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At the birth of digital audio, although the specifications were exemplary, the sound quality did not match that of a good vinyl setup. Even today a good vinyl system will give the very best of digital equipment a run for its money.

One of the primary culprits of Digital source components which causes audible loss of sound quality and stereo focus is clock jitter. Within all digital components (CD Players, DACs etc.) is a clock, normally a quartz crystal oscillator. This is used to 'clock' the data through the digital audio circuits and finally to control when the actual D/A converter chips convert the digital data to an analogue voltage or current. This timing is very important and any time domain errors (jitter) are easily heard on playback.

Within all CD players there is a DAC which as the name suggests converts the digital information to an analogue signal. The DAC could be viewed as the source, and the analogue section as the output. In a video system it would be similar to a video player and a TV monitor. The monitor can only show what it is presented with, and cannot make up for any shortcomings in the source. i.e. if you had an old VHS video player producing a noisy output and an excellent monitor, the picture would still be of poor quality no matter how high the resolution of the monitor. If you had an average but good quality TV monitor and a high resolution DVD player, the picture would be of far higher performance than when using an old VHS video and high resolution monitor. The source is all important as it cannot be improved upon as it travels down the signal chain, only degraded. To enable the DAC to work at its best, it has to be fed with a clean, jitter free clock, so that the signal which is fed to the analogue stages is of the highest quality right at the start of the signal chain.

Net-Audio now has a RockClock Master of superlative performance to produce a dramatic uplift on sound quality from your CD Player.

To provide prospective customers with definitive performance data instead of only subjective listening tests, technical measurement of clock performance cannot be argued with. To explain - To buy the best clock available you would need to purchase all the current clocks, fit them to your CD player, listen to them, and then pick the one which sounded ( and should also measure) the best. This is not a realistic way to buy the best performing clock.

Jitter causes a blurring or "vibrating" of the sound, akin to a "picture" of the music being vibrated when you look at it. The more vibration, the more difficult it becomes to see the finer details of the picture, fine lines and edges blur and become indistinct, as does the music with a jittery clock. Clock jitter produces a "vibrating" of the sound from low to high frequencies (20Hz to over 40KHz) then the best way to quantify the performance of a clock would be to measure the clock jitter and plot the "vibrating" of the clock over the audio spectrum from 20Hz to over 40KHz so that the amount of vibration different clocks produce can be compared graphically, the best one being the clock producing the least overall vibration and the least "spot" vibration i.e. a clock may have vibration peak at 10 kHz, producing a bright or aggressive treble sound.

The clock is set to an accuracy of better than 5ppm and normally runs at +/-2ppm when fitted inside the CD player. The absolute accuracy of the clock is relatively unimportant to the operation of the CD player as long as it is not a drastic amount as frequency accuracy does not affect the sound quality at all as some manufacturers would suggest. A figure of +/-20ppm is more than adequate and not at all audible. To put these figures into perspective, a 33 RPM vinyl record played at 45 RPM has an absolute speed error of over 363000 ppm. As the RockClock Master is designed to be around +/-5ppm or better, which is equivalent to a maximum speed error of 165 millionths of an RPM on a turntable running at 33 RPM. The clock frequency on the RockClock Master is settable using a variable capacitor on the circuit board. This can be used to set the exact frequency of the particular crystal. The clock output also has an exact 50:50 mark to space ratio, guaranteed by design.

The specification which affects the sound quality is the jitter measurement and this is where the RockClock Master excels due to careful design and total screening of the clock within a die cast aluminium box.

Introduction of RockClock MK3

Newly introduced in May 2006, the RockClock 3 has had some small but important updates. Small board changes, an improvement to the power supply, updating the decoupling capacitors to Wima polypropylene types and removing the oscillator trimming capacitors have added up to a significant uplift in sound quality. The removal of the trimmer enables the circuit to be 'compressed' slightly, a shortening of signal traces which reduces stray pickup and radiation of electromagnetic fields, produces a more stable, jitter free oscillator. The trimmer has been replaced with a smaller more compact capacitor, which itself is less prone to pickup due to their tiny size. Each lead on the trimmer alone is larger than its replacement capacitor.

The plots below shows the Net-Audio RockClock Master compared to a leading manufacturers CD Clock3. These plots shows the performance (jitter output level over frequency) of the clocks graphically and provides visual indication of the NET-Audio RockClock MK3 performance superiority over the other clocks and also confirms the correlation between subjective listening tests that have been carried out.

Two frequencies are available:- 11.2896 MHz and 16.9344 MHz. A list of CD players and their respective clock frequencies is available Here

For fitting instructions please click Here.


Jitter Plots

The output jitter of the RockClock is extremely low and is virtually immeasurable as can be seen from the spectrum analyzer plots below.

microplt10

Click on the image for larger plot.

This plot shows a well known 3rd generation clock tested under the same conditions.

clock3

Click on the image for larger plot.

This plot shows the test system noise floor.

specnoise10

Click on the image for larger plot.


RockClock Master PCB

Notice the fully screened design which prevents external interference from the electrically noisy environment within a CD player from interfering with the RockClock Masters sensitive clock circuitry.

Dimensions are 62x57x35 mm. The mounting holes are M3 and are spaced 44 mm and 49 mm apart.

The plastic self-adhesive standoffs (9mm high) are available separately. These can be stuck to the inside of the CD player to remove the requirement for drilling holes in the chassis.

This design is protected by copyright.

 


RockClock MK3 CD Player Upgrade

RockClock CD upgrade includes:-

  • One RockClock upgrade PCB
  • Four Self Adhesive Feet
  • Wires required for connection to your CD Player
Total Price excluding P+P = £90.

11.2896 MHz Version

16.9344 MHz Version


RockClock MK3 and Power Supply Bundle

RockClock and PSU Bundle includes:-

  • One RockClock upgrade PCB
  • One Clock PSU upgrade PCB
  • Eight Self Adhesive Feet
  • Wires required for connection to your CD Player
Total Price excluding P+P = £130.

11.2896 MHz Version.

16.9344 MHz Version.


RockClock MK3 and Regulated Power Supply Bundle

RockClock and PSU Bundle includes:-

  • One RockClock upgrade PCB
  • One Regulated Clock PSU upgrade PCB
  • Eight Self Adhesive Feet
  • Wires required for connection to your CD Player
Total Price excluding P+P = £140.

11.2896 MHz Version.

16.9344 MHz Version.