Integrated Amplifiers

Although the IA350A embodies many of YBA's core design ideals, it is not a 'half power' version of the AMP650 [HFN May '18]. I discuss the relatively low +23.6dB gain and cleverly sculpted frequency response offered by the IA350A in my boxout, and while it does betray a similar 2nd/3rd harmonic distortion trend to the AMP650 (consistent at ~0.02-0.03% over 1-80W/1kHz/8ohm) the levels of PSU noise are lower and the A-wtd S/N improved by 10dB to 81.5dB (re. 0dBW). Versus frequency the modest levels of compensation (feedback) employed by YBA mean that distortion climbs quickly above 10kHz, reaching 0.14%/20kHz and 0.35%/40kHz at 10W/8ohm. Subjectively this is not troublesome because the harmonics lie well outside the audioband. Power output is just within specification at 2x120W/8ohm and 2x180W/4ohm while there's sufficient latitude in the power supply to accommodate 163W, 302W and 450W into 8, 4 and 2ohm loads under dynamic conditions [see Graph 1, below].

The digital board is based on the (very) tried-and-tested CS4398 DAC, originally launched in 2002, and supporting up to 192kHz/24-bit LPCM. Maximum preamp output here is 2.3V from a 96ohm source impedance, the stage offering a generous 107dB A-wtd S/N ratio and a response that rolls away to –0.13dB/20kHz with CD/48kHz media down to –1.7dB/45kHz (96kHz files) and –7.5dB/90kHz (192kHz files). Jitter is well suppressed (typically ~75psec) and while distortion increases slightly over the top 10dB of its dynamic range [see Graph 2, below] reaching 0.0006-0.009% at 0dBFs, it drops to a minimum of 0.0005-0.0006% at –15dBFs. PM