Classé Omega power amplifier:
Measurements
Measurements
Unless otherwise noted, the measurements here were taken in the Classé Omega's unbalanced mode.

Following its 60-minute, 1/3-power preconditioning test, the Omega's heatsinks were barely warm. The amplifier's input impedance measured 129k ohms in the unbalanced mode, but considerably lower—8.4k ohms—in the balanced configuration. The output impedance is a very low 0.03 ohms at 1kHz, rising to a maximum of 0.036 ohms at 20kHz with a 4 ohm load.

The voltage gain into 8 ohms was 29.3dB (virtually the same in the balanced mode). The amplifier is noninverting at its unbalanced inputs, and pin 2 of the balanced input is positive. Its S/N ratio measured 87.2dB from 22Hz to 22kHz unweighted, 76.6dB from 10Hz to 500kHz unweighted, and 89.3dB A-weighted (all referenced to 1W into 8 ohms). DC offset measured a low 4mV in the left channel, 1.9mV in the right.

The Classé's small-signal frequency response is plotted in fig.1. The balanced response measured within 0.05dB of the unbalanced and is not shown here. The very low output impedance means that any changes in response with our simulated loudspeaker load are negligible. The 10kHz squarewave response (fig.2) has a very short risetime, with only a slight rounding at the leading edges associated with the falling response above 20kHz. The 1kHz response, not shown, is practically a textbook squarewave. The crosstalk measurements shown in fig.3 are fine, the HF increase due, as is usual, to capacitive interchannel coupling.

Fig.1 Classé Omega, unbalanced frequency response at (from top to bottom at 6kHz): 1W into 8 ohms, 2W into 4 ohms, and 2.828V into simulated loudspeaker load (right channel dashed, 0.5dB/vertical div.).

Fig.2 Classé Omega, small-signal 10kHz squarewave into 8 ohms.

Fig.3 Classé Omega, Crosstalk (from top to bottom at 30kHz): R-L, balanced, unbalanced; L-R unbalanced, balanced (10dB/vertical div.).