Pre/Power Amplifiers

It's not part of the sales pitch, and you'll not read this in any other reviews, but Jadis is offering us two preamplifiers in one with its JPL MkII. It all comes down to the choice of CD versus Aux/Line inputs. Sure enough there's the expected difference in overall gain (+6.5dB for 'CD' and +19dB for 'Line' – neither close to the specified +25dB) and while the A-wtd S/N ratios are almost identical at 90.5dB (re. 0dBV), the difference in tube complement – a single-stage ECC82 for 'CD' and two-stage ECC83 for 'Line' – results in markedly different trends of THD vs. frequency and output. Choose 'CD' for full-on tube colour with distortion at ~0.35%, or 'Line' for a solid-state-like linearity of 0.00035-0.0035% [re. 0dBV, 20Hz-20kHz, see Graph 2]. Output impedance is a high ~950ohm (though the SE300B's 100kohm input renders this moot) while the response is slightly more rolled off via 'Line' at –0.1dB/20kHz to –2.4dB/100kHz.

While on the subject of 'colour', the partnering SE300B monos painted their test results with a vivid palette! Power output meets the rated 10W at 10.5-11.5W into 8-4ohm loads at 1% THD, increasing marginally to 14.5W at 2% THD and 15.5W at 3% THD and, under dynamic conditions, to 13.5W, 15.5W, 9.0W and 5.1W into 8, 4, 2 and 1ohm loads [see Graph 1]. Overall gain is +26dB and the A-wtd S/N ratio slightly below average at 82dB (re. 0dBW) while midband distortion increases gently with level from 0.08%/100mW to 0.22%/1W and 0.52%/5W. Versus frequency there's a steep rise in THD below 300Hz to 4.5% at 200Hz, 14.5% at 100Hz and 35% at 40Hz – all at just 1W/8ohm [pink trace, Graph 2]. I discuss the impact of the SE300B's response and output impedance with DeVore's O/96 speakers in its lab report. PM