Pre/Power Amplifiers

Tested in 'Direct' mode, the P-80's RCA in/XLR out analogue preamplifier offers a maximum 8V output from a 220ohm source impedance – overall gain is +21.5dB and the maximum (single-ended, RCA) analogue input level is 4.2V. Distortion falls to a minimum of 0.0007-0.0008% at 0dBV (1V) output (re. 20Hz-20kHz), which is lower than achieved by the DAC stage [see below]. The 100.8dB A-wtd S/N ratio (re. 0dBV) is good and the frequency response very extended at +0.0dB to –0.07dB (20Hz-20kHz), reaching out to –1.6dB/100kHz.

The AK4452 DAC-based digital section offers a maximum 7V balanced (XLR) output with peak (0dBFs) inputs – the volume control is between 2 and 3 o'clock at this point. Onkyo has chosen a medium roll-off linear phase digital filter that offers a 73dB stopband rejection and responses that reach out to –0.4dB/20kHz, –2.2dB/45kHz and –6.4dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively. In this implementation distortion is low, but not vanishingly so (the AK4452 was introduced in 2015), at 0.0024-0.0050% (re. 20Hz-20kHz, 0dBFs) falling to a minimum of 0.0009% over the top 20dB of its dynamic range [see Graph 1]. No detailed information is given about Onkyo's DIDRC (Dynamic Intermodulation Distortion Reduction Circuitry) but the trend of distortion vs. digital signal level is not as uniform as might be expected [black trace]. Jitter, too, is a complex mix of PSU and data-related sidebands [Graph 2] although its <500psec total (re. 48kHz-192kHz sample rates) is clearly very broadly spread. Otherwise, the 112dB A-wtd S/N ratio is generous and low-level resolution [red trace, Graph 1] good to a mere ±0.2dB error over a full 110dB dynamic range. PM