Mark Levinson No.334 power amplifier Measurements page 3

The No.334's THD+noise vs output power curves are shown in fig.7, while the discrete clipping levels are shown in Table 1. With the low AC line voltage, the amplifier doesn't quite meet its specified power into the lower impedances, though the shortfall is inconsequential. John Atkinson also measured the No.334's maximum output power using the Miller Audio Research Amplifier Profiler and a low-duty-cycle 1kHz toneburst to avoid loading down the AC line and the amplifier's power supply. The result is graphically shown in fig.8. Though with this signal and one channel driven, the amplifier did meet its specification into 4 ohms, there was still a very slight shortfall into the demanding 2 ohm and 1 ohm loads. Into these impedances, 492W and 829W were available, these powers equivalent to output currents of 15.7A and 28.8A, respectively. Note the very low levels of distortion in this graph, particularly into 8 and 4 ohms, up to the point where the amplifier starts to clip. There is then a relatively gradual rise to the 1% (-40dB) clipping point due to the No.334's soft-clipping circuit.

Fig.7 Mark Levinson No.334, distortion (%) vs continuous output power into (from bottom to top): 8 ohms, 4 ohms.

Fig.8 Mark Levinson No.334, distortion (%) vs burst output power into 8 ohms (black trace), 4 ohms (red), 2 ohms (blue), and 1 ohm (green).

With the exception of the unweighted noise floor, which should be inaudible, this is a solid set of measurements.—Thomas J. Norton

Table 1: Mark Levinson No.334 Continuous Clipping

(1% THD+noise at 1kHz)
Both Channels DrivenOne Channel Driven
Load ohms W (dBW)W (dBW)
  (L) (R) (L)
8 139.9 (21.46) 139 (21.43) 140 (21.46)
(line) 113V 114V 114V
4 243.4 (20.86) 239.5 (20.79) 260.8 (21.16)
(line) 112V 112V 114V
2 430 (20.33)  
(line) 112V  
8 ohms/bridged 486 (26.87)  
(line) 112V