Halo JC 1+ 
Parasound’s Ultimate Amplifier 
 
The following is written by 
Richard Schram
President / CEO, Parasound Products, Inc.
 
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The origin of the JC 1+ 
An audio historian could make a persuasive case that our new Parasound Halo JC 1+ is the most ambitious and extraordinary achievement since I established the Parasound brand in September 1981.
 
For almost 40 years our mission has remained the same: build audio components that sound better, measure better and last longer than our competition, at prices that are sensible. We call this “value engineering.” It challenges us and guides every decision we make for every product we build.
 
The origins of the JC 1+ go back to 1989 when we engaged the legendary John Curl to design our power amplifiers. These were very successful, so in 2000 we commissioned Curl to develop the JC 1. Released in early 2003, the JC 1 immediately earned the respect and admiration of reviewers and audiophiles alike. It set new standards of performance and value that were unrivaled during its 16 years in production. In fact, the last JC 1 to come off the production line sounded just like the first JC 1. There were no “improved” versions during its entire product life -- simply because the JC 1 design, development, and manufacture made it so far ahead of its time.
 
A few years after the JC 1’s introduction, consumers and dealers began asking when we planned to build an improved JC 1. After all, this is a common practice in the audio industry (which makes me wonder, why couldn’t they get it right in the first place?). My reply was always the same: “We could make changes to increase its price, but none that would materially improve performance. Yes, we could make a more expensive JC 1 and, if we were lucky, it might sound as good as the existing JC 1”.
 
In early 2014, John Curl announced that he was investigating ideas that could substantially improve the JC 1 performance. As all Curl’s theories are based on objective science, not wishful thinking or self-suggestion, I was all ears.
 
It’s prudent to be skeptical of new ideas, and we were. So Parasound hand-built six experimental prototypes to test Curl’s theories. What we measured and heard were nothing short of astonishing. The JC 1+ decisively outperformed the JC 1 in every respect.
 
New insights
Most amplifier manufacturers don’t allocate resources to develop their input and driver stages because they either fail to understand their critical role or they just don’t want to spend the money. Curl, on the other hand, knows that an amplifier can only be as good as its input stage. Input and driver stages that provide the amplifier’s voltage gain have a significant influence on an amplifier’s performance. If an amplifier’s input and driver stages are even slightly deficient, the very best output stage cannot make up for its shortcomings. Such an amplifier won’t meet our standards.
 
Curl addressed the most prevalent shortcomings of amplifier input stages. First among these is distortion that originates in the input stage. Even the slightest amount of input stage distortion becomes significant by the time it reaches the amplifier’s output stage and ultimately, your speakers.
 
Input stage distortion is often caused by insufficient power supply voltage. Any amplifier will distort if its input and driver stage B+ and B- power supply rail voltage “sags”. Yet in virtually all amplifiers, the input stage power supply is shared with the output stage supply. Typical input stages and driver stages derive their operating voltage from the output stage power supply. This invites distortion whenever the amplifier is played at high volume.
 
Voltage drops occur when the power transformer, bridge diodes and filter capacitors aren’t substantial. The original JC 1 avoided voltages drops by equipping its power transformer with additional secondary windings solely for the input and driver stage power supply.

The Halo JC 1+ goes a step further with the addition of a separate power transformer dedicated to the input and driver stages. This second power transformer supplies ± 89V to high-speed soft-recovery bridge diodes and Nichicon filter capacitors totaling 22,400uF, resulting in rock-solid ±112Vdc for the B+ and B- “rails” when the amplifier’s output stage is operating at its maximum capacity.

A miniscule amount of power supply noise contaminates the input and driver stages, with sonic consequences that are aptly described as “grunge.” The JC 1+’s independent power transformer for the input and driver stages assures sonic refinement by addressing the problem of noise ‘hitchhiking’ on the AC power line. For this application, Curl specified
an “R-core” transformer rather than a more conventional toroid transformer. The unique architecture of an R-core transformer minimizes capacitive coupling between its primary winding and secondary winding. This minimizes AC noise that could contaminate the input and driver stages. Instead the JC 1+ input and driver stage voltage is dynamic
and pristine. 
 
 
Supremely silent
Curl is a master at eliminating undesirable electronic noise. For the JC 1+ he specified a pair of Bybee Music RailsTM, which are active high frequency noise filters that “scrub away” every vestige of noise on the input and driver stage B+ and B- rails. These ingenious and patented devices were conceived by Jack Bybee and invented by an eminent microwave engineer and audiophile in collaboration with Curl and noted circuit board designer Carl Thompson. Carl is known for designing the circuit boards for Curl’s Vendetta Research phono stage, and the Parasound JC 1, JC 2 BP, JC 3+ and JC 3 Jr. To optimize their effect, Carl designed Music Rail circuit boards exclusively for the JC 1+. The JC 1+ is the first commercial product to employ these remarkable devices.
 
As in the JC 1, the JC 1+ input stage uses hand-matched pairs of Toshiba 2SJ74 P-channel and 2SK170 N-channel J-FETs. These coveted devices remain unmatched for their low noise. Parasound is one of the few companies that has invested heavily to secure an ample stock of these rarest of all J-FETs.
 
The JC 1+ employs FR408 circuit board substrate for the critical input and driver stages. FR408 was invented for ultra high-speed applications in super computers and aerospace. Carl recommended FR408 for its superior propagation of high frequencies that outperforms Delrin. Our obsession with eliminating noise that pollutes sound quality led us to add shielding to this board to isolate it from internal stray currents that might diminish its perfection.
 
The JC 1 driver stage was an excellent single-stage circuit. Curl predicted that a two-stage cascode driver would make a substantial performance improvement because a driver circuit with cascode topology has some of the favorable attributes of vacuum tubes, namely higher input-output isolation, higher input impedance and higher output impedance. Its greater bandwidth and open loop gain were expected to improve linearity and a noticeable improvement in sound quality. This proved to be true.