Solid State Preamp Reviews

My very first review of a preamplifier, for British magazine Hi-Fi News & Record Review in May 1984, was of the Audio Research SP-10. In my opening to that review, I wrote that, "more than any other component," a preamplifier "should approximate to the late Peter Walker's 'Straight Wire with Gain.'" By this I meant that a preamplifier should not be in the business of effecting dramatic changes, and in any case, dramatic changes are not the kind that prove to be of lasting value. However, I also wrote back then that what I became increasingly aware of while using the SP-10 "was the fact that 'neutrality' is a positive virtue rather than just an absence of aberration."

I still have that review sample of the SP-10, which I purchased following the review and used for many years. Since then, I have made the acquaintance of some preamplifiers that are even more neutral than the positively neutral SP-10. But in the years since the publication of that review, I have also become increasingly aware of the paradox that while loudspeakers in general have more character than preamplifiers, I can accommodate to a loudspeaker's sonic signature far more easily than I can to a preamplifier's.

So even though I've been content with my long-term preamplifier reference, a decade-old Mark Levinson No.380S, I've kept a corner of my eye open for a possible successor. I had been impressed with Parasound's Halo JC 1 monoblock, which I had measured for Michael Fremer's review in the February 2003 Stereophile (Vol.26 No.2). And I'd had enormous respect for the Halo JC 1's designer, John Curl, ever since the early 1990s, when I'd used and enjoyed one of his Vendetta SCP-2 phono preamplifiers. So when Parasound prexy Richard Schram e-mailed me, after last year's Home Entertainment Show, to ask if he could drop round with a sample of his new, Curl-designed Halo JC 2 line preamplifier, he didn't need to twist my arm too much.

The Halo JC 2
Costing a not-unreasonable $4000, the Halo JC 2 is manufactured, like the JC 1, in Taiwan. But its design, circuit layout, and parts choice are unabashedly American. John Curl began designing the JC 2 while working on the JC 1, and optimization of the design was performed by him, with the late Bob Crump choosing the parts and Carl Thompson laying out the boards. "Designed by CTC Builders John Curl, Carl Thompson & Bob Crump," it states at the top of the rear panel—a nice touch.

Styled to match the JC 1 and finished in the same brushed, natural aluminum, the JC 2 is a smart if rather bulky-looking component. The front panel is dominated by a rectangular red logo at the top center that glows bright red when the amp is operated, and by a volume knob at the far right. An inset panel at the bottom contains an aluminum pushbutton at each end, these softly backlit in blue; between them runs a row of six blue LEDs, to indicate which source has been selected. The source-selector button is the one on the right; pushing it repeatedly scrolls through the inputs from left to right. The button on the left wakes the preamp from Standby. A red LED flashes when the preamp is muted with the remote. There is no balance control as such, but two small knobs adjust the two channel gains by up to –10dB.

The rear panel is dominated by the two rows of input and output jacks, one row for each channel. There are six pairs of unbalanced inputs, two of which can be switched to balanced mode. As well as a pair of fixed-level Record Out RCAs, there are inverting and non-inverting main unbalanced outputs on RCAs and a pair of balanced outputs on XLRs, these wired with pin 2 hot. The gold-plated RCA jacks are all sourced from Vampire, the XLRs from Neutrik.

Internally, vertical 3/8"-thick aluminum panels separate the chassis into three shielded regions. On the left is the inductor-smoothed power supply, based on an R-core transformer and fast, soft-recovery bridge rectifiers and diodes. There is a separate supply for the relay coils, triggers, LEDs, and control circuitry, this carried on a vertical board behind the front panel.

The audio circuitry, shielded from the power supply and control sections, is carried on a separate board for each channel, and is based on hand-matched complementary FETs, a feature of John Curl's designs for a quarter-century now. The circuit is direct-coupled, with no capacitors in the signal path, and with DC offset controlled by a servo circuit. Following the short signal path, the input jacks feed a relay driven by the input-select switch. A four-gang, motor-driven potentiometer adjusts volume and polarity inversion of the output signal is performed with gold-on-silver–contact relays.

The Halo JC 2's construction is to a high standard. The only disappointment was its rather flimsy and resonant top plate and its plastic remote.

Sound
I have never been one to believe in long break-in periods—or even break-in, period, for anything other than loudspeakers. But to my surprise, the Halo JC 2 definitely improved in sound quality during the first week it was plugged in. Not that this Parasound will ever be mistaken for a mellow-balanced component, but it took a few days of being left on for the initial brashness of its mid-treble to slowly recede until it was properly balanced with the midrange and top octave. Then I began to appreciate how much it did right and how little it did wrong.

Take soundstaging. Many audiophiles dismiss the ability of a component to render a believable soundstage as being a superficial indicator of its quality. But ever since I first heard a system that could paint a stable, accurate, solid picture of the recorded event, I have placed a high value on this aspect of sound reproduction—as long as it is not achieved at the expense of similarly great performance elsewhere.

Kal Rubinson recently gave me a copy of Marianne Thorsen's performance of the Mozart Violin Concertos 3–5, with Oyvind Grimse conducting the Trondheime Solistene (SACD, 2L 2L38SACD), which he listed as one of his "Records To Die For" in the February issue. Recorded in a small church, the sound is quite close, but the Halo JC 2's ability to resolve spatial information allowed me to detect the subtle dome of ambience surrounding the musicians, especially in Thorsen's unaccompanied cadenza in the Adagio of Concerto 3. The balance was somewhat light in weight, but there was enough lower-midrange energy to flesh out the delicate scoring.

Compared with my long-term reference preamp, the Mark Levinson No.380S—also a soundstaging champ—the JC 2's lighter balance allowed more of the recorded detail to be resolved without thrusting it forward at me. On the 96kHz-sampled version of Neil Young's Chrome Dreams II (DVD/CD twofer package, Reprise 340220-2), the Parasound's superb definition on the drums and bass guitar was highlighted by the hints of the recording studio acoustic illuminated by the drums. The hushed, luminous backwash of strings that presages the entrance of Hilary Hahn's solo violin in Vaughan Williams' The Lark Ascending (SACD, Deutsche Grammophon 28947-48732-6) was spread from far left to far right, yet the central image of Hahn's violin remained small and vulnerable, stable, and free from bloat.

During the review period, I was working on the remastering of Stereophile's latest CD release, a reissue of Robert Silverman performing the two Rachmaninoff piano sonatas (STPH019-2). When I played the 16-bit WAV master files from my Slim Devices Transporter, the transparency of the JC 2 allowed me to hear slight low-level glitches that I needed to clean up in the mastering. But to my surprise, I heard a very slight improvement in the sound's tangibility when my WiFi network was down for a while for updating and I used a hardwired Ethernet connection from my Mac mini to the Transporter. But I shall say no more—that way lies madness.

The Halo JC 2's ability to reproduce space was even evident on monophonic recordings. I bought the reissue of Miles in Berlin, the first live recording of the great 1960s Miles Davis quintet (CD, Columbia/Legacy 2796-93594-2), back when it was released in 2005. But I hadn't played it much, both because it was mono and because I found off-putting the breakneck tempo with which bass player Ron Carter begins "So What." But giving the disc a second chance one night when I had the Magico V3 loudspeakers set up with the JC 2 and JC 1s, I was surprised to be able to hear deep into the mono image, the instruments sufficiently separated in space that I could now start to make sense of the music-making during this tune, and begin to comprehend the interplay of Carter, drummer Tony Williams, and pianist Herbie Hancock. In "Stella by Starlight," I could hear Miles backing away from the mike during his solo to emphasize the dynamics, and tenor-sax player Wayne Shorter approaching the mike to take his solo in the same song.

Yes, the Parasound could do space. But the first aspect of the Halo JC 2 that I noticed was the definition and the weight of its low frequencies. It grabbed my attention when I was finishing up my review of the KEF Reference 207/2 loudspeaker (February 2008), and the battery of my iPod had given up just as I was leaving the office for the night. "Borrow mine," said Stephen Mejias—a generous gesture, considering that listening to someone else's iPod is like listening into his soul.