RMAA Testing the OPPO BDP-83


This article presents results for RMAA (RightMark Audio Analyzer) testing of the OPPO BDP-83 Blue-ray disc player. Tests are reported only for the stereo analog line-out connection using test signals with 24 bit resolution at a sampling frequency of 96 kHz. The impressive results shown here indicate good audio layout in design for a product that has received consistently very good reviews.

The following tests were performed:

Testing Methodology


The Creative X-Fi Elite Pro sound card was used for the RMAA tests using the main line-in on the sound card. To create the test wav files, a DVD-Audio disc was created using WaveLab 6. Since the BDP-83 has good support for DVD-Audio playback with menu navigation this is a convenient test approach. The test disc contains 3 groups with test tracks at various frequencies including the RMAA-generated test and calibration wav files. The single-tone test wave files were created with the GenWav6 utility. The groups have wave data at 16 bit/44.1 kHz, 24 bit/96kHz and 24 bit/48 kHz 5.1 respectively. For the tests reported here, only the 24 bit 96 kHz test group was used. The DVD-Audio track navigation menu for this group is shown below as seen on an external video display:





The stereo output of the BDP-83 was connected to the line-in of the X-Fi Elite Pro sound card using a high-quality stereo cable. RMAA was run and configured for 24 bit 96 kHz analysis. For the "spot" spectral checks, RMAA was used to monitor the incoming signal which was adjusted to -1 dBFS. The X-Fi Elite Pro was set at 0 dB input recording gain with all channels and outputs muted for these stop checks. For the full RMAA tests, the RMAA calibration signal track was played back via the BDP-83 and the output level of the BDP-83 was adjusted slightly to obtain a line-in monitor signal level of -1 dBFS. Then RMAA was "record armed" and the RMAA test track was played back while RMAA "recorded" the result and performed analysis. To check the limitations imposed by the X-Fi Elite Pro sound card, a direct "loop back" RMAA test was performed with the sound card line-out connected directly to the sound card line-in using the same audio cable and connectors. The details of the procedure are as described in Creative's X-Fi Testing Methodology .

Results


With a 0dBFS (100 digital signal) 24 bit/96 kHz sine wave track played back at 1 kHz, the BDP-83 output voltage measured directly on a calibrated oscilloscope was:
     Vp = 3.4 V    or Vrms = 2.4 Vrms    or 7.6 dBV    or 9.8 dBu

To check background noise, the stereo cable was first connected to a shielded box with terminations of 1 kohm on each channel at the connectors. This represents the noise background on the input of the X-Fi Elite Pro sound card in combination with the cable. This demonstrates the extremely low noise level over the entire audio spectrum with only a hint of an artifact at 25 kHz:



Next, the BDP-83 was connected, turned on and placed in pause mode. The noise results below show that, except for the artifact at ~ 16 kHz (and its harmonic) and a very slight rise from 10kHz to 30 kHz, the noise level is at the noise floor of the measurement sound card:



Next, a spot check using a 1 kHz sine wave signal at -1 dBFS was performed to check harmonic distortion content. First a home-made ultra-low distortion Wien-bridge oscillator was used and attached directly to the sound-card line-in. This oscillator circuit uses the LM4562NA opamp which has exceptionally low THD. The visible first and second harmonics are due to the X-Fi Elite pro sound card:



Then a -1 dBFS test wave file was played back with the BDP-83 connected. Both channels are shown here. The spectrum shows a rise in the noise level beyond 5 kHz with the test signal applied. However the noise level is still extremely low:



Full RMAA Test Results


The full RMAA test results compare the performance of the BDP-83 dedicated stereo line-out and analog multichannel FL/FR line-out using the Creative Technologies X-Fi Elite Pro reference sound card for spectrum analysis. For the multichannel FL/FR outputs, the surround configuration was set at Stereo with speaker setting at LARGE (which suppresses the 80 Hz low frequency roll-off that would be used in a typical 5.1 speaker surround setup with a subwoofer). The frequency response of the dedicated stereo line-out and the multichannel analog output of the BDP-83 are similar with a slight peaking for the multichannel line-out. Both responses extend to over 40 kHz. A 40 kHz bandwidth is of course expected for a 96 kHz sampling rate assuming that an output bandwidth rolloff filter isn't part of the design. However, OPPO's specification for frequency response only indicates "20Hz - 20 kHz +/- 0.4 dB". Summary results of the full RMAA test of the BDP-83 compared to the loop-back test (which indicates the limitations of the sound card capabilities) are summarized below:



The BDP-83 specifications are S/N > 110 dB A and THD + N < 0.002%. The RMAA results reported here are consistent with the specifications for both the dedicated stereo and surround analog outputs. The noise level and dynamic range are both about 1.5 dB poorer for the FL/FR surround analog outputs compared to the dedicated stereo analog outputs but are still very low and would provide excellent analog-output performance when used with any high-quality surround analog receiver/amplifier. Since the BDP-83 uses a higher performance DAC for the stereo line-out circuit (the Cirrus Logic CS4398) compared to the 7.1 analog outputs which uses the Cirrus Logic CS4382, somewhat lower performance is expected from the surround analog outputs.

References