Integrated Amplifiers

While the Diapason Luxe is intended as a stepping stone into Jadis's world of artisan audio, this low-powered amp still employs the choice passives and tubes that we've seen in its far costlier single-ended designs. This integrated is a push-pull design, and biased into Class AB, but Jadis's customarily enigmatic specification still holds sway – power is rated at '15W' without reference to load, distortion or frequency! In practice the available power rather depends on the level of distortion you'll tolerate, increasing from 0.2%/0.5W to 0.4%/1W, 1%/2.9W, 2%/6W and 3%/11.6W (all 1kHz into 8ohm via the 8ohm tap or 4ohm via the 4ohm tap). Relaxing our tolerance to 5% THD, and testing the Diapason Luxe under dynamic conditions (1kHz/10msec), reveals a significantly higher 26W (8ohm tap), 26W (4ohm tap), 27W and 17W into 8, 4, 2 and 1ohm loads, respectively [see Graph 1, below]. So while these are not high figures, and sensitive speakers are a must, the amp will still likely sound louder than you might expect.

The tonal balance, however, is influenced by both its high 2.4-4.06ohm source impedance and the increase in distortion either side of the midrange. At just 1W/8ohm THD is lowest at ~0.5% from 200Hz-2kHz while the limited feedback allows 1%/6kHz to 2.5%/20kHz [Graph 2, below]. Transformer core saturation is also at least partially responsible for the increase in THD at low bass frequencies – 1.9%/1W up to 5.5%/5W (both 20Hz/8ohm). Cautious compensation typically means a higher overall gain (+38.2dB) and, in this instance, a slightly below-average 78.5dB A-wtd S/N ratio (re. 0dBW), the latter a combination of both hum and white noise. PM