GRIMM AUDIO CC1 & CC2

... what they say ...

My Hi-End

Leo Yeh

"The CC1 is a poisonous device"

See link to full review above

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HVT Netherlands

Marnix Bosman

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If you have followed audio technology a bit in recent years, you know that there is a lot of attention for jitter. After linearity, the increase in bit resolution and sample frequency, this subject is also receiving more attention in digital audio.

Internationally, there is much discussion and writing about jitter. However, jitter is not a simple matter, and unfortunately, a lot of nonsense is also proclaimed about it. There is much debate about the influence of jitter and the sense of suppressing it. One of the reasons is probably that jitter is not easy to measure. Experts and specialists agree, however, that the influence should not be underestimated and that low jitter figures make a significant contribution to overall sound quality. Creating a low-jitter device, however, is not simple. Worldwide, there are only a few companies that really have a good grasp of this matter. We can therefore be proud that a small Dutch company operates on the front lines. The CC1 master clock generator from Grimm Audio probably belongs to the best of its kind.

The Dutch brand Grimm Audio will not ring a bell for most HVT readers. However, the names behind this brand probably will. The brand is the brainchild of four people, namely namesake Eelco Grimm, Bruno Putzeys, Guido Tent, and Peter van Willenswaard. Besides sound engineer Eelco Grimm, without wanting to do other Dutch designers a disservice, probably the three best audio technicians that the Netherlands currently has have gathered. Bruno Putzeys has a background at Philips where he worked on the now-famous UcD amplifiers, among other things. Nowadays, he is active with those same amplifiers for the Groningen-based Hypex. Guido Tent is the namesake of Tentlabs and also started at Philips. With his company Tentlabs, he has become a specialist in clock modifications for CD players and D/A converters and a supplier of various modules for upgrading and modifying audio equipment. Peter van Willenswaard will not be unknown to many. As a journalist, he has written many legendary articles for Audio & Techniek, HVT, Pro Audio Magazine, and the American Stereophile. Nowadays, he works as an independent technician, designer, and consultant from his company AudioMagic, where he focuses on both digital and analog (mostly tube) techniques. Eelco Grimm, finally, has been the editor-in-chief of Pro Audio Magazine for many years alongside his recording work and has also written several articles for HVT. Nowadays, he is a lecturer at HKU (University of the Arts Utrecht) in the Department of Art, Media, and Technology. In 2003, they founded Grimm Audio with the goal of developing high-quality studio equipment. It is known that the four do not just walk the beaten paths and only settle for the best. The first product was the AD1 A/D converter. Meanwhile, there are more products such as the subject of this story, the CC1 word clock generator.

Copying digital data is relatively simple. As long as no bits are lost or bit errors are made, there is no problem. In an A/D or D/A conversion, the clock becomes important. A completely correct formulation is that the clock is important as soon as a time-based conversion takes place, such as an A/D, D/A, or a sample rate conversion. The clock signal has a direct influence on the behavior of the converter. A perfect master clock is a square wave with very stable timing and straight edges. As soon as variations in timing occur, one speaks of jitter. Another problem is distortion of the clock signal. A combination of jitter and signal distortion can of course also occur and makes a regular conversion moment only less clear. Due to the timing variations, distortion of the signal occurs. The influence of jitter can vary greatly from almost inaudible to quite extreme. Jitter is generally expressed in a unit of time. In many cases, a time in picoseconds (1 ps = one trillionth of a second) is specified.

A word clock signal with and without jitter

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The effects of jitter

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... where the simple rule applies : ‘the lower, the better’. There is much discussion about how low jitter must be to become inaudible. Nowadays, however, it is generally agreed that several tens of picoseconds are already clearly audible and that the influence also strongly depends on the frequency of the jitter. For this reason, Grimm Audio tries to use a slightly different formulation in which this frequency factor is made clear. It is a bit too far to describe this in detail here, but more technical reading material on this can be found on the Grimm Audio website under the heading info.

The master clock in CD players is usually based on a crystal. The quality of this depends on the crystal, the active circuitry, the power supply, and the sine to square wave converter. The clock signal must be distributed, and it can go wrong there as well. A clock signal is a high-frequency signal that must be treated as such. The choice of components, the mechanical and electrical construction all influence the jitter specs. Interference signals, such as from a power supply, can also throw a spanner in the works. Jitter can arise in a device but can also occur during transport between two devices. We then speak of interface jitter. Peter van Willenswaard was one of the first to report on the sound differences of CD drives.

These differences can be attributed to interface jitter. Research has shown that jitter can have a completely random character, similar to noise, or a specific frequency, or a combination of both. In the case of interface jitter, the clock detection is also influenced by the audio data, which can lead to ‘data correlated jitter’. All forms of jitter are, of course, undesirable, but especially jitter with a specific frequency or a correlation with the audio is clearly audible.

The CC1v2

The CC1 is developed for the professional market. This device generates a super stable master clock with unprecedented low jitter levels. Partly responsible for this low number is the in-house developed and fully discreetly built VCXO (Voltage Controlled X-tal Oscillator). This VCXO is prominently hidden on the board under a black cover with damping material to prevent mechanical and acoustic vibrations as much as possible. Vibrations prove to have a significant influence on performance. The clock signal is sent out as a word clock signal via various outputs. To use this word clock signal, a device must be equipped with a word clock input. In consumer equipment, this is not yet very common, although more and more high-end devices with such a provision are appearing.

However, the CC1 can also be used in another way. The device also has a reclock function on board. The built-in PLL offers a great degree of jitter suppression, allowing the CC1 to be used as a reclocker between a digital source and a converter.

On the front of the CC1, you choose a base frequency (44.1 or 48kHz), after which you set the multiplication factor (1x, 2x, 4x) for the word clock outputs. In this way, you can create all sample frequencies up to 192kHz. The CC1 has no less than 16 word clock outputs divided over two groups. Next to each output group are dip switches that allow the output impedance and phase of the word clock outputs to be adjusted. As a rule, the impedance is 75 Ohm, but experience shows that not every manufacturer adheres to this neatly. In this way, you can make a perfect adjustment. In addition to the two base frequencies, the CC1 also has a slave mode. The CC1 then ‘looks’ at its AES/EBU or word clock input and uses the internal PLL to synchronize the CC1 to this clock. The PLL in the CC1 locks very slowly to the input signal. This PLL, also developed in-house, offers a very high degree of jitter suppression over a wide frequency range. Especially the high suppression from very low frequencies (0.1Hz) is a special feature of this PLL. A reclocked copy of the input signal based on the low-jitter clock of the CC1 then appears at the AES/EBU output.

19 rates that can be clocked externally. Only my GML A/D converter (George Massenburg Labs HRT9300) offers this feature. Therefore, for this test, my setup was temporarily expanded with an Esoteric SA-10 SACD player. As digital sources, I also had my Teac VRDS-10, Denon DVD-1930, and Logitech Squeezebox. Other devices present were my Langevin UltraAnalog DAC, Genesis Digital Lens, and usual playback system. The Digital Lens was a nice device in this case. This device receives a digital audio signal, temporarily stores it in RAM, and then reclocks it based on its own low-jitter clock. It then displays the clock deviations (in ppm) of the incoming digital signal compared to its own clock. The Digital Lens is not an absolute measuring device but is an interesting comparison for the reclock function of the CC1.

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Listening

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A device like the SA-10 is at a very high level in terms of playback. Esoteric has beautifully constructed the device, and fundamentally, this device sounds truly amazing. You would expect that not much improvement is possible. Yet, providing a super stable external word clock still realizes improvements. Even greater improvements than I had expected. The sound actually wins on all possible points. The playback becomes tighter, more detailed, and the sound image is also calmer. There is even more air around the instruments, allowing you to look even deeper. Especially the calmness in the sound image and the ease with which the stereo image is built are remarkable. Grimm advises to drive the DAC with the maximum possible sample frequency. With the SA-10, I did not directly perceive a noticeable advantage. When using the CC1 as a reclocker, I hear similar improvements that I also observed with the SA-10. My Langevin DAC is a classic multi-bit with a solid and defined low. With the CC1 between the transport and the DAC, I get a similar effect as with the Digital Lens. The low becomes tighter and gains definition. It is as if you are getting an octave more. Especially the ease and calmness you get with a low-jitter control is great. I could not easily express a preference for the Lens or the CC1, but my inclination was strongly towards the CC1. With this clock, you always win, although the impact varies from situation to situation. With a mediocre transport like the DVD-1930, it is huge, and with the VRDS or SA-10, it is relatively much less.

However, it is an improvement every time. It is a matter of trying whether it has a significant effect in your situation.

Conclusion

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That jitter has more impact is once again proven by the CC1. I believe that the device will provide an improvement in almost any setup, although the impact will differ from device to device. The CC1 is intended as a word clock generator, but since not everyone has a device with a word clock input, the reclock function of the CC1 gives the device extra appeal. Whether the CC1 brings something for you is difficult to say in advance and is therefore a matter of trying.

Ten to one that your system will improve because the clock in the CC1 is really incredibly tight. I think they are not easily found elsewhere.

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