Hello Everyone,
Let me add my two cents, as I do usually, in a lighter version.
Philips CD 723 - Measurements (Analog out - From CD)
I described my measurements in the post “
More than we hear”, and as I reported them for the
Onkyo C-733 review. Over time, this will help comparing the devices I reviewed.
The Philips CD 723 outputs a high 2.44Vrms. The two channels were matched at 0.03dB (very good).
Let's start with the standard 999.91Hz sine @0dBFS (without dither) from my test CD (RCA out):
Left channel is a little noisier than right, and right channel has more distortion. We are basically missing 1bit of resolution, so 6dB are lost here.
Same but at -6dBFS:
You can also apperciate no power supply related spuria, which is not so often. But that's also explained by the relatively high random noise floor.
Bandwidth is within -0.3dB (not shown), nothing of concern.
The multitone test confirms that we get only 15bits of true resolution:
The JTest is decent:
We see very low side bands but some low level noise as well.
I like to share the THD vs Frequency @-12dBFS, as it's proven to be a key differentiator in many cases:
This is an overlay of left and right channels together with on channel of the Denon DCD-900NE. The Philips has roughly 10dB more distorsion and it's noise dominated in low frequencies. We are far from best in class, but it's still a challenge to hear into music.
Started with the
Teac VRDS-20 review, and on your request + support to get it done (more
here), I'm adding now an "intersample-overs" test which intends to identify the behavior of the digital filtering and DAC when it come to process near clipping signals. Because of the oversampling, there might be interpolated data that go above 0dBFS and would saturate (clip) the DAC and therefore the output. And this effect shows through distorsion (THD+N measurement up to 96kHz):
Intersample-overs tests
Bandwidth of the THD+N measurements is 20Hz - 96kHz | 5512.5 Hz sine,
Peak = +0.69dBFS | 7350 Hz sine,
Peak = +1.25dBFS | 11025 Hz sine,
Peak = +3.0dBFS |
| Teac VRDS-20 | -30.7dB | -26.6dB | -17.6dB |
| Yamaha CD-1 (Non-Oversampling CD Player) | -79.6dB | -35.3dB | -78.1dB |
| Onkyo C-733 | -79.8dB | -29.4dB | -21.2dB |
| Denon DCD-900NE | -34.2dB | -27.1dB | -19.1dB |
| Philips CD 723 (Output Volume at max) | -48.3dB | -31.0dB | -20.7dB |
| Philips CD 723 (Output Volume -1.5dB) | -54.6dB | -67.9dB | -23.2dB |
| Philips CD 723 (Output Volume -3dB) | -54.6dB | -67.9dB | -41.1dB |
I kept some references and will keep the same for other reviews, so you can quickly compare. The Philips CD 723 has digital volume obviously done via an ASRC prior to the conversion. That's the reason why I've put 3 references, at max Volume, and then at -1.5dB and -3dB.
Initially the Philips has no headroom to process intersample overs. But when the volume is digitally reduced in the ASRC (the interpolator), then the headroom increases accordingly, which is logical. So on that perspective, if you're worried about that type of distorsion, you can solve the issue by slightly reducing the output volume.
Stereophile was often using the 3DC measurement as a prof of low noise DAC. It is from an
undithered 997Hz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest symmetrical sign magnitude 16bits PCM signal:
There is a lot of noise in this view and symmetry is not ensured. This is not good result, demonstrating again that we roughly miss 1 bit of resolution in this player.
Other measurements (not shown):
- IMD AES-17 DFD "Analog" (18kHz & 20kHz 1:1) : -72.4dB
- IMD AES-17 DFD "Digital" (17'987Hz & 19'997Hz 1:1) : -71.1dB
- IMD AES-17 MD (41Hz & 7993Hz 4:1): -75.3dB
- IMD CCIF (19kHz & 20kHz 1:1) : -74.3dB
- IMD TDFD (13'58Hz & 19841Hz 1:1) : -86.5dB
- IMD TDFD Bass (41Hz & 89Hz 1:1) : -80.8dB
- IMD SMPTE (60Hz & 7kHz 1:4) : -70.6dB
- Dynamic Range : 95.3dB (from 1khz @-60dBFS)
- Crosstalk: -94dB (100Hz), -92dB (1kHz), -89dB (10kHz)
- Linearity : -80dB
- Pitch Error : 19'999.13Hz (19'997Hz requested) ie -0.0106% (106ppm)
The above are on the low end of what I usually measure. The pitch error is also higher than usual as the clock does not do better than 106ppm precision. I also see that it varies with the temperature.
The player looses linearity, even from dithered signal, as early as -80dB (0.52dB deviation), while many others have no issue going beyond -100dB.
Philips CD 723 - Testing the drive
What would be good measurements if the drive would not properly read a slightly scratched CD, or one that was created at the limits of the norm? The below tests reply to these questions.
| Test type | Technical test | Results |
| Variation of linear cutting velocity | From 1.20m/s to 1.40m/s | Pass |
| Variation of track pitch | From 1.5µm to 1.7µm | Pass |
| Combined variations of track pitch and velocity | From 1.20m/s & 1.5µm to 1.40m/s & 1.7µm | Pass |
| HF detection (asymmetry pitch/flat ratio) | Variation from 2% to 18% | Pass |
| Dropouts resistance | From 0.05mm (0.038ms) to 4mm (3.080ms) | Up to 2mm. |
| Combined dropouts and smallest pitch | From 1.5µm & 1mm to 1.5µm & 2.4mm | Up to 2mm. |
| Successive dropouts | From 2x0.1mm to 2x3mm | Up to 1.5mm. |
The drive of the Philips CD 723 was able to consistently continue playing, without generating typical digital clicks, with dropouts of up to 2mm. The interpolation effect was easy to hear when it kicked-off (at 1.5mm dropouts) and the Philips did not fail to maintain a constant flow with up to 2.4mm dropouts (with lots of clicks). The CD 723 had no issue with variable linear velocity and/or track pitch, as well as with HF detection. These are decent results.
Philips CD 723 - Measurements (Digital out)
The pitch error, which is due to lack of clock precision, prevented me from performing high precision analysis of the digital output. Indeed, when looking at the digital signal, I can see frequency variations since there's no PLL in that case.
For that reason, I don't have high resolution FFT to show, because I get too many windowing error. But by reducing the FFT Length, I can get my computer to be fast enough to capture a usable view (999.91Hz @0dBFS):
You will notice that the software does not see the signal at 0dBFS (but at -0.56dBFS) which means the digital signal is modified before reaching the output. This is not what is on the test CD. In other words, it's not bit perfect. That said, we don't suffer from additional distortion components, as I could see them with the Fiio DM13 for instance.
This is probably again the effect of an internal ASRC as I see the digital output can be attenuated by the remote control.
Conclusion
Volume control done via an ASRC might be practical but it comes with reduction of resolution and impacts the digital output too, in this Philips CD player.
This was low cost CD player at the time, and the max resolution of this player does not go beyond 15bits in the best case scenario.
