differential clock

[Bernhard]

Originally Posted by EUVL

I guess you meant AD96687 ....

No, I have the older part AD9687, specs differ only marginally.

Clock with and without shield.
I was lucky to have a transformer cover that fits exactly my oscillator pcb

[Bernhard]

Originally Posted by EUVL

Why use 2SK152 instead of other JFETs ?
And why not an extra (JFET) driver stage at the oscillator for the comparator a la Hagclock ?

I have a bunch of sk152, as well as the AD, and it is a RF FET, perhaps others are better ?

Is it necessary to load the oscillator with a very high impedance , the extra buffer stage could add another noise and distortion ?

If you look at the schematic, I use 1 k shunt on the input of the AD, that gave an improvement while the termination of the ECL parts was't optimal.

Now it does not seem to make a difference at all.
But I will do a listening test.

The other option that I will try later, is putting a balanced crystal filter between oscillator and comparator.
Though it looks very clean to me already.

About shielding the clock, left with shield, right without:
Without shield would be even worse if there would not be the groundplane of the motherboard shielding the solder side of the oscillator already.
This is 100 dB displayed. The sidebands are 50 Hz noise obviously.

[Bernhard]

Originally Posted by bordins

A friend of mine also explained to me that the differential signal can become a noise generator, into other parts of the circuit.

Can we make PCB trace for the clock output ? Should we choose point-to-point floating cabling instead, like in the products from Audiocom (single-ended, btw).

If so, which cable is appropriate ?

Can you enlighten me why that should happen ?

The setup is differential from oscillator to comparator, differential from comparator to ECL/TTL translator, single ended from ECL/TTL translator to reclocker and divider, the translator has two outputs.

I use SMB connectors between boards everywhere except here, the distance between the oscillator and the comparator is short.

Soon I will test ECL reclocking which means again differential from comparator to ECL flipflop and level translators on input and output.

Final implementation could be ECL clock drivers for the parallel DAC chips.

[Bernhard]

I had an idea to solve the DIY DAC master - transport slave problem universally.

The clock from the DAC can be transmitted using ECL logic without problems.
On the transport side, a retriggerable monostable multivibrator disables the transport clock for a duration of two or three pulses on every incoming clock pulse.
So there is no problem of running the transport without clock.

[EUVL]

While I admire you beautiful work, I think you would do us a real favour if you could post schematics with available components.
I don't think the 2SK152 is easy to source (obsolete), and I only managed to find out about the AD96687 by accident.
Unless of course you can help us with the sourcing as well .....



Patrick

[Bernhard]

AD96687 can be bought from Digikey.com for about 10 $.

The SK152 can be found in old Sony CD players, I think you can use the J309 like in the Kwak Clock instead.
There are other RF FETs too. Like SK120 and SK125, those even seem to be faster.
That could make it necessary to readjust the resistors 910 and 1k that set the supply voltages to about +2,5V and -2,5V.

The blue lines in the schematic that connect the left and right sides are optional and perhaps preferable, my clock has still separate supplies.

I will draw a schematic how to connect the ECL parts later.

[bordins]

Originally Posted by Bernhard

Can you enlighten me why that should happen ?

My apology. I misunderstood my friend's points.

Bernhard, where did you get the black cover above ?

[qusp]

Bernhard, great work and I must say i'm quite interested. the obscene prices charged for some other discrete clocks is prohibitive, well rather I refuse to pay them. anyway i'm keen, but i'm also quite interested in your teflon PCB, can you enlighten me as to how this process is achieved?? i'm designing a transformer output PCB for my sabre dac using lundahl iron, would love to make the PCB teflon

[qusp]

or is it just as simple as substituting a teflon board??

[Bernhard]

Originally Posted by bordins

Bernhard, where did you get the black cover above ?

It is from a transformer.