Rotel RSP-1572 Surround Sound Preamp/Processor Page 5

Bottom Line

That HDMI muting issue aside, my time with the RSP-1572 was mostly smooth sailing. It’s impossible to fault the Rotel pre-pro’s basic A/V performance, and its elegant simplicity should harmonize nicely with a certain type of buyer’s system plans. If you’re a performance-first, features-second type who logs as many hours on music playback as on TV and movies, you may very well number among them.

Test Bench


All data were obtained from various test DVDs using 16-bit dithered test signals, which set limits on measured distortion and noise performance. Reference input level is –20 dBFS; reference output 200 mV into 100 kohms. Volume setting for reference level was 85. 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.

  • Distortion ref. (THD+N, 1 kHz) 0.025%
  • Noise level (A-wtd): –74.9 dB
  • Excess noise (with sine tone)
    • 16-bit (EN16): 1.1 dB
  • Frequency response: 20 Hz to 20 kHz +0, –0.16 dB

Reference input and output level is 200 mV; volume setting for reference output level was 84.5.

  • Max Input/Output Level (1 kHz): 5.8v/9.2v
  • Distortion (THD+N, 1 kHz,): 0.02%
  • Noise level (A-wtd): –85.3 dB
  • Frequency response: <10 Hz to 200 kHz +0, –5.1 dB

Reference level is –20 dBFS for 200 mV output; all level trims at zero. Volume setting for reference level was -85.

  • Distortion at reference level: 0.02%
  • Linearity error (at –90 dBFS): 0.2 dB
  • Noise level (A-wtd): –74.8 dB with 96-kHz/24-bit signals: –80.7 dB
  • Excess noise (with/without sine tone)
    • 16-bit (EN16): 1.2/1.3 dB
    • quasi-20-bit (EN20): 14.9/15 dB
  • Noise modulation: 0.15 dB
  • Frequency response: <10 Hz to 20 kHz +0, –0.1 dB
    • with 96-kHz/24-bit signals: <10 Hz to 44 kHz +0, -0.8 dB

Measured results obtained with Dolby Digital test signals.

  • Subwoofer-output frequency response (crossover set to 80 Hz): nominally 24 dB/octave (21 dB/octave approx.) above –6-dB rolloff point of 80 Hz (12 dB/oct. for analog input)
  • High-pass-filter frequency response (crossover set to 80 Hz): nominally 24 dB/octave below -6-dB point of 80 Hz (12 dB/oct. for analog input)
  • Maximum unclipped subwoofer output (trim at 0): 6.8v
  • Subwoofer distortion (from 6-channel, 30-Hz, 0-dBFS signal; subwoofer trim set to 0): 0.6%
  • Crossover consistency: bass crossover frequency and slope were consistent for all sources and formats
  • Signal-format consistency: analog-signal crossovers ~12 dB/octave
  • Speaker size selection: all channels can be set to “small”
  • Speaker-distance compensation: available for all main channels.

I saw nothing on the test bench from Rotel’s RSP-1572 to contradict the superb sound I heard from music and movies alike. The pre-pro’s distortion and noise performance were consistently very good. Noise results fell less than a decibel short of the theoretical ideal on the 16-bit digital-signal tests, while analog-input noise improved on this by about 10 dB — good, but not great, performance. S/N for 96/24 PCM stereo signals bettered the 44.1/16 result by about 6 dB, a meaningful gain but also a few decibels shy of the best we’ve seen. Taken together, these suggest that analog-domain noise was the Rotel’s limiting factor, a phenomenon not uncommon among more “audiophile-oriented” designs where factors other than data-sheet specs often influence component selection. In any event, these figures suggest a real dynamic range of something over 100 dB, which, unless you listen in an anechoic chamber or over very fine headphones (and headphone amplification, as the RSP-1572 lacks a “cans” output), is plenty to spare.

One other note concerns the RSP-1572’s crossover-filter action. On digital signals, I found both high- and low-pass sides to show nominally 24-dB-per-octave slopes; the more usual arrangement is for the high-pass side to roll off at 12 dB per octave. With analog inputs, however, both sides displayed nominally 12-dB-per-octave slopes. The difference could conceivably effect a mild shift in bottom-octaves character between the two media, though on my system (which I cross over at a low 60 Hz), I noted no such thing.

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