Integrated Amplifiers

No stranger to triode tube/transistor hybrid amplifier designs, Unison Research's new Due model is not a trimmed down version of its heavyweights like the Unico 90 [HFN Aug '17]. Rated at 100W/8ohm and 180W/4ohm the Unico Due actually delivers more than the Unico 90 at 2x125W/8ohm and 2x205W/4ohm with a dynamic output of 153W, 280W, 331W and 200W into 8, 4, 2 and 1ohm (limited to 14A). Distortion increases with level from 0.06%/1W to 0.18%/10W to 0.59% at the rated 100W/8ohm, but – very unusually – distortion is uniformly lower when the Unico Due is driving tougher 4 and 2ohm loads [see Graph 1].

Distortion is also very uniform indeed with frequency – a function of the tube stage, perhaps – but the A-wtd S/N ratio is impacted by white noise, yielding just 81dB (re. 0dBW). The frequency response reaches a wide –0.1dB/20kHz and –1.4dB/100kHz. The digital board is based on the 'mobile' version of the tried-and-tested ES9010K2M DAC, connected by a length of ribbon cable around the back of the amp to the 'input' PCB and 'USB out' RCAs. Maximum output here is 1.47V from a moderately high 447ohm source impedance, the stage offering a fair 104dB A-wtd S/N ratio and a response that rolls away to –1.8dB/20kHz with CD/48kHz media down to –9.8dB/45kHz (96kHz files) and –21dB/90kHz (192kHz files). Jitter is well suppressed (typ. <10psec) but distortion increases over the top 20dB of its dynamic range [see Graph 2] reaching 0.065-0.075% at 0dBFs and falling to a minimum of 0.006-0.008% at –20dBFs. This is not low by modern standards but remains impressively consistent with frequency [black/blue traces, Graph 2] and – importantly – lower than that of the main amplifier itself. PM