This is a review and detailed measurements of the Onkyo C-733 CD stereo player and transport.
Before starting, please note that I'm not using an AP but REW software with a Motu Ultralite MK5 pro interface. This setup has its limitations, but to test a pure CD Player, it's good enough.
Over the last two years of experiencing CD Players measurements, I came to make myself a Test CD. And after several reviews here and feedback from many members, I'm happy to share the latest version Test CD which has much improved over the last weeks (thanks again to @restorer-john and @AnalogSteph). I will keep on updating this review with the latest edition of the test CD.
One important note: since the input gain of my measurement interface (Motu) can only be adjusted by steps of 1dB, and because not all CD players output a precise exact 2Vrms output, I had to set a convention for my tests, which is the below:
The reason for this review is mainly after I read the review of the Cayin Mini-CD MKII. Since I'm used to test old CD Players, I wanted to perform measurements of an older Japanese mini CD Player.
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 part 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.
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)
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 invert 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 little down. That means THD ranges between -94dBr to -100dBr from 0dBFS to -30dBFS, and that is very good as it ensures a wide dynamic.
The below is a new measurement with shaped dither added to the signal and compared to no dither:
This is to see if the player would benefit from shaping the noise below 10kHz. Here the decrease, by roughly 5dB, of the noise floor is limited, so not much is to be gained from shaping the noise.
And to make the above clearer, the below is the same view but taken from the digital files:
Notice the change in scale. This is the benefit we can expect from shaping the noise and we are not there with the Onkyo.
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 -0.2dB at 20Hz and -0.1dB at 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 (AES17) :
As you can see, the out of band attenuation is 90dB, which is decent. Artifacts of the conversion (aliases) are therefore well reduced. No sign of massive Noise Shaping either, at least up to 48kHz.
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 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) 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 (need to update them with new test set, be patient) 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.
Stereophile was often using the 3DC measurement as a prof of low noise DAC. It is from an undithered 1kHz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest sign magnitude digital signal:
Not so bad and only disrupted by low level noise that I already mentioned (see further down the same capture from digital output to understand what it should be).
Other measurements (not shown):
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, with one digital channel) :
It is the best measurement I've seen (of this one), equal to the best CD Players I own. The red trace is the digital out. This view restricts the measurement to THD over 5 harmonics only. What we see is that the DAC of this player adds only 2dB of distortion at 1kHz (plot), and more at low level, but of no consequences. I am impressed simply because I've never seen better and often (much) worse.
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.
First the digital output (optical only) is as what we expect it to be, perfect (999.91Hz @-0.01dBFS 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.
Another way to look at the digital output quality, and that I suggested here, is to use an undithered 1kHz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest sign magnitude digital signal, which is what we get with the Onkyo:
The ringing is due to Gibbs Phenomenon.
The below is new from the latest Test CD, and shows an overlay of 999.91Hz @-0.01dBFS without dither and with shaped dither:
This demonstrate again no modification of the digital signal as it is on the Test CD. So, a little more could be expected from a much better external DAC.
Onkyo said in the brochure that they paid attention to the digital outputs, and yes they did.
Conclusions
The Analog output of this player is close enough to what's digitally recorded on the test CD and only limited by low level analog noise. If we can probably find a better external DAC, there's obviously little more to expect.
Well done to Onkyo, and for those of you still enjoying spinning a CDA, you have more than a competent player here, which you can also use as a transport.
I hope you enjoyed the review, and again let me know how to improve and if you have questions. I have recorded all the measurements and if you want me to publish others or run one of your choice, feel free to ask.
Thank you.
————
Flo
Before starting, please note that I'm not using an AP but REW software with a Motu Ultralite MK5 pro interface. This setup has its limitations, but to test a pure CD Player, it's good enough.
Over the last two years of experiencing CD Players measurements, I came to make myself a Test CD. And after several reviews here and feedback from many members, I'm happy to share the latest version Test CD which has much improved over the last weeks (thanks again to @restorer-john and @AnalogSteph). I will keep on updating this review with the latest edition of the test CD.
One important note: since the input gain of my measurement interface (Motu) can only be adjusted by steps of 1dB, and because not all CD players output a precise exact 2Vrms output, I had to set a convention for my tests, which is the below:
- If the 0dBFS output of the CD player matches the input of the Motu no higher than -0.6dBFS, then I don’t adjust the input gain of the Motu.
- From -0.59dBFS up to 0dBFS, I reduce the input gain by 1dB to prevent clipping the Motu ADC.
The reason for this review is mainly after I read the review of the Cayin Mini-CD MKII. Since I'm used to test old CD Players, I wanted to perform measurements of an older Japanese mini CD Player.
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 part 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.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:
- VSLC (Vector Linear Shaping Circuitry): This is proprietary noise shaping which was featured on a number of CD Players from Onkyo.
- 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)
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 invert 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 little down. That means THD ranges between -94dBr to -100dBr from 0dBFS to -30dBFS, and that is very good as it ensures a wide dynamic.
The below is a new measurement with shaped dither added to the signal and compared to no dither:
This is to see if the player would benefit from shaping the noise below 10kHz. Here the decrease, by roughly 5dB, of the noise floor is limited, so not much is to be gained from shaping the noise.
And to make the above clearer, the below is the same view but taken from the digital files:
Notice the change in scale. This is the benefit we can expect from shaping the noise and we are not there with the Onkyo.
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 -0.2dB at 20Hz and -0.1dB at 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 (AES17) :
As you can see, the out of band attenuation is 90dB, which is decent. Artifacts of the conversion (aliases) are therefore well reduced. No sign of massive Noise Shaping either, at least up to 48kHz.
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 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) 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 | NA | NA | -17.6dB |
| Yamaha CD-1 (Non-Oversampling CD Player) | -86.4dB | -84.9dB | -78.3dB |
| Onkyo C-733 | -88.3dB | -40.4dB | -21.2dB |
| Denon DCD-900NE | NA | NA | -19.1dB |
I kept some references (need to update them with new test set, be patient) 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.
Stereophile was often using the 3DC measurement as a prof of low noise DAC. It is from an undithered 1kHz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest sign magnitude digital signal:
Not so bad and only disrupted by low level noise that I already mentioned (see further down the same capture from digital output to understand what it should be).
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 : 96.5dB
- Crosstalk: -130dB (100Hz), -119dB (1kHz), -100dB (10kHz)
- Pitch Error : 19'997.06Hz (19'997Hz requested) ie +0.0003%
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, with one digital channel) :
It is the best measurement I've seen (of this one), equal to the best CD Players I own. The red trace is the digital out. This view restricts the measurement to THD over 5 harmonics only. What we see is that the DAC of this player adds only 2dB of distortion at 1kHz (plot), and more at low level, but of no consequences. I am impressed simply because I've never seen better and often (much) worse.
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.
First the digital output (optical only) is as what we expect it to be, perfect (999.91Hz @-0.01dBFS 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.
Another way to look at the digital output quality, and that I suggested here, is to use an undithered 1kHz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest sign magnitude digital signal, which is what we get with the Onkyo:
The ringing is due to Gibbs Phenomenon.
The below is new from the latest Test CD, and shows an overlay of 999.91Hz @-0.01dBFS without dither and with shaped dither:
This demonstrate again no modification of the digital signal as it is on the Test CD. So, a little more could be expected from a much better external DAC.
Onkyo said in the brochure that they paid attention to the digital outputs, and yes they did.
Conclusions
The Analog output of this player is close enough to what's digitally recorded on the test CD and only limited by low level analog noise. If we can probably find a better external DAC, there's obviously little more to expect.
Well done to Onkyo, and for those of you still enjoying spinning a CDA, you have more than a competent player here, which you can also use as a transport.
I hope you enjoyed the review, and again let me know how to improve and if you have questions. I have recorded all the measurements and if you want me to publish others or run one of your choice, feel free to ask.
Thank you.
————
Flo
Last edited:
