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Old 23rd October 2002, 12:49 PM   #1
ced is offline ced
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Default optimising kwak clock

Installed a kwak clock on my naim cd3.5 over the weekend and, miracle, I didn't short out half the ics! (Though there was a moment of panic when I connected the output up to the wrong pin on the board and the cd drive reached about 3000rpm!)
But I have to say it works very nicely indeed (so thanks alot for the schematic Elso!!!).
I'm etching a new board shortly so I can fit it nicely to the chassis with a much tighter layout but was wondering.... would the addition of a ground plane as a shield on the component side and another board sandwiched to the other side of the tracks, again connected at the star ground, so effectively shielding both sides of the tracks be of any benefit or just act as a large capacitor? I really have little idea about ground planes or shields so any thoughts would be welcome.
Ced
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Old 23rd October 2002, 01:38 PM   #2
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Smile KWAK-CLOCK

Hi Ced,
Glad to hear it is working nicely.
I considered a groundplane on the topside (componentsside of the PCB) but settled for a groundplane at the solderside. All space not occupied by components or tracks is groundcopper.
I made 3-dimensional clocks just by connecting the components in free space. It looks like a modern work of art or a exotic insect but it works. I did not hear any difference between these prototypes and a neat PCB.
Schematic version 6 is just completed. More bass-slamm and punch in the sound. Less glare. Still wondering how a 16.9344MHz clock can influence the sound as perceived
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Old 23rd October 2002, 04:05 PM   #3
ced is offline ced
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Hi Elso,
thanks for that reply. The reason I asked was the datasheet for the AD8561 indicates that a ground plane is recommended for high speed performance (avoids ground bounce and eliminates stray capacitance) but numerous posts on this forum indicate you need to know current loops etc, and basically know what you're doing to design a good ground plane. I've star grounded instead but thought that some shielding might be effective- apparently this is the case with the didden jung regulators for example. I guess I'll just try your ground plane idea instead.
Elso, do you think a low jitter crystal would improve performance also or does it's quality really not matter?
And I know what you mean. Subjectively it seems to me that music is just cleaner and more sharply defined which improves everything slightly. I suppose logical if waveforms are being produced slightly more accurately.
cheers
Ced
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Old 23rd October 2002, 04:53 PM   #4
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Default "Low Jitter Crystal"

Quote:
Originally posted by ced
Elso, do you think a low jitter crystal would improve performance also or does it's quality really not matter?
And I know what you mean. Subjectively it seems to me that music is just cleaner and more sharply defined which improves everything slightly. I suppose logical if waveforms are being produced slightly more accurately.
cheers
Ced
Hi Ced,
The question for a low jiitter crystal I get over and over again.
Just what is a low jitter crystal AT-cut, BT-cut or.......?
I usyually advice to use the crystal from the CDP as you have it to remove anyway and it has the right frequency.
The qualifications I was giving with respect to the sound were for the new version 6. You builded version 5. The new clock is the "breakthrough" design and it is pitty it is not number 7. It is not difficult to modify version 5 to version 6.
Thanks go to Wildmonkeysects and On for stimulating suggestions for this ongoing project

Good luck.
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Old 23rd October 2002, 05:03 PM   #5
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Do you have any jitter specs on your clock?

Stu
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Old 23rd October 2002, 05:15 PM   #6
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Default Jitter Specs

Quote:
Originally posted by maczrool
Do you have any jitter specs on your clock?

Stu
Hi maczrool,
No I don't have any jitter spec. A friend who builded my clock5 is working on that but the results will not be obtained before Christmas. If I may believe Guido Tent the jitter spectrum is also of importance but I don't own that kind of 30k$$$ equipment. And if I had 30k$ I would............. ......... and ...
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Old 24th October 2002, 10:27 AM   #7
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Hi Elso,

could you mail me the current version of your project? Thanks!

ced,

regarding low jitter crystals, it might well be possible that some cuts have certain advantages. I would especially like to see results with those new telecom mesa-etched crystals, but they are not available in multiples of 44.1 kHz.

Anyway, all the crystals we usually see are AT-cut. An argument can be made that the higher order resonances are sharper, so an overtone crystal might be advantageous. On the other hand, it complicates the oscillator circuit. Pick your poison.

One thing is clear though: try to find the lowest series resistance you can. Those small cans which are only 3 mm high have small crystals. Typical R_s values are 2-3x what you get from the medium sized can (HC-49 or something). So even if you don't have access to specs, picking the biggest can you can find is a good idea.

Eric
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Old 24th October 2002, 10:50 AM   #8
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Hi Elso..
Is it possible to mail me a copy of version 6?
Thanks in advance
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Old 24th October 2002, 10:58 AM   #9
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Default crystals

Hi capslock,
Well there is one parameter already that sounds promising, and indeed looking at the crystals from the likes of LCaudio etc, they are all the large can ones not the small ones you mentioned and indeed were in my CD.
There seem to be several other parameters to crystals like 'frequency/temperature stability, calibration tolerance and operating load capacitance'; knowing what ones affect sound and what are irrelevant is the rub.

It does seem logical that the crystal is going to have an effect on ultimate performance like any other component in the circuit.
Having said all that, Elso's circuit really is good! Was listening this morning and after 4 days burn in it is sounding better and better.

ced
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Old 24th October 2002, 01:30 PM   #10
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Would a kwak clock make any sense in a DacMagic II?
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