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It is no secret that a clock source that produce the least possible jitter is the basis of getting excellent sound from your digital gears.  Just study the architectures of new High end transports and DAC from Esoteric---external dedicated clock generators.  Same for Other high-end guys, with External Word Clock Inputs for their DACs and Transports and other various forms of architecture to ensure minimum amount of clock jitter in their systems.

A clock is essential by design for Digital-to-analog conversion of Signals (audio or video) to take place.  A good clock will generate much less conversion errors (due to lower levels of jitter) than a bad clock.

This translate to lower noise and distortion components generated. As a result ...

... for audio you WILL hear :

• Less Grain.  

• More Resolution.  

• More Transparency.

• Smoother and extended Highs.

• Tight, Deep and Fast Bass.  Most importantly, a more musical presentation to the sound.

.... for Video, you WILL see: 

• Sharper Image. 

• Less Noise and Artifacts. 

• Truer Colours.  

• Blacker Blacks.  

• More Contrast. 

•  More detailing in the Video.

This is even more prominent for Video, as Video processing in the digital domain is much much faster than audio, and hence even less tolerant of bad clock performance.

With regards to measurement of video performance, I can relate a situation when I am designing the motherboard for Philips 963sa, while I was still in philips....

The standard analog video measurement equipment used is the VM700T by TEKTRONIX (which cost a whopping USD$50K. )  One of the measurement for Analog Video Quality is S/N ratio, where a full level white signal is input to the player and a FFT (fourier transform) measurement is taken from the video output of the player.  The FFT measurement is such that any other signals that comes out from the player besides the white level input is rendered as noise.  It is then ratioed against the white signal and hence the signal to noise ratio of the system can be obtained.  The noise components usually includes the system noise of the player, video outputstage noise and out-of-band noise generated by the video DAC's (main component) etc.

FYI in audio, as new generation DACs uses high oversampling rates to convert the audio digital data to audio, a low jitter master clock is crucial to achieve excellent performance.  I have tried it and results have shown me that compared to a high jitter clock, a low jitter clock produces much less out-of-band noise (less than half) at high frequencies.  This means that there is less distortion elements produced (as out-of-band noises are by-products of DAC conversion process).  This is the main reason for the improvements in Audio.

Anyway, when we first designed the 963 motherboard, for the Video clock we tried to save cost (what else?)  by using a PLL to derive the clock rather then a crystal oscillator.  A PLL will introduce jitter to a derived clock signal.  As a result?  The S/N of the video output dropped to unacceptable level of around 65dB.

When we then used the clock oscillator which generates much less jitter, the S/N measurements goes back to around 78dB.  Bearing in mind that a 6dB difference means a 50% reduction we can see that much less noise is generated when a low jitter clock is used in video and with audio.  Why is this so?  This is because much less out-of-band noise is generated when a low jitter clock is used as compared to a high jitter clock.  In audio, the effective is very pronounced for high-frequency signal, as the digital data density and conversion rate is much faster, say for a 20Khz signal vs a 20hz signal, and many out-of-band noise is generated at high frequencies.  As video processing is many many times faster than audio  (Mhz vs Khz) the measurement difference is even more pronounced.

Consider that an aftermarket clock (TentLabs/LC Audio/Audiocom etc) has even much less jitter than the standard crystal oscillator I used for the 963sa, I have no doubt that the measurements will be even further improved.  This is also the findings from my customers who have installed a clock for their video players, who finds much "blacker" blacks, sharper images and more vivid colours, which is consistent with effects of  reduction of analog video out-of-band noise due to lower jitter of an aftermarket clock

Sad to say, despite the apparent need for a good clock, 99% of the DVD players, including the highend ones (Denon 2900/Denon 3910/Denon5910/Pioneer 755ai/Pioneer969/ Philips 963sa etc) are only using generic clocks which costs maybe USD$1 max!!!

Installing a clock in your DVD is much more worth it, because it improves both audio (SACD/DVD-A,CD/DVD for multistandard players)  and video playbacks at the same time, as the DVD systems uses 1 clock to run both the audio and video sub-systems.  

It will also improve your digital output, as the reduced jitter levels on the digital output data will improve your AV processors decoding and in turn improves the decoded sound.

However, installing a clock in DVD is very difficult for the layman, as DVD players nowadays are made via surface mounted parts which requires special tools to remove properly without damage of the PCB.  This is also made worse by the complexity of current DVD players with multiple clocks running around (for Example, do you know that there are 3 clocks in 963sa?), making it difficult to isolate the right clock to change.

Here is a list price of popular clock Modules available on the web:

• LC Audio X03 + Dedicated Power Supply : S$555 (Euro $255.39).

• Trichord Research Clock 4 + Dedicated Power Supply :$636 (Pounds $205)

• Audiocom Super Clock3 + Dedicated Power Supply : $1012.92 (Pounds $324.50)

Add to the above shipping costs and installation costs, you can see that clock installation is very high in Singapore !!  And this is the main reason why even though many audiophiles and videophiles know that clock upgrades are very good, they are not able to justify installation of the clock modules into their players.

Well, there may have been non before ... but now there are EAM Clock Products !

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