Power amplifiers mono — Parasound JC1+

The JC1+ is a monoblock power amplifier from Parasound built around a circuit by John Curl, priced at USD 8,500 per unit and offered in silver or black finishes. Two units form a stereo pair. It replaces the JC1 with more power, a larger power supply and a higher output transistor count.

Key specs that matter

Each unit delivers 450 W into 8 ohm, 850 W into 4 ohm and 1,300 W into 2 ohm, and the first 25 W run in Class A with bias set high, or 10 W with bias set low. Full power is rated down to 2 Hz. Peak current capacity is 180 A and slew rate exceeds 130 V per microsecond. Frequency response is 2 Hz to 120 kHz within +0/-2 dB and 20 Hz to 20 kHz within +0/-0.25 dB. THD is below 0.15 percent at full power and below 0.02 percent at typical listening levels, with IM distortion below 0.03 percent. Measured IHF A-weighted, the signal-to-noise figure is over 122 dB at low bias and over 120 dB at high bias. Damping factor exceeds 1,200 at 20 Hz. Input impedance is 50 kohm unbalanced and 100 kohm balanced, and gain is switchable between 29 dB and 23 dB. The chassis is 448 mm wide, 181 mm high without feet and 508 mm deep, and weighs 37.6 kg net or 48.5 kg for shipping.

Engineering and use context

The direct-coupled signal path contains no capacitors or inductors, with a JFET input stage, a new cascode MOSFET driver stage and 24 beta-matched Sanken 60 MHz bipolar output transistors. A 2.1 kVA shielded toroid with an H18 grade core feeds six 33,000 uF Nichicon Gold Tune capacitors, for 198,000 uF of filtering, while an R-core transformer and 22,400 uF supply serve the input stage separately. Bybee Music Rails active filters sit on the input stage rails. The output boards use double-thickness copper, the input circuit board is shielded, and Harris hyper-fast soft-recovery bridge rectifiers work with REL and Nichicon Muse capacitors. Protection includes a DC servo, relays and AC inrush surge limiting. Idle draw is 145 W at low bias and 275 W at high bias, typical draw is 400 W and the maximum is 1,500 W.

Pairing

Both XLR and gold-plated RCA inputs are fitted, with a looping XLR output for bi-amping from one source feed. Dual CHK Infinium 5-way binding posts accept bi-wired cables. The amplifier switches on through a 12 V trigger or by audio sensing, and rack hardware for four spaces is included. A front panel LED indicates status.

Alternatives

The Parasound JCM250 is a smaller John Curl monoblock rated at 250 W into 8 ohm in a two-rack-unit chassis.