Kwak Clock layout ???

[Lyra]

I am about to make a board (Eagle) for my KC7 implemantation....

What will be the "best" choice of:

-ground plane on component side
-ground plane on back-side
-both.....??


I am also implementing a 74HC125 logic to be able to drive the output when the board is placed close to the DAC, and the clock is feed backwards via 50ohm coax.
Should this logic, and corresponding transistor (2N4401) have it's own +5V supply, or could I just use +5V from the clock ???????


Lyra

[Guido Tent]

Originally posted by Lyra
I am about to make a board (Eagle) for my KC7 implemantation....

What will be the "best" choice of:

-ground plane on component side
-ground plane on back-side
-both.....??


I am also implementing a 74HC125 logic to be able to drive the output when the board is placed close to the DAC, and the clock is feed backwards via 50ohm coax.
Should this logic, and corresponding transistor (2N4401) have it's own +5V supply, or could I just use +5V from the clock ???????


Lyra

Hi

You may look here for layout suggestions

http://members.chello.nl/~m.heijlige...decoupling.pdf

regards

[Elso Kwak]

Hi Lyra,
First remember electrons don't take sharp corners so avoid this situation by making rounded tracks.
http://www.audiotuning.de
(Click on Precision Clock)
To get the ground noise to an absolute minimum use a ground plane. See also:
http://www.national.com/rap/Story/0,1562,18,00.html
To quote from Audiocom:
The basic platform of Superclock II is its printed circuit board. This is formed as an extremely low impedance ground plane over which the components are placed. Very low impedance ground planes contribute to signal quality and are essential when handling radio frequency signals which are of exceptionally low distortion and phase jitter. The ground plane shields the radio circuits from the invisible capacitor formed when the board is mounted close to metalwork
Link:
http://www.1st-4-audio.com/control/n...asp?a=105&z=15
Even better go for a 4-layer board:
http://www.lcaudio.dk/com/intlcl.htm
Carbon composition resistors have the lowest inductance and should be used, preferentially in SMD format.
Also note that even a short trace on the PCB has inductance. So keep traces as short as possible, preferentially below one inch.
As for the power supply I quote from
http://www.trichordresearch.com/cdupgrades.html
Independent Power Supply available to isolate clock frequency noise from the rest of your CD player and also reduce other digital noise from the player entering the clock circuit.
Please see also:
http://www.net-audio.co.uk/clockpsu.html
Most authoritative paper:
http://www.analog.com/Analog_Root/st...nal_Sect10.pdf
(Page 17 and further)
Lyra I hope this answers your questions.

This entire post has been spell checked by Word in Windows.

[Guido Tent]

Originally posted by Elso Kwak
Hi Lyra,
First remember electrons don't take sharp corners so avoid this situation by making rounded tracks.
http://www.audiotuning.de/english/index.html
(Click on Precision Clock)
To get the ground noise to an absolute minimum use a ground plane. See also:
http://www.national.com/rap/Story/0,1562,18,00.html
To quote from Audiocom:
The basic platform of Superclock II is its printed circuit board. This is formed as an extremely low impedance ground plane over which the components are placed. Very low impedance ground planes contribute to signal quality and are essential when handling radio frequency signals which are of exceptionally low distortion and phase jitter. The ground plane shields the radio circuits from the invisible capacitor formed when the board is mounted close to metalwork
Link:
http://www.1st-4-audio.com/control/n...asp?a=105&z=15
Even better go for a 4-layer board:
http://www.lcaudio.dk/com/intlcl.htm
Carbon composition resistors have the lowest inductance and should be used, preferentially in SMD format.
Also note that even a short trace on the PCB has inductance. So keep traces as short as possible, preferentially below one inch.
As for the power supply I quote from
http://www.trichordresearch.com/cdupgrades.html
Independent Power Supply available to isolate clock frequency noise from the rest of your CD player and also reduce other digital noise from the player entering the clock circuit.
Please see also:
http://www.net-audio.co.uk/clockpsu.html
Most authoritative paper:
http://www.analog.com/Analog_Root/st...nal_Sect10.pdf
(Page 17 and further)
Lyra I hope this answers your questions.

This entire post has been spell checked by Word in Windows.

dear all,

At the freqs the round edgess are nonsense (if you know how the currents run and which parameters affect the routing of the current).

The impedance of the groundplane is not well understood by many designers, including the Audiocom guys (see above, and realise that currents run in loops).

A 4 layer board may be needed if the clock signal runs at bigger distances, like in our DAC design. I see no reason in a clock circuit, 2 layers are enough, at least that is what my measurements indicate.

Bottom line:
Control the currents through the groundplane, by making sure they travel through the shortest portion (i.e. place decoupling cap closest to the gnd pin of a chip)

Reduce RF currents by placing series impedances in supply and clock / data lines

Organise the floorplan in a logical way so the higheste frequencies / currents travel shortest way

NEVER interrupt the groundplane

By doing so, we achieved a virtual equipotential groundplane, now connect / decouple all component references (including their ground connections) to ground

succes

[Lyra]

This is my PCB-design as for now.
There might be some faults here and there. Keep in mind that this is my first layout using Eagle.....

BTW: the size of the board is aprox. 50x80 mm.

If there are something that look's not OK, please shout out

Lyra

[peranders]

The layout seems pretty OK to me but two things:

1 those 1 uF, why don't choose small 1 uF/63 V polyester? Maybe you chould go for 10-100 nF + 10 uF?

2 The 74HC IC hasn't got a decoupling cap close to pin Vcc.

Maybe you should consider SMD because this is better in almost all resepcts and it's not particulary hard to solder. Go for 0805 parts and SOT23 transistors.

[Guido Tent]

Originally posted by Lyra
This is my PCB-design as for now.
There might be some faults here and there. Keep in mind that this is my first layout using Eagle.....

BTW: the size of the board is aprox. 50x80 mm.

If there are something that look's not OK, please shout out

Lyra

Hi Lyra

one remarks, as my response is limitted as I do not have the schematic at hand

You place the ferrite bead closer to the chips than the decoupling caps. I'd suggest to swop these, the cap should realy be close to the chips

succes

[peranders]

When it comes to traces, always make them as short as possible, cut the corners also. Avoid 90 deg angles. Still I think you really should test SMD because smallness is very positive when it comes to digital circuits and oscillators. Not everything have to be SMD but resistors, < 100nF caps, transistors (regulators), IC's. The crystal can be holemounted.

Mask the groundplane in the skrew holes so the screw and/or the distance not make contact with the groundplane.

Look at the picture below.

[Lyra]

A (little) revised version......

[Lyra]

....and in more real size....