Pre/Power Amplifiers

With the LECUTA volume cranked fully clockwise, maximum gain is +15.1dB (XLR in/out) with a channel imbalance of 0.12dB at +6dB gain. Maximum output is a substantial 19.5V with distortion increasing steadily with level from 0.0025%/100mV to 0.014%/1V and 0.15%/10V. This holds true from 100Hz-10kHz but THD increases marginally at higher frequencies (0.032%/1V/20kHz) and more obviously so at very low frequencies to 0.08%/20Hz and 0.9%/5Hz. This is more likely a function of the input and output coupling transformers than the dual-mono E88CC tube line stage [see Graph 2, below]. The triode stage is also very quiet, revealing an A-wtd S/N ratio of 100dB (re. 0dBV) and a residual noise of just –97dBV (14µV). The response is extended, showing a lift in the ultrasonic to +1.7dB/100kHz but, more worrisome for vinyl sources, a +12dB spike at 3Hz. The low cut filter [dotted trace, Graph 1] is mandatory for LP-based systems.

The CL-1000 has a versatile MM/MC phono stage even if the gain is not exactly as advertised! In practice the '+38dB MM' input is closer to +54dB while the +57dB and +66dB MC options (40/10ohm loading, respectively) are closer to +73dB and +76.5dB. This means the CL-1000 is rather better suited to low-output MMs and MCs than you might suspect, without there being a trade-off in either the input overload margins or S/N ratios. In MM guise the CL-1000 has a sensitivity of 2.1mV with a generous limit of 90mV (32.6dB headroom) and a wide 86.2dB A-wtd S/N ratio. For MC (low/medium and high gain) the figures are 225µV and 150µV for sensitivity with overload limits of 10.5mV and 7.5mV, and 73.6dB/67.0dB for the S/N. Clearly 'MC Low or Med' are the settings to choose for 95% of likely MCs. PM