Esoteric F-03A Integrated Amplifier

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Equipment report
Integrated amplifiers
Esoteric F-03A
Esoteric F-03A Integrated Amplifier

The comprehensive remote control fits nicely in the hand; it can also control Esoteric’s disc players.

The design and construction are lavish, as you’d expect in a $13,000 30Wpc integrated amplifier. The F-03A is a distillation of circuits created for Esoteric’s über-expensive Grandioso series, with a fully balanced preamplifier section, dual-mono construction, a switched-resistor attenuator (volume control), and the ball-bearing volume and source-selector knobs mentioned earlier. A fully balanced design requires double the circuitry in the preamp section, but results in lower noise and distortion. It also requires a four-element volume control (left +, left –, right +, right –). Rather than accept the noise and level imprecision of a potentiometer, Esoteric developed the Quad Volume Control Systems (QVCS), an attenuator built from switched-resistor networks. The volume knob controls an encoder that selects a combination of resistors from a resistor-ladder network to realize the precise amount of attenuation for all four signals. It’s vital in a balanced circuit that the + and – signal paths are identical in level, and QVCS assures that precision.

The output stage is a scaled-down version of that in the flagship Grandioso S series, with three pairs of the same output transistors as in the $40,000-per-pair Grandioso M1 (see Alan Taffel’s review of the Grandioso M1 in Issue 280). A beefy 940VA power transformer accounts for much of the F-03A’s 71-pound weight. The robust output stage, oversized transformer, and 40,000 microfarads of filter capacitance allow the F-03A to double its 30W 8-ohm rating when driving 4 ohms. An amplifier’s ability to double its output power when the impedance is halved has real-world performance benefits, particularly in reproducing music’s dynamics as well as delivering a solid, tight, and extended bottom end.

The casework and overall construction are no less impressive. Separate compartments within the thick aluminum chassis isolate subsections from each other and are arranged for the shortest signal paths. Custom multi-part machined feet isolate the F-03A from vibration.

For those who need more output power, Esoteric offers the F-05 at 120Wpc. I suspect that the $10,000 F-05 is identical in every way to the F-03A except that its output stage is biased to operate in Class AB rather than in Class A. The F-05 also lacks the F-03A’s drop-down door, and its isolation feet are less elaborate. (It turns out that the circuitry is indeed identical, but the transformer potting method is different between the F-03A and F-05.) The third model in the “F” integrated amplifier series is the F-07, which despite its higher model number, is the least expensive of the trio at $7500. It outputs 100Wpc, with cost saving realized by employing a smaller power supply, less thick faceplate, two-band tone controls rather than three, and a few other minor design features of the other two models.

As my “daily driver” for the past eight months, the F-03A was a joy to operate and to listen to. I chose the F-03A for review because I wanted an integrated amplifier that was musically satisfying as well as transparent enough to evaluate other products while I’m in my temporary scaled-down listening space. The F-03A fit the bill on all accounts. As I said at the start of this review, it would be a mistake to summarily dismiss the F-03A because of its modest power rating. Although it won’t deliver the ultimate in dynamics and bass extension with difficult-to-drive speakers, there are plenty of loudspeakers for which the F-03A’s output power will be sufficient. A speaker of 88dB sensitivity or greater should be a good match for the F-03A. When driving the 90dB-sensitive Monitor Audio Silver 300 or the 91dB-sensitive Piega Coax 711, the Esoteric never sounded strained. In fact, the bass was outstanding, with a wonderful combination of solidity in the lowermost octaves and excellent control and definition in the mid and upper bass. A good example is the track “Teen Town” from bassist Brian Bromberg’s album Jaco, a tribute album to his musical hero. The piece features Bromberg playing a bass line in the instrument’s lower register, and then overdubbing the lead line on the instrument’s highest register. The F-03A provided both the tonal foundation of the bass line with the pitch definition and articulation of the lead bass line. In addition to this solidity and weight, the Esoteric beautifully reproduced the texture of the bass along with its attacks and decays in a way that brought the instrument to life. The bottom end had real definition and expression, not just sounding like low frequencies. That’s my experience with speakers of average to highish sensitivity; I nonetheless recommend that you audition the F-03A with the loudspeakers you intend to drive with the F-03A before making a purchasing decision. I suspect that most listeners will be pleasantly surprised at just how dynamic and potent 30W can sound. Also keep the relationship between speaker sensitivity and amplifier power in mind: Every 3dB increase in speaker sensitivity is equivalent to doubling the amplifier power.

But the F-03A’s bass, though excellent, isn’t the F-03A’s raison d’être. This amplifier lives to deliver a sweetness and purity in the mids and treble that rivals that of very expensive Class AB powerhouse amps. There’s something about the sound of a pure Class A amplifier that is particularly beguiling. Class A in general, and the F-03A in particular, doesn’t sound like Class AB solid-state, but neither does it sound like tubes. The F-03A, like other Class A amplifiers I’ve heard, lacks the patina of transistor artificiality that overlays all but the very best (and massively expensive) Class AB amplifiers. This artificiality is manifested as a slightly dry, whitish, mechanical character in the midrange and treble that robs tone colors of their warmth and saturation. It’s this solid-state signature that turns many music lovers toward tubes. But Class A operation generally doesn’t seem to suffer from this affliction; instrumental textures are rich, full-bodied, densely saturated, velvety without being soft, and musically engaging. This isn’t to say that these qualities can’t be realized with Class AB operation, only that they seem to come easily to Class A (just the way bloom, air, and life come so easily to analog). The virtues of the F-03A’s Class A operation were readily apparent on a range of instruments, but were particularly salient on saxophone and vocals. The sax, with the most complex harmonic structure of any instrument (flute has the simplest, that is, the most like a sinewave), is revealing of any thinning or bleaching of tone color. I’ve enjoyed a lot of sax-featured music lately, from old classics such as Ben Webster’s Soulville (a great-sounding MQA remaster on Tidal) to Illinois Jacquet’s Swing’s the Thing (LP reissue), to contemporary masters of the instrument like Gary Meek (Originals) and Chris Potter (Amsterdam Blues). The F-03A’s smooth and suave upper midrange and lower treble beautifully conveyed a natural and unfatiguing tonality of this difficult to reproduce instrument. Similarly, the F-03A reproduced trumpets with a warm and burnished glow without the shrill edge that can mar the listening experience. Yet the Esoteric didn’t rob trumpet of its vibrant upper-midrange energy, soften its texture, or make it sound like a flugelhorn. All the life and energy were there without the steely glaze—a wonderful presentation.

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