Amplifiers

The Bryston's frequency response, from the unbalanced (RCA) input to the speaker output, measured –0.04dB at 10 Hz, -0.00dB at 20 Hz, -0.07dB at 20 kHz, and

-0.51dB at 50 kHz. The frequency response from the balanced (XLR) input to the speaker output in both of its balanced modes (regular and +6dB) measured -0.03 dB at 10Hz, -0.00dB at 20 Hz, -0.25dB at 20kHz, and -1.33dB at 50kHz.

The amplifier's gain measured 29.6dB in unbalanced mode, 23.5dB in the regular balanced mode, and 29.5dB in +6 balanced mode. S/N ratio, A-weighted from 0Hz to 24kHz at 2.83V into 8ohm, was -109dB in unbalanced mode, -107dB in regular balanced mode, and -106.4dB in +6dB balanced mode.

The THD+noise at 2.83V into 8ohm was 0.004% at 20Hz, 0.004% at 1kHz, and 0.005% at 20kHz at the balanced input in regular balanced mode. Under the same conditions into 4ohm, THD+noise measured 0.008% at 20Hz, 0.008% at 1kHz, and 0.006% at 20kHz in the regular balanced mode.

Into an 8ohm load, the Powerpack 300 clipped (1% THD+noise) at 361W at 20Hz and 411W at 1kHz. Into a 4ohm load, it clipped at 470W at 20Hz and 495W at 1kHz. The 0.1% THD+noise level driving an 8ohm load was reached at 341.0W at 20kHz. Bryston's test of the measured unit (their data were provided to us with the review sample) was 344W under these conditions, a variance of only 1% between their number and ours.—TJN