Fig.6 Audio Research Reference Two, balanced HF intermodulation spectrum, DC-22kHz, 19+20kHz at 2V into 100k ohms (linear frequency scale).
Finally, the Reference Two can output very high levels of low-distortion signal into high impedances. Fig.7 shows the THD+noise percentage plotted against balanced output voltage into 100k ohms (bottom trace) and 600 ohms (top trace). The preamplifier doesn't clip (…