Hello to everyone.
This is a review and test of the Sony DVP-S9000ES DVD-V, SACD and CD player. It was released at the end of 2000 and cost about $1,500.
Presentation
The Sony DVP-S9000ES is primarily a DVD-V player only capable of multichannel audio output through digital S/PDIF or optical Toslink output. Is has no Dolby Digital (except for down-mixing surround sound in stereo for the digital outputs) or DTS decoding capability. On the analogue side, it only has stereo outputs (two in parallel). Besides DVD-V, it is able to play CD Audio and, above all, SACD (only their stereo content though, without any possibility to access to multichannel content due to the lack of digital output for DSD data).
This player belongs to the very first generation of SACD players from Sony, which was introduced with the SCD-1 in 1999. It uses Sony's own "Pulse Length Modulation" (PLM) digital to analogue conversion system. I described this system at length and the way it handles both PCM data and DSD data in my review of the Sony SCD-555ES, so I invite you to read it if you want to understand the technical aspects of the digital to analogue conversion with both types of digital signal. The only difference with the SCD-555ES (and, by the way, the SCD-1 et SCD-777ES) is that the DVP-S9000ES uses a integrated digital processor and DAC chip, the Sony CXD9556, instead of separate processor and DAC.
You may have noticed on the above pictures that the fit and finish of this player is lavish and that the built quality is of a very high standard. You can easily find pictures of the inside of this player on the Internet to see for yourself that the internal build quality is just as impressive as the external appearance. This is truly a high-end item.
Let's move on to the review !
I will do my best to adhere to the following general framework, when it is possible with the various test discs available to me:
1. Dashboard @ about 1 kHz, 0 dBFS
2. Frequency response related measurements
3. Noise and distortion related measurements
4. Linearity tests
5. Special tests
6. Disc readability tests
Concerning test discs, I believe I have the opportunity to inaugurate the new NTTY's pressed CD TEST. @NTTY deserves our warmest thanks for creating this remarkable testing tool!
This review will be divided in four parts.
In this opening post:
- Part 1: CD player measurements (PCM 16 bits @ 44.1 ksps);
In post #2:
- Part 2: DVD-V player measurements (PCM 24 bits @ 48 and 96 ksps);
- Part 3: SACD player measurements (DSD);
- Part 4: Comparison between the CD, DVD and SACD formats.
Part 1: Measurements of the Sony DVP-S9000ES as a CD Player
All measurements were taken with an Audio Precision System One+DSP SYS222A. Unless otherwise stated, the tests were performed with NTTY's Audio Technical CD. The Audio Precision was always been given the 30 minutes preconditioning period mandated in its calibration procedure and the device under test the 5 minutes mandated by the AES-17 standard.
a. Dashboards
The DVP-S9000ES gets two interpolation filters to choose from, designated #1 and #2. They can only be selected through the on-screen display menu. Unless otherwise noted, all measurements below are performed with the standard digital filter, ie. #1.
Keep in mind that the old Audio Precision System One has no dual analogue to digital converter per analyzer channel, hence cannot display a recombined representation of both the test signal and the distortion residual. Contrary to @amirm's reviews, you will only see the distortion residual with a “notch” on each side of the leftover of the test signal: this is where the analyzer band-reject filter has removed the test tone prior to the digitization and measurement of the residual signal.
The output level is in the vicinity of 2.3 V RMS. The levels of the two channels are very closely matched to within 0.04 dB.
Despite the presence of very low level power supply hum and slight high frequency spurious tones, the SINAD is noise-dominated.
Dashboards with the digital filter #2 (not shown) are almost identical, save for a slight decrease in the high frequency noise floor due to the earlier -3 dB roll-off point.
More interesting is to show a dashboard when a -6 dB digital attenuator is enable. It should be noted that plugging an old cathode ray tube monitor in one of the SCART video output slightly increases visible hum level notably around 50 Hz. Using the "Audio Direct" feature accessible through a front panel button or the remote control unit defeats the video output and almost all the additional hum noise. Overall, the effects of the monitor on hum level is really nothing to worry about.
I show the left channel only, because the only thing worth to notice is that we unsurprisingly loose about 1 bit of resolution due to the attenuated level. The THD decreases slightly.
To comply with the practice set by NTTY in his exceptionally thorough CD player reviews, here are dashboards of the two channels configured the same but at -6 dBFS (with the digital attenuator disable):
At -6 dBFS, the respective THD+N (inverse of SINAD) of the two channels are almost the same and are noise dominated, although the THD part decreases. The channels matching does not change.
b. Frequency response
Let's see how the two available interpolation filters of the Sony act on the player’s frequency response:
There is no difference in the output level, which is a good point, but the digital filter #2 is obviously a slow roll off type that restricts the high frequency bandwidth. There is no significant deviation of phase response between the two channels with either of the digital filters.
Another way to look at the effect of the digital filters is to trace the wideband response with white noise up to ultrasonic frequencies (in this case 85 kHz):
By comparing this graph to the equivalent one in the SCD-555ES review, we can see that Sony only provided one alternate filter out of the 4 available in its processor and that it is the filter named "Clear" in the SCD-555ES.
The DVP-S9000ES decodes emphasized tones at -20 dBFS from the Stereophile Test CD2 at almost correct levels:
Crosstalk evaluated with spot tones from the Denon Audio Technical CD is significantly different in the right to left than the left to right direction, but is very good good in both cases:
c. Noise and distortion measurements
Let's start with some Left/Right single point measurements about noise and distortion before proceeding with more graphs. All measurements were performed with standard Audio Precision tests.
The huge signal to noise ratio indicates that when it is fed with a digital signal containing only “Infinity Zero” signal, the DAC mutes its output. Therefore, dynamic range and quantization noise give a more realistic picture of the performance of the player with 16 bits contents.
Notable is the frequency accuracy, which is the best I have measured so far. This is all the more significant that the player is 26 years old and that close examination of its schematics shows that it employs two crystal clocks, one for 44.1 ksps based system (CD, SACD), the other for 48 ksps based system (DVD), that are selected depending on the disc type loaded in the tray, but without shutdown of the unused crystal.
The default digital filter has no headroom to reproduce inter-sample overs. Neither has filter #2 (not shown). But when the -6 dB digital attenuator is enable, the picture is different and the DVP-S9000ES has perfect headroom to reproduce intersample overs up to + 3.01 dBFS. Of course, for this you must accept a loss of resolution of almost one full bit (6 dB) as shown on the dashboard above. So, now is time for a comparison table alla NTTY showing the average performances of all the CD players I have measured so far. You can access to the relevant review, when available, by clicking on the highlighted device name:
Note :
[1] Due to the very aggressive noise-shaping of the Cirrus Logic CS4392 DAC's 5th order sigma-delta modulator the Marantz uses, the measurement bandwidth was restricted to 22 Hz - 30 kHz in order to exclude as much noise as possible.
To go further in the noise analysis, Audio Precision provides some standard tests to assess the performance of a CD player.
First test is to look at the FFT spectrum of an “Infinity Zero” signal from the Denon Audio Technical CD up to 80 kHz:
As the DAC is muted, this graph only shows the player's analogue circuitry noise floor. A slight hum can be seen, as well as extremely low level high frequency spurious tones of unknown origin. The hum must be related to the internal signal routing and circuit board design. A variation of this test suggested by Audio Precision is to restrict the measurement bandwidth to the low frequencies and to lower the sample rate in order to narrow the bin frequency width. That way, it is possible to see mains frequency interference and power supply related noise with greater resolution:
Notwithstanding hum components, the very low base noise floor that is flat down to very low frequencies should be pointed out. Bear in mind, however, that when the DAC is active, the base noise floor would be higher, up to the level of the quantization noise of 16 bits signals (more on that in Part 4 below). When I performed a test similar to those carried out by NTTY at 0 dBFS looking for spurious power supply tones (not shown), the level of the hum did not change at such a high output level.
Another test uses the analogue analyzer to plot 1/3 octave curves of the noise with the same "Infinity Zero" signal. Although this method has less frequency resolution than the FFT analysis (the higher the frequency, the wider the noise bandwidth that each point of the curve represents contrary to an FFT analysis where each “bin” has equal bandwidth - that is why the curve obtained with the analogue analyzer regularly increases towards higher frequencies), it takes advantage of the greater dynamic range and the wider frequency response of the Audio Precision System One’s analogue analyzer over its ADCs.
Let's move on to distortion. THD+N vs frequency was evaluated with spot tones at 0 dBFS without dither from the Pierre Vérany Digital Test CD. First within a 20 kHz bandwidth (i.e. the audio band):
There is no increase in distortion in the bass, neither in the high frequencies, which is a good performance. The sharp downward slope of the curves above 10 kHz is due to the fact that the second harmonic at 10 kHz and above falls outside the pass-band of the test, hence there is no longer any harmonic to measure, only noise. The upward curves from about 15 kHz most probably indicates an increase in the noise (including quantization noise) or distortion due to imaging above the 22.05 kHz Nyquist frequency of CD folding back into the audio band when the player has to reproduce high frequencies at high level.
Second, here is the same test, but with a wider measurement bandwidth up to 80 kHz:
The curves are obviously dominated by broadband noise. Harmonic distortion takes over only with test frequencies above 5 kHz. Again, this is good performance.
THD+N in function of levels was also evaluated with the help the 999.91 Hz test signals from NTTY CD test disc. First with dithered tones (which gives a typical performance curve, because CD production is almost universally done with dither), and then with undithered tones (to see a truer picture of the level of performance of the player):
In both cases, the curves remain almost flat up to 0 dBFS, which shows that the THD+N is dominated by the dither noise or quantization noise, not distortion. That means that the DVP-S9000ES indeed produces very little harmonic distortion. This is compliant with distortion analysis from measurements made elsewhere that I have reported in this thread, where we learn that the Sony is one of the lowest distortion CD players ever tested. Nevertheless, the Sony DVP-S9000ES is not fully capable of 16 bits accuracy (-98 dB or so) due to its noise level, presumably the low frequency hum.
As the single point measurements showed, not only is the harmonic distortion very low, but intermodulation distortion also. Audio Precision's standard test to evaluate more qualitatively the SMPTE intermodulation distortion by looking at the digitization of the output of the analogue analyzer filter that removes the 60 Hz and 7 kHz tones to observe the actual distortion products confirms those numbers:
FFT of a -3.02 dBFS twin tones in a 23 kHz bandwidth shows very low even order distortion product (1 kHz) and sidebands as well:
The digital filter #2 lets some ultrasonic images of the twin tones bleed, but the in-band performance remains at least the same as with the digital filter #1 shown above:
The old 16 bits Burr Brown PCM78 ADCs of the Audio Precision System One probably limits the usefulness of an FFT of the multitone signal from NTTY's test CD. Moreover, the maximum FFT length that the System One is capable of restricts the bin frequency resolution in the bass. Anyway, here is the FFT spectrum of such signal, but from 100 Hz only:
d. Linearity Tests
I am happy to report that NTTY's pressed test CD from a glass master seems to ease linearity measurements with the Audio Precision System One. I wonder if the CD-R I used to use increases noise in the servo of the drive mechanism due to less than optimal reflectivity or other reading issues, which would impact the steadiness of the test signal. Anyway, both channels of the analyzer can now settle on readings down to very low levels:
I used the same scale than Amirm's for its own tests to ease comparison. The level at which the player's output deviates significantly from linearity lies somewhere between -110 dBFS and -120 dBFS. It is possible that the low level hum modulates the level of the test tone at the lowest level.
Here is an FFT analysis of the lowest level -130 dBFS sine signals:
Taking into account the averaging effect, the level of the test tone is shy of roughly 1 dB 'only' from the correct level.
e. Special Tests
Here is a capture of the waveform of a 997 Hz sine at -90.31 dBFS without dither from NTTY Test CD:
The three expected discrete voltage steps are clearly visible.
The Sony DAC is perfectly monotonic, i.e. increasing digital codes produce consistently increasing analogue outputs at the lowest levels. Most probably this characteristic is no longer difficult to get nowadays, but still:
Non-monotonic DAC can also be revealed by another special test which was proposed by Audio Precision in 1991 to check the absence of modulation of the noise floor of D/A converters at different levels (Richard C. Cabot, Noise Modulation in Digital Audio Equipment, AES preprint 3021). This test consists of accumulating on the same graph a third octave analysis of the quantization noise after the removal of a low frequency test signal at different levels from -50 to -100 dBFS. Any change on the shape of the noise floor would signal a modulation of this noise in function of level. Audio Precision quoted experiments previously conducted at Dolby Laboratories that had shown that noise modulation of as little as 2 dB may be audible. Nowadays, this test may have no longer relevance with modern D/A converters, especially sigma-delta converters, but maybe it can still be useful to check ladder type converters. Here is a modern take on this test by accumulating FFT spectra of the different test signal levels:
There is no visible modulation of the noise floor.
Finally, I used special dithered signals made by NTTY on the model of the Pierre Vérany Digital Test CD, which contains unique (non-dithered) tracks to perform a peculiar test called "intermodulation by crosstalk". The theory of operation of this test is as follows: the channel under test plays a 5 kHz tone and the other channel simultaneously plays a 1 kHz tone, both at 0 dBFS. If there is a significant crosstalk between channels, the 1 kHz tone can theoretically intermodulate with the 5 kHz tone to produce on the channel under test a difference frequency of 4 kHz and/or side-bands at 4 and 6 kHz due to amplitude modulation of the 5 kHz tone by the 1 kHz crosstalk tone. This test was designed at a time when most CD players have only a single digital to analogue converter for two channels for cost-savings reason. These CD players had to demultiplexe the left channel from the right by routing the output of the single DAC alternatively to each one of the two channels at twice the CD sampling frequency.
There is only very low level of intermodulation by crosstalk in the right channel. After compensating the effect of the notch filter, the IMD products lie at less than -120 dB under the test tone.
f. Disc Readability
To end the first part of this review dedicated to CD replay, I have used the famous Pierre Vérany Digital Test CD2 to check the ability of the Sony DVP-S9000ES to play damaged discs or disc pressings that are not compliant to the Red Book (RB) specifications. The criteria of failure on a test is either glitches, warping of the output waveform or an increase of THD+N from the nominal value. As NTTY obviously uses the same disc to perform its own tests, I will borrow his table:
(To be continued in message #2)
This is a review and test of the Sony DVP-S9000ES DVD-V, SACD and CD player. It was released at the end of 2000 and cost about $1,500.
Presentation
The Sony DVP-S9000ES is primarily a DVD-V player only capable of multichannel audio output through digital S/PDIF or optical Toslink output. Is has no Dolby Digital (except for down-mixing surround sound in stereo for the digital outputs) or DTS decoding capability. On the analogue side, it only has stereo outputs (two in parallel). Besides DVD-V, it is able to play CD Audio and, above all, SACD (only their stereo content though, without any possibility to access to multichannel content due to the lack of digital output for DSD data).
This player belongs to the very first generation of SACD players from Sony, which was introduced with the SCD-1 in 1999. It uses Sony's own "Pulse Length Modulation" (PLM) digital to analogue conversion system. I described this system at length and the way it handles both PCM data and DSD data in my review of the Sony SCD-555ES, so I invite you to read it if you want to understand the technical aspects of the digital to analogue conversion with both types of digital signal. The only difference with the SCD-555ES (and, by the way, the SCD-1 et SCD-777ES) is that the DVP-S9000ES uses a integrated digital processor and DAC chip, the Sony CXD9556, instead of separate processor and DAC.
You may have noticed on the above pictures that the fit and finish of this player is lavish and that the built quality is of a very high standard. You can easily find pictures of the inside of this player on the Internet to see for yourself that the internal build quality is just as impressive as the external appearance. This is truly a high-end item.
Let's move on to the review !
I will do my best to adhere to the following general framework, when it is possible with the various test discs available to me:
1. Dashboard @ about 1 kHz, 0 dBFS
2. Frequency response related measurements
3. Noise and distortion related measurements
4. Linearity tests
5. Special tests
6. Disc readability tests
Concerning test discs, I believe I have the opportunity to inaugurate the new NTTY's pressed CD TEST. @NTTY deserves our warmest thanks for creating this remarkable testing tool!
This review will be divided in four parts.
In this opening post:
- Part 1: CD player measurements (PCM 16 bits @ 44.1 ksps);
In post #2:
- Part 2: DVD-V player measurements (PCM 24 bits @ 48 and 96 ksps);
- Part 3: SACD player measurements (DSD);
- Part 4: Comparison between the CD, DVD and SACD formats.
Part 1: Measurements of the Sony DVP-S9000ES as a CD Player
All measurements were taken with an Audio Precision System One+DSP SYS222A. Unless otherwise stated, the tests were performed with NTTY's Audio Technical CD. The Audio Precision was always been given the 30 minutes preconditioning period mandated in its calibration procedure and the device under test the 5 minutes mandated by the AES-17 standard.
a. Dashboards
The DVP-S9000ES gets two interpolation filters to choose from, designated #1 and #2. They can only be selected through the on-screen display menu. Unless otherwise noted, all measurements below are performed with the standard digital filter, ie. #1.
Keep in mind that the old Audio Precision System One has no dual analogue to digital converter per analyzer channel, hence cannot display a recombined representation of both the test signal and the distortion residual. Contrary to @amirm's reviews, you will only see the distortion residual with a “notch” on each side of the leftover of the test signal: this is where the analyzer band-reject filter has removed the test tone prior to the digitization and measurement of the residual signal.
The output level is in the vicinity of 2.3 V RMS. The levels of the two channels are very closely matched to within 0.04 dB.
Despite the presence of very low level power supply hum and slight high frequency spurious tones, the SINAD is noise-dominated.
Dashboards with the digital filter #2 (not shown) are almost identical, save for a slight decrease in the high frequency noise floor due to the earlier -3 dB roll-off point.
More interesting is to show a dashboard when a -6 dB digital attenuator is enable. It should be noted that plugging an old cathode ray tube monitor in one of the SCART video output slightly increases visible hum level notably around 50 Hz. Using the "Audio Direct" feature accessible through a front panel button or the remote control unit defeats the video output and almost all the additional hum noise. Overall, the effects of the monitor on hum level is really nothing to worry about.
I show the left channel only, because the only thing worth to notice is that we unsurprisingly loose about 1 bit of resolution due to the attenuated level. The THD decreases slightly.
To comply with the practice set by NTTY in his exceptionally thorough CD player reviews, here are dashboards of the two channels configured the same but at -6 dBFS (with the digital attenuator disable):
At -6 dBFS, the respective THD+N (inverse of SINAD) of the two channels are almost the same and are noise dominated, although the THD part decreases. The channels matching does not change.
b. Frequency response
Let's see how the two available interpolation filters of the Sony act on the player’s frequency response:
There is no difference in the output level, which is a good point, but the digital filter #2 is obviously a slow roll off type that restricts the high frequency bandwidth. There is no significant deviation of phase response between the two channels with either of the digital filters.
Another way to look at the effect of the digital filters is to trace the wideband response with white noise up to ultrasonic frequencies (in this case 85 kHz):
By comparing this graph to the equivalent one in the SCD-555ES review, we can see that Sony only provided one alternate filter out of the 4 available in its processor and that it is the filter named "Clear" in the SCD-555ES.
The DVP-S9000ES decodes emphasized tones at -20 dBFS from the Stereophile Test CD2 at almost correct levels:
Crosstalk evaluated with spot tones from the Denon Audio Technical CD is significantly different in the right to left than the left to right direction, but is very good good in both cases:
c. Noise and distortion measurements
Let's start with some Left/Right single point measurements about noise and distortion before proceeding with more graphs. All measurements were performed with standard Audio Precision tests.
The huge signal to noise ratio indicates that when it is fed with a digital signal containing only “Infinity Zero” signal, the DAC mutes its output. Therefore, dynamic range and quantization noise give a more realistic picture of the performance of the player with 16 bits contents.
Notable is the frequency accuracy, which is the best I have measured so far. This is all the more significant that the player is 26 years old and that close examination of its schematics shows that it employs two crystal clocks, one for 44.1 ksps based system (CD, SACD), the other for 48 ksps based system (DVD), that are selected depending on the disc type loaded in the tray, but without shutdown of the unused crystal.
The default digital filter has no headroom to reproduce inter-sample overs. Neither has filter #2 (not shown). But when the -6 dB digital attenuator is enable, the picture is different and the DVP-S9000ES has perfect headroom to reproduce intersample overs up to + 3.01 dBFS. Of course, for this you must accept a loss of resolution of almost one full bit (6 dB) as shown on the dashboard above. So, now is time for a comparison table alla NTTY showing the average performances of all the CD players I have measured so far. You can access to the relevant review, when available, by clicking on the highlighted device name:
| Intersample-overs tests Bandwidth of the THD+N measurements is 22Hz - 80kHz | 5512.5 Hz sine, Peak = +0.69 dBFS | 7350 Hz sine, Peak = +1.25 dBFS | 11025 Hz sine, Peak = +3.01 dBFS | Headroom |
|---|---|---|---|---|
| Sony SCD-XA9000ES | -92.1 dB | -93.4 dB | -86.2 dB | +3.01 dB |
| Sony DVP-S9000ES (-6dB output) | -81 dB | -81.5 dB | -82.6 dB | +3.01 dB |
| Marantz DV-12S2 [1] | -76.7 dB | -76.7 dB | -32.4 dB | +2.01 dB |
| Pioneer DV-868AVi | -30.2 dB | -24.7 dB | -17.6 db | none |
| Sony SCD-555ES | -30.2 dB | -24.4 dB | -16.4 dB | none |
| Sony DVP-S9000ES (0 dB output) | -29.8 dB | -24.1 dB | -16.1 dB | none |
[1] Due to the very aggressive noise-shaping of the Cirrus Logic CS4392 DAC's 5th order sigma-delta modulator the Marantz uses, the measurement bandwidth was restricted to 22 Hz - 30 kHz in order to exclude as much noise as possible.
To go further in the noise analysis, Audio Precision provides some standard tests to assess the performance of a CD player.
First test is to look at the FFT spectrum of an “Infinity Zero” signal from the Denon Audio Technical CD up to 80 kHz:
As the DAC is muted, this graph only shows the player's analogue circuitry noise floor. A slight hum can be seen, as well as extremely low level high frequency spurious tones of unknown origin. The hum must be related to the internal signal routing and circuit board design. A variation of this test suggested by Audio Precision is to restrict the measurement bandwidth to the low frequencies and to lower the sample rate in order to narrow the bin frequency width. That way, it is possible to see mains frequency interference and power supply related noise with greater resolution:
Notwithstanding hum components, the very low base noise floor that is flat down to very low frequencies should be pointed out. Bear in mind, however, that when the DAC is active, the base noise floor would be higher, up to the level of the quantization noise of 16 bits signals (more on that in Part 4 below). When I performed a test similar to those carried out by NTTY at 0 dBFS looking for spurious power supply tones (not shown), the level of the hum did not change at such a high output level.
Another test uses the analogue analyzer to plot 1/3 octave curves of the noise with the same "Infinity Zero" signal. Although this method has less frequency resolution than the FFT analysis (the higher the frequency, the wider the noise bandwidth that each point of the curve represents contrary to an FFT analysis where each “bin” has equal bandwidth - that is why the curve obtained with the analogue analyzer regularly increases towards higher frequencies), it takes advantage of the greater dynamic range and the wider frequency response of the Audio Precision System One’s analogue analyzer over its ADCs.
Let's move on to distortion. THD+N vs frequency was evaluated with spot tones at 0 dBFS without dither from the Pierre Vérany Digital Test CD. First within a 20 kHz bandwidth (i.e. the audio band):
There is no increase in distortion in the bass, neither in the high frequencies, which is a good performance. The sharp downward slope of the curves above 10 kHz is due to the fact that the second harmonic at 10 kHz and above falls outside the pass-band of the test, hence there is no longer any harmonic to measure, only noise. The upward curves from about 15 kHz most probably indicates an increase in the noise (including quantization noise) or distortion due to imaging above the 22.05 kHz Nyquist frequency of CD folding back into the audio band when the player has to reproduce high frequencies at high level.
Second, here is the same test, but with a wider measurement bandwidth up to 80 kHz:
The curves are obviously dominated by broadband noise. Harmonic distortion takes over only with test frequencies above 5 kHz. Again, this is good performance.
THD+N in function of levels was also evaluated with the help the 999.91 Hz test signals from NTTY CD test disc. First with dithered tones (which gives a typical performance curve, because CD production is almost universally done with dither), and then with undithered tones (to see a truer picture of the level of performance of the player):
In both cases, the curves remain almost flat up to 0 dBFS, which shows that the THD+N is dominated by the dither noise or quantization noise, not distortion. That means that the DVP-S9000ES indeed produces very little harmonic distortion. This is compliant with distortion analysis from measurements made elsewhere that I have reported in this thread, where we learn that the Sony is one of the lowest distortion CD players ever tested. Nevertheless, the Sony DVP-S9000ES is not fully capable of 16 bits accuracy (-98 dB or so) due to its noise level, presumably the low frequency hum.
As the single point measurements showed, not only is the harmonic distortion very low, but intermodulation distortion also. Audio Precision's standard test to evaluate more qualitatively the SMPTE intermodulation distortion by looking at the digitization of the output of the analogue analyzer filter that removes the 60 Hz and 7 kHz tones to observe the actual distortion products confirms those numbers:
FFT of a -3.02 dBFS twin tones in a 23 kHz bandwidth shows very low even order distortion product (1 kHz) and sidebands as well:
The digital filter #2 lets some ultrasonic images of the twin tones bleed, but the in-band performance remains at least the same as with the digital filter #1 shown above:
The old 16 bits Burr Brown PCM78 ADCs of the Audio Precision System One probably limits the usefulness of an FFT of the multitone signal from NTTY's test CD. Moreover, the maximum FFT length that the System One is capable of restricts the bin frequency resolution in the bass. Anyway, here is the FFT spectrum of such signal, but from 100 Hz only:
d. Linearity Tests
I am happy to report that NTTY's pressed test CD from a glass master seems to ease linearity measurements with the Audio Precision System One. I wonder if the CD-R I used to use increases noise in the servo of the drive mechanism due to less than optimal reflectivity or other reading issues, which would impact the steadiness of the test signal. Anyway, both channels of the analyzer can now settle on readings down to very low levels:
I used the same scale than Amirm's for its own tests to ease comparison. The level at which the player's output deviates significantly from linearity lies somewhere between -110 dBFS and -120 dBFS. It is possible that the low level hum modulates the level of the test tone at the lowest level.
Here is an FFT analysis of the lowest level -130 dBFS sine signals:
Taking into account the averaging effect, the level of the test tone is shy of roughly 1 dB 'only' from the correct level.
e. Special Tests
Here is a capture of the waveform of a 997 Hz sine at -90.31 dBFS without dither from NTTY Test CD:
The three expected discrete voltage steps are clearly visible.
The Sony DAC is perfectly monotonic, i.e. increasing digital codes produce consistently increasing analogue outputs at the lowest levels. Most probably this characteristic is no longer difficult to get nowadays, but still:
Non-monotonic DAC can also be revealed by another special test which was proposed by Audio Precision in 1991 to check the absence of modulation of the noise floor of D/A converters at different levels (Richard C. Cabot, Noise Modulation in Digital Audio Equipment, AES preprint 3021). This test consists of accumulating on the same graph a third octave analysis of the quantization noise after the removal of a low frequency test signal at different levels from -50 to -100 dBFS. Any change on the shape of the noise floor would signal a modulation of this noise in function of level. Audio Precision quoted experiments previously conducted at Dolby Laboratories that had shown that noise modulation of as little as 2 dB may be audible. Nowadays, this test may have no longer relevance with modern D/A converters, especially sigma-delta converters, but maybe it can still be useful to check ladder type converters. Here is a modern take on this test by accumulating FFT spectra of the different test signal levels:
There is no visible modulation of the noise floor.
Finally, I used special dithered signals made by NTTY on the model of the Pierre Vérany Digital Test CD, which contains unique (non-dithered) tracks to perform a peculiar test called "intermodulation by crosstalk". The theory of operation of this test is as follows: the channel under test plays a 5 kHz tone and the other channel simultaneously plays a 1 kHz tone, both at 0 dBFS. If there is a significant crosstalk between channels, the 1 kHz tone can theoretically intermodulate with the 5 kHz tone to produce on the channel under test a difference frequency of 4 kHz and/or side-bands at 4 and 6 kHz due to amplitude modulation of the 5 kHz tone by the 1 kHz crosstalk tone. This test was designed at a time when most CD players have only a single digital to analogue converter for two channels for cost-savings reason. These CD players had to demultiplexe the left channel from the right by routing the output of the single DAC alternatively to each one of the two channels at twice the CD sampling frequency.
There is only very low level of intermodulation by crosstalk in the right channel. After compensating the effect of the notch filter, the IMD products lie at less than -120 dB under the test tone.
f. Disc Readability
To end the first part of this review dedicated to CD replay, I have used the famous Pierre Vérany Digital Test CD2 to check the ability of the Sony DVP-S9000ES to play damaged discs or disc pressings that are not compliant to the Red Book (RB) specifications. The criteria of failure on a test is either glitches, warping of the output waveform or an increase of THD+N from the nominal value. As NTTY obviously uses the same disc to perform its own tests, I will borrow his table:
| Test Type | Variable parameter(s) | Results |
|---|---|---|
| Variation of linear cutting velocity | 1.4 then 1.2 to 1.4 m/s in 0.05 m/s steps | All tests passed |
| Combined variations of track pitch and velocity | From 1.2 m/s to 1.40 m/s combined with 1.5 µm & 1.7 µm pitch | All tests passed |
| Variation of track pitch | 1.5 µm to 1.7 µm in 0.05 µm steps | All tests passed |
| HF detection level | Variation of the pits/lands ratio from +2 to +18% | All tests passed |
| Drop-outs tests | 0.05 to 0.2 mm (RB spec.) and 0.3 to 4 mm (non-spec.) | All RB spec. tests passed - Pass to 1.25 mm Fails from 1.5 mm |
| Combined drop-out size variation & minimum track pitch | 1.5 µm + 1 to 2.4 mm | Pass to 1 mm Fails from 1.5 mm |
| Successive drop-outs | 2x0.1 mm to 2x3 mm | Pass to 2x1 mm Fails from 2x1.5 mm |
(To be continued in message #2)
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