Parasound Halo JC 1
Monoblock Amplifier
High value at a low(ish) price! 

Review By Wayne Donnelly
Click here to e-mail reviewer.

  The reader may be somewhat surprised at finding a Parasound product reviewed in Superior Audio. This San Francisco-based company has for years offered well made, good-value products that compete principally with other value-priced marques such as Adcom, B&K and Rotel. Since 1989 Parasound has retained the services of John Curl, for three decades one of the industry's preeminent solid-state designer/engineers, But the realizations of Curl's elegant circuits have typically been compromised by cost-cutting parts substitutions-and sometimes, believe it not, by unauthorized parts additions(!) -- at Parasound's manufacturing facility in Taiwan.

But this time things would be different. Parasound CEO Richard Schram, eager to produce a bulls-to-the-wall flagship amplifier, commissioned John Curl to bring in Bob Crump and Carl Thompson, his partners in CTC Builders, to create a truly great amplifier that could sell for a less-than-stratospheric price tag. CTC Builders might be thought of as a three-headed design superhero -- Curl designs the circuits, Thompson engineers the board layouts, and Crump selects all of the parts, wires, etc., and voices the final product.

CTC had already generated considerable buzz among audiophiles with their no-holds-barred, custom-made-to-order Blowtorch pre-amplifier (at $18,000). This writer had the privilege of reviewing the Blowtorch for the late Ultimate Audio magazine. I, proud owner of the tube-based Thor TA-1000 line and TA-3000 phono preamplifiers -- which had for several years withstood comparisons to various ambitious competitors, found the Blowtorch to be king of the mountain -- the finest audio component in any category that I had ever experienced. Had finances permitted I would have bought one right there.

Following the Blowtorch experience, I was most eager to see what the CTC team could do with the mission of building monster 400-watt monoblocks that would retail for one-third the price of their amazing preamplifier. I lobbied Curl, Crump and Schram, and in due course a sweating UPS driver wrestled two large and heavy boxes into my garage.

"Beautiful brutes." That phrase popped into my head after the JC 1s were unpacked, connected and powered up. The blue front panel ON light was softly evanescent against the beautifully finished silver-toned fascia. Why brutes? A closer inspection revealed signs of amplifiers intended for serious business. The twin banks of sharp-cornered heavy-duty heat sinks occupying both sides of the chassis are impressive. Then there are the RCA and XLR input jacks, the bi-wire loudspeaker terminals, and an unusual complement of back panel toggle switches, for high/low bias selection, and trigger switches for automated power up and down -- all aimed, I suppose, at the home theater market that is a primary target for Parasound. Altogether, the visual presentation belies the $6,000/pair retail price of the JC 1s. Had I just seen the amplifiers with no preparatory information I would have figured the price to be at least double, and possibly more.

The Epic Nobody Wants To Hear
Break-In for the JC 1s was the longest and hardest I have ever experienced, easily surpassing the former record holder, the Meadowlark Blue Heron loudspeakers. Bob Crump had warned that I would have to break in the RCA and XLR inputs separately, but that was the tip of the iceberg. I ran the JC 1s 24/7 (with occasional power down and rest intervals), into massive load resistors that got very warm to the touch, for two months before attempting any critical listening. To my ear they were not nearly ready. Subsequently, stopping to listen every few days, I was increasingly puzzled not to hear the typical linear progression from tight, stiff presentation to more relaxed musicality typically experienced with new amplifiers. Rather, the JC 1s were chameleon-like, ever changing - one time sounding wiry and edgy, another time flabby and bass-heavy. Etc.

These bizarre fluctuations reminded me of a conversation years ago with Francis Mahoney, co-founder of Carneros Creek Winery and a pioneer in upgrading the quality of California Pinot Noir. After I complained that one of his three-year-old Pinots I had just opened had lost the vibrant flavors it exhibited at release, Mahoney explained that many Pinot Noirs go through a "dumb stage" before finally settling into their characteristic flavors. Sure enough, a year later another bottle of the same vintage drank beautifully. Altogether, I spent four solid months of continuous break-in, especially through the balanced inputs, before the JC 1s' sonic presentation became consistent enough for critical listening.

Later, John Curl told me the first batch of JC 1s from Taiwan had come over with steel XLR jacks rather than the specified Neutriks, as well as a few other unauthorized departures from spec (To John's credit, he didn't ask me to re-audition the JC 1s. As far as I know, other reviewers have not experienced the extreme break-in duration I have described, and it may be that my review samples indeed had some unique handicaps.

Life After Break-In!
Finally, the exasperating wait was worth it. It was apparent from the first night of listening to the well-seasoned JC 1s that here were extraordinary amplifiers. The JC 1s control loudspeakers as well as any amplifier I have heard. They pump out seemingly effortless power no matter how insanely loud I push them, with never any sense of strain such as you hear when an amplifier is running out of gas. In that sense of unlimited headroom the JC 1s are very similar to my 750-watt VTL Reference tube monoblocks.

The JC 1s are also capable of wondrous delicacy, and the kind of transparency that makes you feel that you're hearing every instrument, every voice, but never at the expense of the musical whole. Tonality and amplitude are seamless from top to bottom. The bass presentation, to my ear, is flawless -- all the transient speed and slam I could ask for, coupled with a revelatory degree of subtle instrumental differentiation -- able, for instance, to distinguish clearly the combination of soft bass drum strikes, double basses and contrabassoon playing in unison. At the other end of the spectrum, the top octaves seem to extend virtually forever, with no distracting editorial brightness imposed by the amplifiers.

Tube-like? Yes and no. The JC 1s, like the upscale Blowtorch preamplifier, are free from the tonal and harmonic characteristics so commonly ascribed to both tube (romantic lushness, too-soft high frequencies) and transistor (leaner-than-life harmonic structure, mid-treble grain and glare) designs. They serve the music without imposing any distinctive sonic signature.

The JC 1s rank with the best amplifiers I have heard in recreating a multidimensional sound field. Within the performance space they render, individual vocals and instrumentals are stable and consistent. For example, with these amplifiers I do not perceive the Boston Symphony brass edging forward in full cry during the nonpareil 1962 Charles Munch Symphonie Fantastique (beautifully remastered on JVC XRCD2 -- essential). Equally impressive is the impeccable scaling of baroque virtuoso Andrew Manze playing Tartini's Devil's Sonata -- a thrilling evocation of the single instrument interacting with a moderately sized but reverberant space.

Unsurprisingly, the JC 1s are equally happy with rock-'n-roll and other popular genres. I don't remember ever having more fun with the Rolling Stones' great live album Get Yer Ya-Yas Out, or becoming more absorbed into Miles Davis' landmark Kind of Blue (Classic Records 2-LP reissue).

As I have suggested already, the JC 1s are great amplifiers. To be able to buy these robust, delicate, emotionally involving, brilliantly conceived and executed music recreators for $6,000 seems to me little short of a miracle. If I choose to stay with my beloved ($20,000) VTLs, that says more about me -- and my already owning them -- than about the JC 1s. Were I building an elite system from scratch, the JC 1s would be tough to pass up.

I would love to hear the JC 1s against some of the big solid-state muscle amps going for three to six times their price -- Krells, Levinsons, Rowlands, and the current hot-ticket favorite Halros. Who would win? I dunno, But I have little doubt about who would win on bang-for-the-buck. So, do these $6K monoblocks really belong in Superior Audio? Believe me, the honor is ours.

Now that all that subjective opinion is out of the way, let's take a different look at what CTC hath wrought. Note: the following technical highlights are redacted from the considerably longer and more detailed descriptions available from Parasound on the Web.

Design Overview
The JC 1 design is based on a complementary differential J-FET input stage followed by two stages of selected push-pull MOSFETs, ultimately driving 9 pairs of the most powerful complementary bipolar power transistors available today. This produces 400 watts into 8 ohms, 800 watts into 4 ohms, and 1,200 watts into 2 ohms, without compromise.

In a sense, the JC 1 started in 1989 with the Parasound HCA-2200 amplifier, which after a number of prototypes and modifications over the years evolved into the HCA-3500. This amplifier is very powerful, but it lacks the JC 1's much larger heat sinks, twice the power supply, and better connectors, wiring, and circuit layout. The JC 1's "Class A" output is over 25W, so that in normal listening the amplifier operates entirely in Class A, extending to Class AB only during very loud passages, large bass transients, etc.

Bob Crump asserts that the sonic excellence of the parts selected for the JC 1 is unprecedented in an amplifier anywhere near its price range. Those parts include Vampire Direct gold-plated OFC RCA jacks, Neutrik XLR connectors, Reliable RT DC bypass and Zobel capacitors, Superior Electric binding posts, Vampire continuous cast copper signal and DC wiring, Nichicon Great Supply raw DC capacitors (132,000uF in the high-current supply), Nichicon Muse DC and local bypass capacitors, Harris hyperfast soft-recovery diodes for all bridge rectifiers, and Sanken output transistors, the most powerful complementary transistors available. The JC 1 has separate power supplies for the input/driver section, making it immune to fluctuations in AC line voltage.

Circuit functions are divided between four separate, carefully oriented circuit boards and their associated wiring to minimize unwanted circuit interactions. System signal flow emphasizes overall system grounding. The final main board can handle double the very substantial current the JC 1 can deliver. This capacity requires very wide matched circuit paths in 2 oz. copper on both sides of the board for critical nodes.

Audible strain due to layout-generated resistance is negligible. The beefy layout accommodates the huge power supply, which comprises four large filter capacitors, plus the separate input stage power supply on the main circuit board. The separate dedicated input board is thus more immune to power supply and circuit noise. The input board mounts directly on the back panel for minimum wiring length. The layout is symmetrical, with the shortest possible signal paths.

Technical Notes
Power Supply: The heart of the power supply is a 10 ampere (continuous) toroidal transformer encapsulated in an epoxy-filled steel canister to ensure ultra-quiet performance.

The high-voltage B+ and B- supply rails for the output stage use high-speed fast-recovery rectifier diodes and four 33,000 uF Nichicon electrolytic filter capacitors. These filter capacitors are bypassed with smaller polypropylene capacitors to reduce AC ripple in the DC supply and further eliminate AC noise and interference generated by computers and other appliances.

Relay-Bypassed Soft Start Circuit: When the JC 1 is turned on, significant inrush current is required to charge the power supply capacitors. To suppress this inrush current and prevent nuisance tripping of circuit breakers, NTC (negative temperature coefficient) resistors reduce the inrush current by 50 percent. After that, a gold contact relay activates to completely bypass the NTC resistors to ensure that they do not restrict the power supply during operation.

Complementary Configuration: Each stage of amplification uses NPN transistors fed by the positive DC power supply and complementary PNP transistors fed by the negative DC power supply. This complementary topology is inherently linear, which reduces distortion and improves sonic accuracy.

Input Stage: The JC 1's input stage uses matched pairs of discrete JFETs arranged in a differential configuration. JFETs are ideal for the input stage because their inherently high impedance is unaffected by the impedance of source components. Differential configuration provides superior noise reduction. These precision input JFETs are also cascaded to produce the current necessary to drive the MOSFET drivers in the following stage.

Driver Stage: The driver stage employs complementary matched pairs of MOSFETs selected for their tube-like sonic qualities. MOSFETs tend to generate less odd-order harmonic distortion than bipolar transistors. This is important because odd-order distortion sounds unnatural and fatiguing to the human ear, whereas even-order distortion is less offensive because it is consonant, rather than dissonant. The B+ and B- power for the input and driver stages cannot sag under load because it is supplied by independent transformer secondary windings with independent rectification, filtering and voltage regulation. This preserves soundstage width and depth even when the JC 1 output stage is drawing enormous amounts of current.

Output Stage: The JC 1's output stage employs nine pairs of high-current (15-ampere) bipolar transistors to ensure long-term reliability with continuous high power operation and challenging speaker loads. Lightning-fast (60MHz) transistors respond instantly to complex demands in the musical signal, virtually eliminating distortions that occur with slower transistors. Slew rate limiting and Transient Intermodulation Distortion (TIM) are simply not an issue.

"Class A/AB" Operation: Pure "Class A" operation provides the purest sound. However, an amplifier operating entirely in "Class A" operation would be enormous, highly inefficient, and generate too much heat. "Class AB" combines some of the advantages of "Class A" with the efficiency of "Class B" operation. It is a compromise that reduces the heat generated in pure "Class A" operation and the odd-order harmonic distortion created in "Class B". In "Class AB", the driver and output stages are always turned on, which provides a nominal amount of pure "Class A" operation. The JC 1 input and driver stages are 100% pure "Class A", while its output stage provides up to 25 watts of pure "Class A".

DC Servo: Direct Current (DC) burns out speakers. Therefore, every power amplifier must have some way to ensure that DC from its power supply never reaches its + or - speaker terminals. Most amplifiers use trim controls to reduce DC offset or capacitors to block DC. Unfortunately, trim controls can allow DC offset to increase over time, and even the most expensive capacitors in the audio signal path will veil sonic clarity and attenuate bass response. The JC 1 incorporates fast-acting DC servo circuits, eliminating the need for coupling and blocking capacitors. The JC 1 is direct-coupled from input jack to speaker terminals. This circuitry never needs adjustment or maintenance. It operates outside the audio signal path to keep the DC offset at the output of the JC 1 at a constant 0.00 Vdc.

Relay Protection: When the JC 1 is powered on, the protection relay remains open for three seconds while the positive and negative power supplies stabilize. This prevents annoying popping or other transient noises. Relay protection also prevents speaker damage in case of a catastrophic amplifier failure.

Over-Current Protection: Current-sensing transistors connected to the output stage constantly monitor current flow through the output transistors. If the current exceeds a predetermined safe level due to load impedance below 1 ohm or a short circuit at the speaker terminals, the output relay opens immediately to prevent output transistor or other parts failure.

Fuse Protection: Separate fuses for the positive and negative DC voltage rails provide backup protection in case the over-current protection does not work in time or an internal part fails. In the event of a part failure, these fuses halt operation to minimize damage to additional parts.

Chassis: The chassis is heavy-gauge aluminum. Aluminum is non-magnetic and cannot be energized by high voltage and current flow, thereby removing a potential cause of "smearing" or other audible intrusion.

Specifications
RMS Power, 20Hz to 20kHz: 
400 watts continuous, 8 Ohm 
800 watts continuous, 4 Ohm 
1200 watts short term, 2 Ohm 

Class A Power, 20Hz to 20kHz 
25 watts, bias set to high, 8 Ohm 
10 watts, bias set to low, 8 Ohm

Current Capacity: 135 amperes peak

Slew Rate: >130 V/µsecond

Frequency Response: 2Hz to 120 kHz (+0/-3dB)

Total Harmonic Distortion: <0.15% at full power; < 0.018% typical levels

IM Distortion: <0.03%

TIM: Unmeasureable 
Dynamic Headroom: >1.8dB

Input Impedance: Balanced 100 k Ohms; Unbalanced 50 k Ohms

Input Sensitivity: 
Balanced - 1 V for 28.28 V output into 8 Ohms 
Unbalanced - 1 V per leg for 28.28 V output into 8 Ohms

Signal to Noise Ratio: 
>122dB, IHF A-weighted, bias set to low 
>120dB, IHF A-weighted, bias set to high 
>113dB, Unweighted, bias set to low 
>111dB, Unweighted, bias set to high

Damping Factor: >1200 at 20Hz

DC Trigger Requirements: +9 Vdc to +12 Vdc, 2 mA

Audio Trigger Requirements: 50-250 mV AC

DC Trigger Output Capacity: +12 Vdc, 150 mA

Dimensions: 
Total Width: 17.75 x 7.8 x 20 (WxHxD in inches)

Net Weight: 64 lb.

Price: $6,000 per pair

Company Information
Parasound Products, Inc.
950 Battery Street
Second Floor
San Francisco, CA 94111

Voice: (415) 397-7100
Fax: (415) 397-0144
Website: www.Parasound.com