Preamplifiers

Classe CP-800 Stereo Preamplifier

ARTICLE INDEX

The Classé CP-800 On the Bench

All distortion measurements were made within an 80 kHz bandwidth into 100 kOhms load. I used the XLR inputs for analog audio and the USB-F input (on the front panel) for my iPod.

At 1 kHz, 0 dB volume setting, 2 volts output, no DSP, distortion was a vanishing low 0.001%. This is pretty much inaudible and fantastic performance. Note that you can totally turn off the power to the digital circuits by disabling them in the setup menu, but I did not do this, because I wanted to see how the unit performs with everything powered up. The low distortion result, with the digital circuits powered but not being used, indicates that the digital circuits are well isolated from the analog circuitry.

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At 1 kHz, +8 dB volume setting (engages active preamplification, while 0 dB and below is passive), 5 volts output, no DSP, distortion was still very low.

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For this spectrum, I engaged the DSP by setting two EQ bands: one for the left channel, giving 100 Hz a 3 dB boost, and one for the right channel, giving a 3 dB attenuation. The volume control was set at 8. Distortion still remained below 0.01%, but it does show there is a price to pay for putting the signal through A/D and D/A.

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Using a combination of 19 kHz and 20 kHz sine waves, the B-A peak at 1 kHz was 120 dB below the fundamentals, which is superb.

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IMD was in line with the other measurements, at only 0.001%. IMD is an extremely important measurement, because a low amount - and it is very low with the CP-800 - means you will hear more detail.

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THD+N vs. Voltage Output indicates a robust power supply, as you can see. Even with a tortuous load of 600 ohms, the sharp knee was at 9 volts output. Keep in mind that you will only be using about 2 volts or so of output voltage. The rest is overhead, meaning a good dynamic range.

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The measured Frequency Response was 10 Hz - 200 kHz, - 1 dB.

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