Developed by John Curl: Cutting-Edge 450Wpc Parasound JC 1+ Mono Amplifier Offers 25 Watts of Pure Class A, Operates with Extreme Silence, Provides Supreme Driving Power
The Parasound JC 1+ is nothing less than the finest-performing mono power amplifier in the company's fabled four-decade history – and arguably the most inspired creation ever made by legendary designer John Curl. Developed over the course of five years, and held back for a full year of rigorous testing even after Curl and his associates signed off on its completion, JC 1+ stands as one of the quietest-operating and profoundly dynamic amplifiers you'll ever have the fortune to encounter. Simultaneously, this Curl-dubbed "stump puller" provides 180 amps of peak current – enough to drive literally any commercially manufactured speaker with ease. Curl engineered JC 1+ to practically be allergic to distortion – and all its negative impacts, including listener fatigue.
Offering 25 watts of pure Class A power, able to deliver 450 watts into eight ohms and 850 watts into four ohms, and boasting a direct-coupled signal path, JC 1+ epitomizes high-end might, high-fidelity sonics, and high-performance integrity. Incredibly, the 83-pound unit remains stable with speaker impedance dips below one ohm and includes a gain switch (29dB or 23dB) for optimal compatibility with high-gain preamplifiers and ultra-efficient speakers. Independent power supplies for the JFET input stage, MOSFET driver stage, and output stage abet a 2.1kVA shielded power transformer with premium H18-grade core. Equally notable, JC 1+ employs a pair of Bybee Music Rails – active high-frequency noise filters that scrub away every vestige of noise on the input and driver stage B+ and B- rails. To optimize their effect, noted audio designer Carl Thompson created Music Rail circuit boards exclusively for JC 1+.
Such hyper-meticulous mechanical and technical details proliferate throughout JC 1+. For starters: Its driver stage employs a new cascode circuit design for tremendous open-loop bandwidth and supreme linearity; an R-core power transformer for the crucial input stage suppresses power-line noise; six mammoth 33,000uF Nichicon Gold Tune filter capacitors are employed for the output stage; and 22,400uF input power supply filters exist independent of the main power supply. And the spoils continue – gold-plated internal signal-path connectors, 24 beta-matched 15A/230V/60MH bipolar output transistors, Harris soft-recovery bridge diode rectifiers, REL and Nichicon Muse capacitors, ample shielding, and DC servo and relay protraction circuits included.
While the sleek front panel remains straightforwardly elegant with a power LED indicator, the back panel speaks to JC 1+'s functionality. A two-position toggle switch (to select normal bias and 25 watts in pure Class A or lower bias and 10 watts in pure Class A), gain toggle switch, and AC master switch abet a clean layout featuring balanced Neutrik locking-type XLR input and loop input connectors as well as unbalanced Vampire RCA input and loop output connectors – making it simple to connect multiple JC 1+s for bi-amping or looping the signal to a subwoofer equipped with an XLR input. Two pairs of proprietary 24k-gold-plated spinner-style speaker terminals accept up to 16mm-wide spade lugs, bananas, and up to 5AWG bare wire. JC 1+ even boasts auto turn-on circuits with 12V trigger jacks and provided rack-mount hardware.
In every regard, JC 1+ will do for your music what you've likely only dared to dream. Parasound's five-year manufacturer warranty and our 100% Music Direct Satisfaction Guarantee ensure your fantasies become realities.
"Using the Parasound JC 1+ in two separate listening rooms and with four different speakers, my impressions are thus: These amps have a cleanliness and abundance of power that works very well to unlock the potential in a lot of speakers, especially ones with a complex crossover and large impedance swings. The sound has plenty of detail, without being etched or glassy sounding. Imaging properties are truthful if not voodoo-like. The Parasound JC 1+ does many things very well and nothing wrong. I was truly engaged on many nights while listening."
—Dave McNair, Part-Time Audiophile
"This is a superb-sounding amplifier that will get the best from every loudspeaker with which it is partnered. Well done, Mr. Curl."
–John Atkinson, Stereophile
"The sound is exemplary and one would expect that from the...price, but high price is no guarantee of quality for any product. It has to be verified. Proof of Performance for the Parasound has been verified. They are worth the price."
–The Secrets of Home Theater and High Fidelity, 2020 Best Monoblock Power Amplifier Award
"If this amplifier had a boutique-y badge on the front panel, you'd ay $50K for a pair of these, and be on social media tomorrow bragging about them. That's why at [the price], they are the big amplifier deal of all time."
–TONEAudio, Product of the Year Award
New Amplifier Design 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. John 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 Parasound 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. 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 minuscule amount of power supply noise contaminates the input and driver stages, with sonic consequences that are aptly described as "grunge." 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.
John Curl is a master at eliminating undesirable electronic noise. For JC 1+, he specified a pair of Bybee Music Rails that 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 JC 1+, the first commercial product to employ these remarkable devices. As in JC 1, the JC 1+ input stage uses hand-matched pairs of Toshiba 2SJ74 P-channel and 2SK170 N-channel JFETs. 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 JFETs. 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. Parasound's obsession with eliminating noise that pollutes sound quality led it 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.
High Current Is Imperative
John Curl affectionately referred to JC 1 as a "stump puller" because its 135 amp peak current enabled it to drive any commercially manufactured speaker with ease. Over the years, he has observed an increasing number of high-performance speaker manufacturers employ lower impedance to achieve their sonic objectives. Impedance dips below two ohms are not uncommon. Such punishingly low impedances increase an amplifier's odd higher-order harmonic distortion, a primary cause of listening fatigue. Driving low-impedance speakers doesn't necessarily require more watts, but higher current is imperative. Parasound raised the JC 1+ peak current to 180 amps with the addition of six Sanken 15A/230V/60Mz bipolar output transistors, for a total of 24. Accommodating six more output devices necessitated changing the output stage circuit board's orientation from horizontal to vertical. This added welcome benefits of more effective heat dissipation and easier serviceability. To conduct higher current flow in the JC 1+ we made the copper traces on its main circuit board and N and P channel output stage circuit boards twice as thick as on JC 1. Supporting this substantial current required an even more potent power transformer. The massive 2.1kVA transformer weighs 30 lb. Developing this power transformer was challenging and required 11 hand-made samples before Parasound achieved the necessary power and total absence of mechanical vibration. The JC 1+ power transformer accomplished this with an especially potent and expensive steel core. To unleash greater dynamics, JC 1+ uses six 33,000uF Nichicon Gold Tune capacitors, a prodigious total 198,000uF. Gold Tune capacitors are among the finest capacitors ever designed specifically for high-end audio applications. Although these Gold Tune capacitors were discontinued years ago, Nichicon continues to manufacture them exclusively for Parasound.
450 x1 watts @ 8 Ω
850 x1 watts @ 4 Ω
1300 x1 watts @ 2 Ω
Power measurements are with 120 VAC: 0.15% THD, RMS continuous power, full audio band (20 Hz - 20 kHz)
Class A Power Output:
25 Watts, bias switch set to high
10 Watts, bias switch set to low
Current Capacity: 180 amps, peak
Slew Rate: > 130 volts per microsecond
2 Hz - 120 kHz, +0/-2 dB
20 Hz - 20 kHz, +0/-0.25 dB
Total Harmonic Distortion (THD):
< 0.15 % at full power
< 0.02 % at typical listening levels
IM Distortion: < 0.03 %
Damping Factor: > 1200 at 20 Hz
Unbalanced: 50 kΩ
Balanced: 100 kΩ, (50 kΩ per leg)
S/N Ratio, inputs shorted:
>122 dB, IHF A-weighted, bias set to Low
>120 dB, IHF A-weighted, bias set to High
>113 dB, Unweighted, bias set to Low
>111 dB, Unweighted, bias set to High
29 dB (Gain switch set to normal)
23 dB (Gain switch set to low)
Input Sensitivity for 28.28 V Output into 8 Ω:
Unbalanced: 1 V
Balanced: 1 V per leg
DC Trigger Requirements: +9 Vdc to +12 Vdc, 5 mA
Audio Trigger Requirement: 2.5 mV - 10 mV
XLR Pin Identification:
1 = Ground (Shield)
2 = Positive
3 = Negative (Return)
Standby: <1 Watt
Idle (bias set to low): 145 Watts
Idle (bias set to high): 275 Watts
Typical Listening levels: 400 Watts
Maximum: 1500 Watts
Dimensions (HD): 7-1/8" x 20"
Weight: 83 lbs.
User Manual (PDF, 3.4 MB)