amplifier. Interestingly, this design had its beginnings in a friendly but competitive argument between rival designers [David Manley and Peter Qvortrup, Ed.]. Here, plaintiffs protested loudly that a satisfactory, never mind sonically attractive, switchable SE-PP amplifier would be impossible to design and produce. The defendants countered by vigorously insisting otherwise. The actual answer turns out to be that the arguing parties were simultaneously wrong and right! The key lay in the juggling of many different amplifier design parameters, most of which were related to the output transformer. | |||||||||||||
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However, many of the transformer parameters remained unassailable, hence unchangeable except in a sonically positive direction - such as minimum primary inductance for example, Any revision of the output transformer's characteristics that would reduce bandwidth, raise distortion, raise the noise floor, or otherwise impair performance was deemed a price too high to pay for this application. Curiously, however, the main transformer parameter widely adjustable without excessive sonic penalty was the transformer's efficiency. In this case, perhaps 7 to 9% of the signal developed by the set of 300B output tubes would be lost in the conversion from the high plate impedance primary side to the low secondary impedance loudspeaker side, depending on the mode selected. This as compared to, for example, 2 to 5% for a typical fixed-topology push-pull output transformer. Trading the loss of 1 - 1.5dB of output power in each mode for good bandwidth in both modes was the way to go! Better to have an imperceptible reduction in maximum output power than to intentionally configure the amp's sonic performance in such a way that one mode's sonic qualities would tower over the other, or have to settle for mediocre sonics in both modes in order to prove a point. If it cannot be good in both modes, then it is best not done! With the output transformer's design foundation in place, time and effort was spent evaluating core material choices, refining the core winding interleave, and extending the bandwidth. Particular attention was paid to the lamination stacking and core gap arrangements, along with the choice of insulating materials used throughout the assembly. By doing so, the finished output transformer was made able to transmit satisfying amounts of bass in both SE and PP modes -- something unique in the industry -- along with good midrange bloom and a very sweet and seductive top end. |
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In addition, the transformer's reasonable bandwidth and easy interaction with the output stage -- which is already a pair of forgiving triodes -- meant that the amp could safely be offered with adjustable negative feedback. The stepped negative feedback control ranges from the exotic setting of 0 dB, up to a buttoned-down 10 dB, and include all of the remarkable and diverse tonal shifts that go along with such arrangements. One must start with good linearity and bandwidth to offer 0 dB of feedback in a transformer-coupled design. Now the remaining interesting and subtle sonic differences one hears when comparing the SE and PP modes are due primarily (no pun intended) to the changes in amplifier driver and output stage topology, rather than being dominated by electronically induced shifts or compromises of the output transformer's behavior..." Time to take Neo for a ride and form my own opinions. From first power-up, these amps reminded me of the Moto Guzzi 850 El Dorado civilian police bike I used to own. With its transverse V-twin dating back to the firm's WWII tractor engine, everything about that bike -- for a while the ride of choice of California's Highway patrol -- was solidly yeoman, ultra-dependable yet clunky, with switches, starter and gearing harking back to that reassuringly industrial-strength tractor DNA. My subsequent BMW Paris-Dakar Enduro was slicker in many ways though it shared with the goose legendary ruggedness and do-thing-yer-own-way cosmetics (Teutonic stubbornness vs Italian charm?). But the German machine lacked the Italian's peculiar appeal of mechanical substance and throaty rumble. |
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| Turning on the Neo monos created a mild, completely non-alarming surge of power supply noise -- presumably while the capacitors where charging up -- that would always extinguish after just a few seconds to leave the operational amps dead-quiet over my 103dB horns, except for some mild tweeter hiss audible only from a foot away (normal even for transistor amps) but truly mute on the midrange horn. Impressive. However, switching from SE to PP operation even with the mute toggle engaged caused a massive transient 'thonk' each and every time, likely being less obnoxious with less efficient speakers but quite brutal on my Avantgardes. Think Moto Guzzi gearbox - clunky, as though tripping a massive lever in some complex machinery. I reassured myself that the speakers weren't the worse for the whacking bit but, in all bluntness, didn't care one iota for this kind of regular shock treatment regardless of its ultimately non-lethal nature. Throaty rumbles and thumps, after all, are part of classic motorcycles but not fine audio playback devices. | |||||||||||||
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That said, the Manley monos behaved gentlemanly in all other ways. Considering the awesome flexibility of 44 variations on a musical theme (2 modes of operation x 11 feedback modes x 2 output impedance settings), their klutzy transition might be forgiven. What is less tolerable if your assumptions of 300B amps included dainty notions of he-loves-me, he-loves-me-not romantic insecurities? An ultra-dynamic, hard-hittin' and utterly ballsy way with rim shots, bass transients and angular funk like the Neville Brother's "Angola Bound" on Aaron's Warm your Heart [AM Records, 75021 5354-2]. Wall flower be gone. Instead, think Russell Crowe's master & commander Jack Aubrey. Upon having physician friend Stephen Maturin offering to name a biological discovery after him, he retorts with a manly "Make it a plant - bristly and ineradicable." |
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| That's the NeoClassic 300B in 2dB feedback, single-ended guise - ineradicable by even the meanest, nastiest of music, bristly in the face of formidable foes. Okay, I didn't have misogynist thug Rap to throw at it, but Techno and EW&F funk didn't upset these monos one wit. Lest you think the Neos acted all ornery brutes without finesse, we'll delve into the string quartets and breathy Jazz vocalists in a moment. But little good is gentleness and refinement when a component lacks timing, incision and fortitude to handle especially midbass and upper bass transients where most the musical gumption lives. And while, indeed, the Neos weren't the last word in thermionic romance, they grabbed a hold of rhythm and attacks that was invigorating, spunky and lively as hell. So before we go all audiophile and listen to Jacintha -- just kidding -- let's consider real music first. Needless to say, 12/24 watts will only get you so far. They require copasetic loads to not act malnourished and short of breath. But obey intrinsic reason and you'll find that these Manleys are not your archetypal 300B pansies. That observation also includes notable absence of dense harmonic distortion. Don't go NeoClassical if you're a saturation hound that howls contentedly at midrangey excesses. Despite their backlit fascias whose interior lamps spill further light through the lateral and bottom slots, these Manleys are far more honest and less indulgent, hence closer to the 300B KR Audio Antares aesthetic than Cary's SET ideal. |
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| Some of the Neo's wallop factor stems from a minor midbass emphasis which doesn't turn gelatinous but adds body in the right place and cracks like a whip when the occasion warrants. Musically speaking, the higher feedback settings proved useless - the magic lived in the 0-4 range, with NFB increased outside this window flattening soundstage dimensionality and wet-blanketing the musical energy. I'm reminded again of Mesa's Randy Smith who, upon digesting John Atkinson's test bench results for the Baron's feature review, groveled with bitterness that he should have included a 'test bench' control. By virtue of massive amounts of feedback, that would have made the Baron measure like a flat-lined but respectable corpse. It also would have sounded dead as a stiff, he'd add with a smirk, but then what did the bloody measurement jockeys expect? |
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Single-ended Neo bass firmed up with a few degrees of correction but, on baroque or simple acoustic fare, sounded most fetching in 0dB mode. P/P had more bite and edge definition to prove addictive with snarling brass and raucous percussion workouts while vocals always sounded more present and convincing in SE mode. Large-scale orchestral acquired more mass and soundstage width in P/P yet remained more intelligible, transparent and 'on the breath' in SE. While the treble was likely more extended and honest in higher-power guise, high end's pellucidness sans phase splitter was not to be denied. It eventually made me settle down with SE and 2dB of NFB. And while certain tracks would have benefitted, in specific areas, from absconding with my initials and returning to push/pull's greater slammatronics, I frankly couldn't be bothered to tune these amps from track to track or CD to CD. Mind you, to the right personality, this completely fluid demeanor of the Manleys could well be ultimate entertainment and anti-boredom therapy. You'd annotate your entire software collection with preferred settings and be scientifically audiophile about the whole thing. |
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