Add 10mhz clock : sin wave or square wave?

Hi everybody,
I have a question vous external 10mhz word clock generator.
Reading Vivaldi Clock manual we can use a 75ohm external 10mhz generator. But it is not mentioned anything about waveform : sin wave or square wave.
Does anyone have an answer ?

What abut using a 50ohms instead of 75 ohms ?

Any suggestion of external clock that fits well with our dCS setup ?

It’s on Page 13 of the Vivaldi Clock Manual;

The “TTL” (Transistor-Transistor-Logic) is in reference to Square wave reference clock input signal, while the “AC” is in reference to a Sine wave reference clock input signal.

An impedance mismatch of a 50Ohms clock output to the 75Ohms dCS reference clock input is liable to work unpredictably, especially given the relatively high frequency of 10MHz, I expect there’ll be lots of reflections in the signal.


Thanks a lot ! :+1:

Do you know about a GPS receiver that matches dCS needs ?

You might find this thread interesting:

As a master clock, I think the dCS Vivaldi Master Clock is superb. It neither needs nor requires additional reference clocking to deliver excelrional performance. However . . . it does have that little jack on the back for connecting a reference clock. It’s pretty much an invitation for your wallet, right? :wink: The SRS Perf10 is a great place to start, as its design and performance are consistent with the some of the target characteristics (identified here in the forum by dCS engineers) that could theoretically provide additional clocking stability to the Vivaldi. Whether you can hear that stability is up to your ears and brain. I like the SRS a lot, though I sold it due to rabbit hole psychosis.


I’m glad the Rabbit Hole Psychosis spores weren’t still on it when it arrived. I’ve managed to stay with the Perf10…only adding the odd alert to HifiShark for even more wondrous reference clocking. Luckily none triggered yet :slight_smile:


Any GPS receiver which has a 10MHz 75-Ohms BNC output for frequency reference should work. They’re not all of the same quality obviously, so I wouldn’t expect just any GPS Receiver to benefit a dCS stack.

Alas, every now and then I go through the exact same malady and I start trawling eBay for Cesium Clocks. Fortunately, they’re usually too old, too bulky/noisy, or too expensive to be seriously considered :rofl:


You could always get one of these… They’re not much to look at but ohhh, the accuracy! ; )


I actually think thant’s kinda cool. Like @Anupc, I often go looking . . … But the Kronos remains “good enough.” For all practical purposes, a quality GNSS is essentially a cesium surrogate.


Agreed. And, from the article, I am reassured that there are still a couple people in the US who do high quality science/engineering:

“Once the evaluation is completed, NIST-F4 will contribute to UTC and calibrate the absolute frequency of next-generation optical atomic clocks. It is expected to reach an accuracy approaching the 10^-16 level in fractional frequency.”

; )


To think we put all this effort into getting clocks accurate to a billionth of a second and then we go and add or subtract whole seconds at a time messing the whole thing up :wink:

Here’s a recent tidbit;

About a month ago I watched Micheal Framer’s YouTube video of his visit to UMG’s tape vault at Iron Mountain’s underground limestone facility outside Pittsburgh.

When he was inside one of their “digitising” rooms, I noticed they were using an Antelope Audio Isochrone 10MHz Rubidium Clock (@ 1:18:55 min mark).

On paper, the specs of that thing are pretty good. A local friend of mine has one, so I asked to borrow it just for kicks. I replaced my (Mil-Spec SRS-based) 10MHz reference in my Vivaldi stack which has been in place for years with the Antelope…

Wow… subjectively, it was relatively speaking a day & night difference, and not in a good way!!

I couldn’t move fast enough to rip that thing out of my system. I think it actually made my system sound worse than just using the Vivaldi Master Clock’s internal reference on it own :man_facepalming:t2: