Parasound - Halo JC 3+ Phono Preamplifier

Parasound has introduced an improved version of its Halo JC 3 phono preamplifier. The new Halo JC 3+ adds independent load adjustment for moving coil cartridges, as well as enhancements to the dual-mono phono module circuit boards, and increased power supply capabilities. The JC 3+ circuit comes from the designer of the legendary Vendetta phono preamp, John Curl.

"Six years ago Parasound asked John Curl if he would create a reasonably priced Parasound Halo phono preamp with ultra low noise, in the spirit of his masterpiece, the Vendetta," said Richard Schram, the founder of Parasound. "Three years later we introduced the remarkable Parasound Halo JC 3 which has earned rave reviews from the audiophile press and a legion of vinyl enthusiasts."

During the design phase of the JC 3, Curl had rejected variable load adjustment because, compared with fixed resistors, potentiometers generally have higher intrinsic self-noise, which is an anathema to creation of an ultra-low noise phono stage. Curl prevailed (he always does), and the JC 3 was built with limited switched input load impedance choices. This decision disappointed some vinyl enthusiasts and reviewers who consider input load fine-tuning to be essential for certain cartridges.

Curl and circuit board designer Carl Thompson eventually consented to including variable load impedance adjustments, but with these caveats for the potentiometers: 1) They must comply with stringent performance requirements. 2) They must be manufactured by Vishay, a highly-regarded manufacturer of low-noise electronic parts. At that time Vishay did not offer a potentiometer that met these specific requirements. However they recognized an opportunity, and eventually agreed to develop the part and manufacture it in small quantities for Parasound. The outcome of this effort is the Parasound Halo JC 3+.

Naturally, the JC 3+ features independent variable MC load fine adjustment capability for each channel from 50-550 ohms using these special low-noise dual-gang potentiometers.

Parasound also took the opportunity to make additional performance improvements. Curl narrowed the spectrum of Johnson/Nyquist noise in the resistor that loads the input stage to maximize its low noise capabilities. Circuit-board designer Carl Thompson tweaked the phono module board layouts to further optimize every performance parameter. The copper circuit board traces in the phono modules are now 24 karat gold-plated where each part is soldered to provide unprecedented transparency and musical detail.

The MC signal to noise ratio is improved from 75dB to 87dB, A-weighted. MM gain has been increased slightly from 47dB to 48dB, while MC gain has been lowered from 68dB to 64dB so extra-high output MC cartridges won't cause the JC 3+ to overload the inputs of some line stage preamps.

"Where the JC 3 background was utterly 'black,' the JC 3+ black is, well, blacker." notes Schram. "While these may seem like small details, the JC 3 is already an incredible performer and Parasound is going for that little bit more in the JC 3+."

The JC 3+ power supply has also been significantly upgraded with 47 percent larger low-ESD power supply filter capacitors. This provides much greater current reserves for head-snapping dynamics. A new R-core power transformer is 82 percent larger to provide greater reserves for low-end impact that's beyond imagination.

Finally, at the suggestion of a few JC 3 customers, the company has added a simple on/off switch for the front panel P logo illumination.

• Frequency Response:  20Hz - 20kHz, +/- 0.2dB
• Total Harmonic Distortion:  < 0.01% at 1kHz
• Signal to Noise Ratio, MM:  > 87dB, input shorted, IHF A-weighted & > 78dB, input shorted, unweighted
• Signal to Noise Ratio, MC:  > 87dB, input shorted, IHF A-weighted & > 67dB, input shorted, unweighted
• Interchannel Crosstalk:  72dB at 1kHz
• Input Impedance: 47k Ω (MM) & 50 - 550Ω variable or 47k Ω fixed (MC)
• Output Impedance:
• Unbalanced: < 100Ω
• Balanced: < 100Ω per leg
• Input Sensitivity at 1 kHz: 4mV for 1V output (MM) & 600μV for 1V output (MC)
• MC: 600μV for 1V output
• Total Gain: 48dB (MM) & 64dB (MC)
• XLR Pin Identification: 1 = Ground (Shield), 2 = Positive, 3 = Negative (Return)
• AC Power Draw: 1 watt (Standby), 12 watts (Power On)
• AC Power Requirement: 115 or 230 VAC 50 - 60 Hz (Selected on Chassis Bottom)
• Dimensions (WxDxH): 17-1/4” x 13-3/4” x 4-1/8” (w/feet) or 3-1/2” w/o feet)
• Weight: 19 lbs. (Net) & 26 lbs. (Shipping)