Test Bench: Pioneer VSX-94TXH A/V Receiver
Pioneer's latest A/V receiver produced uniformly excellent bench results: linearity and S/N were close to perfect on both PCM and Dolby Digital signals, while distortion and frequency response were nearly as good (the latter, in particular, on 96/24 PCM). Noise levels were more average on 96/24, as well as on analog-multichannel tests, suggesting that analog-domain residuals were the limiting factor here.
Power output was generous in 2- and 1-channel tests, and the 94TXH was happy enough driving 4-ohm loads. With 5 and 7 channels driven, and its clamping circuitry in full effect, the receiver fell well short of 100 watts per channel, but was still better than some receivers of similar ratings we've seen, and in any event, this is of no real world consequence. Pioneer's protection system worked seamlessly by reducing effective power by about half when extended all-channel clipping excursions were imposed, and the receiver never really became unpleasantly hot.
High distortion (7.1%) detected in the subwoofer output when driven by a 6-channel, 30 Hz Dolby Digital signal was unusual and not caused by waveform clipping in the usual sense; a waveform monitor instead showed an odd squeeze-and-tilt effect that measures as distortion but which I would normally associate with a digital arithmetic error of some sort. Performance with 2-channel low frequency (PCM) signals was much better(2.5%) and with single-channel signals was on par with my fullband tests, i.e. below 0.1%. My conjecture is that there is an error in the summing routine that adds "small" channels' low-passed signals. Since, when playing actual program material, the odds of multiple channels ever demanding anything remotely close to 0 dBFS levels simultaneously (and in-phase) are exceedingly close to nil, I have no reservations about real-world performance. I certainly heard no audible anomalies in my listening tests.
DOLBY DIGITAL PERFORMANCE
All data were obtained from various test DVDs using 16-bit dithered test signals, which set limits on measured distorting and noise performance. Reference input level is -20 dBFS, and reference output is 1 watt into 8 ohms. Volume setting for reference level was -8. All level trims at zero, 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: 178/300 W (22.5/24.8 dBW) 5 channels driven (8 ohms): 84 W* (19.2 dBW) 7 channels driven (8 ohms): 61 W* (17.9 dBW) Distortion at 1 watt (THD+N, 1 kHz) 8/4 ohms: 0.05/0.06% Noise level (A-wtd): -75.1 dB Excess noise (with sine tone) 16-bit (EN16): 0.8 dB Frequency response: 20 Hz to 20 kHz +0, -0.2 dB *After approx. 10 seconds of continuous drive at these levels, protection circuits activated to reduce drive by 3 dB, i.e. half power; power-cycling the unit restored full drive.
MULTICHANNEL PERFORMANCE, ANALOG INPUT
Reference input and output level is 200 mV; volume setting for reference output level was -4. Distortion (THD+N, 1 kHz, 8 ohms): 0.04% Noise level (A-wtd.): -84.1 Frequency response: <10 Hz to 81 kHz +0, -3 dB
STEREO PERFORMANCE, DIGITAL INPUT
Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was -3.
Output at clipping (1 kHz, 8/4 ohms, both channels driven): 158/244 W (22.0/23.9 dBW) Distortion at reference level: 0.06% Linearity error (at -90 dBFS): 0.1 dB Noise level (A-wtd): -75.2 dB with 96-kHz/24-bit signals: -82.6 dB Excess noise (with/without sine tone) 16-bit (EN16): 0.5/0.7 dB quasi-20-bit (EN20): 13.0/12.6 dB Noise modulation: 0.8 dB Frequency response: <10 Hz to 20 kHz +0, -0.2 dB with 96-kHz/24-bit signals: <10 Hz to 45 kHz +0, -1.8 dB
Measured results obtained with Dolby Digital test signals. Subwoofer-output frequency response (crossover set to 80 Hz): 24 dB/octave (approx.) above -6-dB rolloff point of 80 Hz High-pass-filter frequency response (crossover set to 80 Hz): 12 dB/octave below -3-dB rolloff point of 80 Hz Maximum unclipped subwoofer output (trim at 0): 7.8v Subwoofer distortion (from 6-channel, 30-Hz, 0-dBFS signal; subwoofer trim set to 0): 7.1%** 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.