This is a review and detailed measurements of the Onkyo C-733 CD stereo player and transport.
Onkyo C-733 - Presentation
This CD player is from 2005 and was part of the top line of mini components from Onkyo. It was available as a member of the PHA-933 combo including an integrated amplifier, a tuner and this CD player.
The C-733 features a 24bits/192kHz converter from Cirrus Logic (CS4396-KS). Back panel shows two optical digital outputs (to compare DACs
) and RCA connectors. That's all, no phones out as it was available with the integrated amplifier. Same goes with the remote control.
On the back, we get dual SPDIF optical outputs, not very common , and maybe two compare two external DACs
The published specs were the below:
Inside, all electronic cards are labelled Onkyo and well arranged, as far as I can tell.
The elements of interest are:
On the above picture, you can see the CS DAC bottom right. Output stage uses the infamous NE5532. Note some sort of tape positioned on multiple caps, I did not see that elsewhere before.
Using this player was surprisingly pleasant. The drive is extremely fast as it equals the best I have, that is good news. I'm not asking much more than that, and with modern CD players, I don't get it often...
I got this player for 120$ or so, and that was including the amplifier and tuner from the same combo (named PHA-933).
Onkyo C-733 - Measurements (Analog out)
All measurements performed with an E1DA Cosmos ADCiso (grade 0), and the Cosmos Scaler (100kohms from unbalanced input) for analog outputs, and a Motu UltraLite Mk5 for digital.
From now on, I will be consistent with my measurements as I described them in the post “More than we hear”, and as I reported them in the below review. Over time, this will help comparing the devices I reviewed.
The Onkyo C-733 outputs 1.92Vrsm, and there was a slight channel imbalance of around 0.05dB (which is very good). The single-ended outputs are respect the absolute polarity.
Here you go with the 999.91Hz sine @0dBFS (without dither):
Right and left channels are shown and are identical, it's not so often. THD sits at -100dB and so will clear CD Audio content.
I add a view of a 999.91Hz @-6dBFS (without dither):
We see that the distorsion increased by 6dB relative to the carrier. In fact, the distortion remains the same until -9dBFS, at which point it goes a down, to become nearly buried into the quantization noise of the CD Audio, as shown below with a 999.91Hz @-12dBFS (still without dither):
----
With those I see as silent CD Players, I like to show the advantage we can potentially got from Noise Shaping, as this is often used in modern masters. The below is comparison between two test tones of 999.91Hz @0dBFS without dither and with Shape Dither:
We see that the noise floor is lowered by a bit more than 6dB up to 5kHz, which means this player is silent enough to offer 17bits of true resolution.
----
You probably already noticed that this is a very quiet CD player, with minimum power supply–related spuriae in its output (below -120dB at 50Hz) :
----
Bandwidth (now measured from a long term average of periodic white noise) is nearly flat:
We see 0.1dB variation max from 20Hz to 20kHz. We also find the 0.05dB channel imbalance which is a very good result.
----
This is below a view of oversampling filter behavior (from white noise) and together with dual tones 18kHz+20kHz (IMD AES17) :
As you can see, the out of band attenuation is -80dB, which is decent. Artifacts of the conversion (aliases) are therefore well reduced. No sign of massive Noise Shaping either, at least up to 80kHz. From the above, you can also see that the IMD is quite low (-94.6dB).
----
Multitone (1/10 decade) shows a happy CD player, not having issue to clear much more than 16bits of data:
----
This is the Jitter test:
This is an overlay of Analog (bleu) and Digital outputs (red). The Onkyo C-733 does not suffer from Jitter. We see only low level distorsion (additional rays) and two very low level rays on both sides of the fundamental, all of it being of no concerns.
----
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):
I kept some references and will keep the same for other reviews, so you can quickly compare. The results of the Onkyo C-733 mean the oversampling filter has roughly 1dB headroom, which is good because it will prevent intersample-overs and therefore clipping where it's most likely to happen. The Yamaha CD-1 shines here because it's old enough not to have an oversampling filter.
----
Let's continue with the good old 3DC measurement that Stereophile was often using as a proof 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 digital signal in 16bits:
This is a very good trace, proof this player is very silent. We can see our 3 DC levels well defined.
The ringing is due to Gibbs Phenomenon, but also the reconstruction filter:
----
Other measurements (not shown):
The clock is very precise with a variation of only 3ppm.
----
As I did with the Sony CDP-597, I add a "max DAC resolution" measurement test. It is performed from a 999.91Hz sine @-12dBFS with shape dither (from Audacity). I restrict the THD+N span to 20Hz - 6kHz in REW not to account for the noise of the shape dither beyond 6kHz. I take the calculated ENOB and simply add 2bits to it (due to the -12dB attenuation, as 1bits=6dB). The potential maximum, when calculated from the digital WAV file, is 18.7bits under this test. A "transparent" DAC should achieve 18.7bits, ie 100% in this test.
Here are the results compared to others:
The Onkyo is shy of 0.7bits in this test and that is due to the distortion it generates. This is still a very good score.
----
Last but not least, I like to have a look a the THD vs Frequency when using a -12dBFS signal. This has proven to me to be a key differentiator, especially when I'm reviewing an old CD Player using R2R conversion. Here are the results with the Onkyo (Left and Right analog Channels shown) :
I don't need to overlay these results with other players, because it's a refence trace. This view restricts the measurement to THD over 5 harmonics only. Not many CD player achieve the same... And this is one more proof that this player is extremely silent with levels below -9dBFS, its distorsion being buried below the digital quantization noise of the CDA.
Onkyo C-733 - Measurements (Optical Out)
I've seen several of you reviewing CD players using their digital outputs, in case the results could be improved from an external DAC.
The digital output (optical only) is as what we expect it to be, perfect (999.91Hz @0dBFS without dither):
This is what is on the test CD, it’s equivalent to ripping it on a computer, except that here, it is a true live FFT from the S/PDIF TOSLINK output of the Onkyo. Note the very precise 999.91Hz that I get, which means the clock is better than 10ppm in the Onkyo (3ppm in fact, as per the pitch error test I reported before).
The 3DC levels are well represented too, showing no modification of very low level signal:
EDIT : From now on, I will use the intersample overs test at 5512.50Hz @0dBFS, with a phase shift of 67.5°, like I did for the TASCAM CD-200 review. This signal generates an "over" of +0.69dB and so if the signal would be modified before being sent, it would show either a reduction of amplitude or we'd see some sort of saturation. So here we go, the below is a comparison between the WAV File directly processed by the PC, and when played by the Onkyo via the SPDIF Opti out:
The two traces are the same, including the "over" of +0.69dBFS because of the phase shift, meaning there's no modification of the digital output.
Onkyo said in the brochure that they paid attention to the digital outputs, and yes they did. This little player will therefore be a perfect transport.
Onkyo C-733 - 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.
The drive was able to consistently continue playing, without generating typical digital clicks, with dropouts of up to 2mm. The interpolation effect remained hidden to my ears when it kicked-off (at 1.5mm dropouts) and succeeded to maintain a constant flow up to 2mm dropouts. The Onkyo had no issue with variable linear velocity and/or track pitch, as well as with HF detection.
Conclusion
The Analog output of this player is close enough to what's digitally recorded on the test CD and only limited by distortion with the highest test tones. If we can probably find a better external DAC, there's obviously little more to expect.
The drive is fast and absolutely silent, and the digital output is "perfect", meaning the Onkyo C-733 will be an ideal transport.
Well done to Onkyo, and for those of you who still enjoy spinning a CDA, you have more than a competent player here, which you can also use as a transport, of course.
I hope you enjoyed the review!
Onkyo C-733 - Presentation
This CD player is from 2005 and was part of the top line of mini components from Onkyo. It was available as a member of the PHA-933 combo including an integrated amplifier, a tuner and this CD player.
The C-733 features a 24bits/192kHz converter from Cirrus Logic (CS4396-KS). Back panel shows two optical digital outputs (to compare DACs
) and RCA connectors. That's all, no phones out as it was available with the integrated amplifier. Same goes with the remote control.On the back, we get dual SPDIF optical outputs, not very common , and maybe two compare two external DACs
The published specs were the below:
Inside, all electronic cards are labelled Onkyo and well arranged, as far as I can tell.
The elements of interest are:
- VLSC (Vector Linear Shaping Circuitry): This seems to be proprietary and refined analog filtering post DAC, see more from the post of @Scytales.
- Exclusive Direct Digital Path: Onkyo says they took great care of the digital output, which is nice when thinking about using it as a transport. That's also probably why there are two Optical outputs.
- DAC Wolfson 24bits/192kHz: Someone forgot to warn the marketing that they went for a Cirrus Logic (CS4396-KS) instead
- Sony KSS-213CL: as opposed to the KSS-213C which was used in many CD players, the CL version found its way into higher end players, including four Accuphase. I could not find reliable information about the differences between KSS-213C and KSS-213CL.
On the above picture, you can see the CS DAC bottom right. Output stage uses the infamous NE5532. Note some sort of tape positioned on multiple caps, I did not see that elsewhere before.
Using this player was surprisingly pleasant. The drive is extremely fast as it equals the best I have, that is good news. I'm not asking much more than that, and with modern CD players, I don't get it often...
I got this player for 120$ or so, and that was including the amplifier and tuner from the same combo (named PHA-933).
Onkyo C-733 - Measurements (Analog out)
All measurements performed with an E1DA Cosmos ADCiso (grade 0), and the Cosmos Scaler (100kohms from unbalanced input) for analog outputs, and a Motu UltraLite Mk5 for digital.
From now on, I will be consistent with my measurements as I described them in the post “More than we hear”, and as I reported them in the below review. Over time, this will help comparing the devices I reviewed.
The Onkyo C-733 outputs 1.92Vrsm, and there was a slight channel imbalance of around 0.05dB (which is very good). The single-ended outputs are respect the absolute polarity.
Here you go with the 999.91Hz sine @0dBFS (without dither):
Right and left channels are shown and are identical, it's not so often. THD sits at -100dB and so will clear CD Audio content.
I add a view of a 999.91Hz @-6dBFS (without dither):
We see that the distorsion increased by 6dB relative to the carrier. In fact, the distortion remains the same until -9dBFS, at which point it goes a down, to become nearly buried into the quantization noise of the CD Audio, as shown below with a 999.91Hz @-12dBFS (still without dither):
----
With those I see as silent CD Players, I like to show the advantage we can potentially got from Noise Shaping, as this is often used in modern masters. The below is comparison between two test tones of 999.91Hz @0dBFS without dither and with Shape Dither:
We see that the noise floor is lowered by a bit more than 6dB up to 5kHz, which means this player is silent enough to offer 17bits of true resolution.
----
You probably already noticed that this is a very quiet CD player, with minimum power supply–related spuriae in its output (below -120dB at 50Hz) :
----
Bandwidth (now measured from a long term average of periodic white noise) is nearly flat:
We see 0.1dB variation max from 20Hz to 20kHz. We also find the 0.05dB channel imbalance which is a very good result.
----
This is below a view of oversampling filter behavior (from white noise) and together with dual tones 18kHz+20kHz (IMD AES17) :
As you can see, the out of band attenuation is -80dB, which is decent. Artifacts of the conversion (aliases) are therefore well reduced. No sign of massive Noise Shaping either, at least up to 80kHz. From the above, you can also see that the IMD is quite low (-94.6dB).
----
Multitone (1/10 decade) shows a happy CD player, not having issue to clear much more than 16bits of data:
----
This is the Jitter test:
This is an overlay of Analog (bleu) and Digital outputs (red). The Onkyo C-733 does not suffer from Jitter. We see only low level distorsion (additional rays) and two very low level rays on both sides of the fundamental, all of it being of no concerns.
----
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 | -84.6dB | -84.9dB | -78.1dB |
| Denon DCD-900NE | -34.2dB | -27.1dB | -19.1dB |
| Denon DCD-SA1 | -33.6dB | -27.6dB | -18.3dB |
| Onkyo C-733 | -88.3dB | -40.4dB | -21.2dB |
| Denon DCD-3560 | -30.2dB | -24.7dB | -17.4dB |
| Marantz CD-73 | -50.3dB | -52.0dB | -27.7dB |
I kept some references and will keep the same for other reviews, so you can quickly compare. The results of the Onkyo C-733 mean the oversampling filter has roughly 1dB headroom, which is good because it will prevent intersample-overs and therefore clipping where it's most likely to happen. The Yamaha CD-1 shines here because it's old enough not to have an oversampling filter.
----
Let's continue with the good old 3DC measurement that Stereophile was often using as a proof 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 digital signal in 16bits:
This is a very good trace, proof this player is very silent. We can see our 3 DC levels well defined.
The ringing is due to Gibbs Phenomenon, but also the reconstruction filter:
----
Other measurements (not shown):
- IMD AES-17 DFD "Analog" (18kHz & 20kHz 1:1) : -94.6dB
- IMD AES-17 DFD "Digital" (17'987Hz & 19'997Hz 1:1) : -89.8dB
- IMD AES-17 MD (41Hz & 7993Hz 4:1): -93.9dB
- IMD CCIF (18kHz & 20kHz 1:1) : -89.7dB
- IMD TDFD (13'58Hz & 19841Hz 1:1) : -104.4dB
- IMD TDFD Bass (41Hz & 89Hz 1:1) : -102.4dB
- IMD SMPTE (60Hz & 7kHz 1:4) : -84dB
- Dynamic Range : 98.5dB (@-60dBFS, no dither)
- Crosstalk: -136dB (100Hz), -119dB (1kHz), -99dB (10kHz)
- Pitch Error : 19'997.06Hz (19'997Hz requested) ie +0.0003% (3ppm)
- Gapless playback : Yes
The clock is very precise with a variation of only 3ppm.
----
As I did with the Sony CDP-597, I add a "max DAC resolution" measurement test. It is performed from a 999.91Hz sine @-12dBFS with shape dither (from Audacity). I restrict the THD+N span to 20Hz - 6kHz in REW not to account for the noise of the shape dither beyond 6kHz. I take the calculated ENOB and simply add 2bits to it (due to the -12dB attenuation, as 1bits=6dB). The potential maximum, when calculated from the digital WAV file, is 18.7bits under this test. A "transparent" DAC should achieve 18.7bits, ie 100% in this test.
Here are the results compared to others:
| CD Player model or DAC | Calculated ENOB (999.91Hz sine @-12dBFS with shape dither, THD+N span = 20Hz - 6kHz) | Percentage of max resolution achieved (higher is better) |
| OPPO BDP-95 | 18.7bits | 100% |
| SMSL PL-200 | 18.7bits | 100% |
| SMSL PS-200 (from CD player) | 18.6bits | 99.47% |
| Denon DCD-SA1 | 18.5bits | 98.93% |
| Denon DCD-900NE | 18.5bits | 98.93% |
| Onkyo C-733 | 18bits | 96.26% |
| SMSL PL150 | 18bits | 96.26% |
| SMSL PL100 | 17.9bits | 95.72% |
| Sony CDP-597 | 17.5bits | 93.58% |
| Onkyo DX-7355 | 17.3bits | 92.51% |
| Denon DCD-3560 | 17.2bits | 91.98% |
| Yamaha CD-S303 | 16.8bits | 89.84% |
| Accuphase DP-70 | 16.6bits | 88.77% |
| Sony CDP-337ESD | 16.6bits | 88.77% |
| Teac VRDS-25x | 16.5bits | 88.24% |
| Marantz CD-73 | 14.9bits | 79.68% |
The Onkyo is shy of 0.7bits in this test and that is due to the distortion it generates. This is still a very good score.
----
Last but not least, I like to have a look a the THD vs Frequency when using a -12dBFS signal. This has proven to me to be a key differentiator, especially when I'm reviewing an old CD Player using R2R conversion. Here are the results with the Onkyo (Left and Right analog Channels shown) :
I don't need to overlay these results with other players, because it's a refence trace. This view restricts the measurement to THD over 5 harmonics only. Not many CD player achieve the same... And this is one more proof that this player is extremely silent with levels below -9dBFS, its distorsion being buried below the digital quantization noise of the CDA.
Onkyo C-733 - Measurements (Optical Out)
I've seen several of you reviewing CD players using their digital outputs, in case the results could be improved from an external DAC.
The digital output (optical only) is as what we expect it to be, perfect (999.91Hz @0dBFS without dither):
This is what is on the test CD, it’s equivalent to ripping it on a computer, except that here, it is a true live FFT from the S/PDIF TOSLINK output of the Onkyo. Note the very precise 999.91Hz that I get, which means the clock is better than 10ppm in the Onkyo (3ppm in fact, as per the pitch error test I reported before).
The 3DC levels are well represented too, showing no modification of very low level signal:
EDIT : From now on, I will use the intersample overs test at 5512.50Hz @0dBFS, with a phase shift of 67.5°, like I did for the TASCAM CD-200 review. This signal generates an "over" of +0.69dB and so if the signal would be modified before being sent, it would show either a reduction of amplitude or we'd see some sort of saturation. So here we go, the below is a comparison between the WAV File directly processed by the PC, and when played by the Onkyo via the SPDIF Opti out:
The two traces are the same, including the "over" of +0.69dBFS because of the phase shift, meaning there's no modification of the digital output.
Onkyo said in the brochure that they paid attention to the digital outputs, and yes they did. This little player will therefore be a perfect transport.
Onkyo C-733 - 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 was able to consistently continue playing, without generating typical digital clicks, with dropouts of up to 2mm. The interpolation effect remained hidden to my ears when it kicked-off (at 1.5mm dropouts) and succeeded to maintain a constant flow up to 2mm dropouts. The Onkyo had no issue with variable linear velocity and/or track pitch, as well as with HF detection.
Conclusion
The Analog output of this player is close enough to what's digitally recorded on the test CD and only limited by distortion with the highest test tones. If we can probably find a better external DAC, there's obviously little more to expect.
The drive is fast and absolutely silent, and the digital output is "perfect", meaning the Onkyo C-733 will be an ideal transport.
Well done to Onkyo, and for those of you who still enjoy spinning a CDA, you have more than a competent player here, which you can also use as a transport, of course.
I hope you enjoyed the review!
Last edited:
