Test Bench: Sony STR-DG910 A/V Receiver
DOLBY DIGITAL PERFORMANCE
All data were obtained using various test DVDs with 16-bit dithered test signals, which set limits on measured distortion and noise performance. Reference input level is -20 dBFS, and reference output is 1 watt into 8 ohms. Volume setting for reference level was 60. All level trims at zero, and except for subwoofer-related tests, all speakers were set to "large," subwoofer on. All are worst-case figures where applicable.
Output at clipping (1 kHz into 8/4 ohms) 1 channel driven: 84/138 watts (19.2/21.4 dBW) 5 channels driven (8 ohms): 30 watts (14.8 dBW)* Distortion at 1 watt (THD+N, 1 kHz, 8 or 4 ohms): 0.02% Noise level (A-weighted): -75.1 dB Excess noise (with sine tone) 16-bit (EN16): 1.2 dB Frequency response: 20 Hz to 20 kHz +0, -0.1 dB
*Multichannel tests, regardless of source signal (digital or analog, stereo or multichannel) or decoding modes, caused the STR-DG910 to limit output to about 30 watts or less per channel; see accompanying lab notes. Since the receiver lacks analog multichannel or preamp inputs, direct testing of power-amp channels was not possible.
STEREO PERFORMANCE, ANALOG INPUT
Reference input and output level is 200 millivolts; volume setting for reference output level was 61. Distortion (THD+N, 1 kHz, 8 ohms): 0.01% Noise level (A-weighted.): -89.2 dB Frequency response: 10 Hz to 200 kHz +0, -1.9 dB
STEREO PERFORMANCE, DIGITAL INPUT
Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was 60.
Output at clipping (1 kHz, 8/4 ohms, both channels driven): 75/109 watts (18.8/20.4 dBW) Distortion at reference level: 0.05% Linearity error (at -90 dBFS): 1 dB Noise level (A-weighted): -74.5 dB with 96-kHz/24-bit signals: -78.8 dB Excess noise (with/without sine tone) 16-bit (EN16): 0.25/0.35 dB quasi-20-bit (EN20): 14.7/14.8 dB Noise modulation: 0.6 dB Frequency response: 20 Hz to 20 kHz +0, -0.1 dB with 96-kHz/24-bit signals: 20 Hz to 43 kHz +0, -0.5 dB
Measured results obtained with Dolby Digital test signals. Subwoofer-output frequency response (crossover set to 80 Hz): 12 dB/octave above -6-dB rolloff point of 106 Hz (-3 dB at 80 Hz) High-pass-filter frequency response (crossover set to 80 Hz): 6 dB/octave below -3-dB rolloff point of 80 Hz Maximum unclipped subwoofer-output level (trim at 0): 4.7 volts Subwoofer-output distortion (from 6-channel, 30-Hz, 0-dBFS signal; subwoofer trim set to 0): 0.4% Crossover consistency: bass crossover frequency and slope were consistent for all sources and formats Signal-format consistency: consistent for all applicable formats Speaker size selection: all channels can be set to "small" Speaker-distance compensation: available for all main channels
The Sony STR-DG910 A/V receiver produced excellent numbers in most noise and distortion tests and impressive frequency response across the board. I noted the relatively shallow crossover-filter slopes (6/12 dB per octave, high-/low-pass) that Sony seems to use in its receivers. Half as steep as the de facto standard, these may affect subwoofer setup, positioning, and blending - not necessarily better or worse, but different.
Power measurements were a bit disappointing for a receiver that claims 100 watts per channel surround-mode power into 8 ohms. Stereo power was fairly typical for a mid-priced receiver, though 4-ohm wattage seemed slightly curtailed, probably by power-supply current capacity. But multichannel power results, at least in conventional steady-state tests, showed only about 30 watts per channel; I conjecture (but never received any confirmation or explanation from Sony) that the receiver's software deliberately limits steady-state power-supply current whenever any multichannel mode is invoked, either by the user or automatically (as by a Dolby Digital or DTS bit-flag). Still, although the receiver showed signs of strain when pushed to the most extreme limits, my listening tests did not fully reflect such restricted multichannel ability as the measurements imply. This suggests to me that the receiver has more power on tap for short-term demands, even when in its multichannel modes.