Introduction

Lots of words have been spent by now in the hi-fi world about the fatal effects of jitter on the sound of our beloved CD players. I'll try to resume the matter in VERY plain and concise words, the more expert among you are begged to forgive me. Any CD Player picks up the data from the disc according to its internal clock.

This clock is a square wave signal that generally assumes a 0 - 5 V (low - high) value at a given frequency. In order to have our music signal recovered as truly as possible, the clock must show an absolute precision both in terms of frequency and time period. Put in this way, things may look a bit strange but with a picture everything will become evident:

The two clocks shown in the picture have the same frequency but B shows evident jitter. This time distortion causes, during the D/A conversion process, the distortion of the music signal too. Hence, the need for a high precision clock. In most of the integrated circuits dedicated to the extraction of that information, the oscillator that produces the clock is built onboard. Externally, it just needs a quartz crystal for the working frequency.

An oscillator implemented in such a way is hardly the best in terms of precision, since its transistors work along thousand others which the integrated circuit consists of. And, this brings noise into the oscillator itself; to get rid of this problem, a very precise, dedicated-supply oscillator is needed.

And here Mr. Guido Tent comes to help us.

He proposes us a high-precision oscillator with a jitter smaller than 3ps (three sigma). It is available for different frequencies in order to match different CD players, and in different configurations to meet the needs of the individual audiophile accordingly to her/his technical and practical background. The base version, XO, consists of the lone oscillator plus two ferrite rings to be clamped onto the power supply cord. In this case, the customer has to make up a low-noise power supply unit of his own.

X0 Base

The second step, the X02, is an X0 mounted on a small board including a low-noise supply set. The third step, the X03, consists of an X02 improved with a re-clocking SPDIF circuit, and is especially intended for those who use external DACs.

To install an XO, either 0, 2 or 3, the same steps hereunder must be followed: find out what integrated circuit your CD player uses, because the frequency of the oscillator will be chosen accordingly. My VRDS 10, for instance, employs a CDX2500 that requires a 16.3944 MHz clock.

X0 2500

Find the clock signal input pin on the chip. Take the existing quartz crystal away with its surrounding circuits (usually two caps). Connect the output of the new oscillator to the previously identified clock input pin. I remember you that the difference between the X0 and the other two (X2 and X3) lays in the fact that in order to install the XO you need to provide your own low-noise power supply too. Now you can switch your CD player on and, if you've been good at it, everything will immediately work. "Right, but are you telling us what it is like or not?" Ok, ok, here I am. Well, what immediately strikes, and gets even more confirmed later, is the wider array of "spatial" information.

Everything is firmer in its place and easier to track down and to identify. The soundstage does not change in dimension: depth, height and width stay practically the same, but become more precise. Details grow in a substantial amount, even the smallest details are brought to the attention of the listener. I don't quite know how to explain that, it's a feeling of great "cleanliness". But please pay attention, in an already very detailed setup this precision might become excessive, damaging the musical message, making it become almost artificial. Dynamics stay inside the boundaries of reality, substantially unchanged, but thanks to the transients that get faster and sharper, the sound seems prompter and mightier.

Under a tone balance point of view, it's the high frequency range that takes the largest advantage from the work of the new oscillator. It becomes more liquid, rich and harmonic, and I dare say it stretches a bit, though I couldn't tell whether this is reality or illusion. Moving to the lower frequency range things don't run that good, at least in my setup, in particular the bass range looses its softness too much, getting almost dry. In a word, the general sensation - as I was saying - is that of a cleaner, sharper, more ethereal sound, but maybe just a bit less musical and vital. But I wish to point out that this is what happens with my setup, which is already very detailed and analytic on his own.

Therefore, with the XO, it tends to become too much analytic. This problem is therefore likely not to come out with a less unforgiving chain. I wish to remind you that I use my VRDS10 as a transport only, in an integrated CD player the effect of the oscillator should be more evident. re più marcato.

Conclusions

This precision oscillator by Mr. Guido Tent gets the job done, i.e. its effects are evident. In my test some of them have been certainly positive, with better cleanliness and detail, others less, with a slightly cold, less vivid sound. Some patience is needed being the replacement not so immediate, but Guido turned out to be a very patient person answering every question I sent him and allowing me to get the upgrade safely done. What CD players are worthy a try? I tried the upgrade on my VRDS10; cheaper gear should get higher benefits. After all the cost of the item, especially the XO version, is really low; so, if you're a tweaking freak, try it with no hesitation, you could be positively surprised; if you are not, reverse tweaking shouldn't be a problem.