Rogue Audio 66LSR preamplifier Measurements part 2
Fig.4 Rogue 66LSR, distortion (%) vs output voltage at 1kHz into 100k ohms (top) and 10k ohms (bottom).
The distortion level was constant with frequency and consisted primarily of the sonically benign second harmonic (fig.5). This graph was taken at 1V into 10k ohms. At the same level into 100k ohms, the second harmonic rose to 0.1% (-60dB)—still sonically benign, but curious, to say the least. The intermodulation spectrum (fig.6) was dominated by the 1kHz difference product, though "dominated" is hardly the word for something at -63dB (0.07%).
Fig.5 Rogue 66LSR, spectrum of 50Hz sinewave, DC-1kHz, at 1V into 10k ohms (linear frequency scale).
Fig.6 Rogue 66LSR, HF intermodulation spectrum, DC-22kHz, 19+20kHz at 2V into 10k ohms (linear frequency scale).
Other than its poor channel balance, relatively high noise floor, grounding anomalies, and the peculiar fact that it was happier driving 10k ohms than 100k ohms, this little preamp offers acceptable measured performance.—John Atkinson