Phono Preamplifiers

A quick comparison between the ‘inside shot’ on Page 2 of this review and that of the JC3+ [HFN Oct ’15] clearly reveals the stripped-down build of this ‘Junior’ version. Nevertheless it’s almost as if circuit and board designers John Curl and Carl Thompson had read our Lab Report published over two years ago because, in practice, the JC3 Jr offers a broader range of gain settings (three rather than two) and a better balance between its input sensitivities and input overload capacity. The specified +40dB, +50dB and +60dB gain options work out as +46.7dB, +56.7dB and +66.3dB via the JC3 Junior’s balanced outputs, equivalent to input sensitivities of 4.58mV, 1.46mV and 486µV respectively.

The lower sensitivity ‘+40dB’ option is better suited to high output MMs from the likes of Ortofon than the +50dB minimum setting of the flagship JC3+ and supports this with a healther 70mV input overload ceiling – a margin of +22.9dB for a standard 5mV MM (re. 1kHz/5cm/sec). The intermediate ‘+50dB’ option is ideal for lower output MMs and high output MCs where the JC3 Junior will yield its optimum 90dB A-wtd S/N ratio. With both +40dB and +50dB settings, the RIAA-eq’d distortion remains as low as 0.0012-0.012% from 20Hz-20kHz [see Graph 2]. The highest ‘+60dB’ option offers a useful input headroom of +23.9dB for standard 500μV MC pick-ups, although the lowest output MCs will not realise the potential 74dB A-wtd S/N ratio. Parasound’s penchant for subtly adapting the RIAA response continues here with a subsonic roll-off of –3dB/7Hz (missing in the JC3+) followed by a mild +0.3dB bump in the low bass before reaching out to 100kHz ±0.3dB. The L/R channel imbalance at HF is insignificant [see Graph 1]. PM

Input loading (MM/MC): 47kohm / 50-550ohm
Input sensitivity (re. 0dBV balanced out): 4.58mV / 1.46mV / 486µV
Input overload (re. 1% THD): 70mV / 23mV / 7.8mV
Max. output (re. 1% THD) / Impedance: 15.6V / 96ohm (balanced)
A-wtd S/N ratio (re. 0dBV balanced out): 82.7dB / 90.1dB / 73.9dB
Frequency resp. (20Hz-20kHz/100kHz): –0.1dB to +0.32dB / +0.18dB
Distortion (20Hz-20kHz, re. 0dBV): 0.0012–0.012%
Power consumption: 8W
Dimensions (WHD) / Weight: 437x64x375mm / 5.9kg
Price: £2299