With dcs Scarlatti stack, I have run several rubidium clocks from a cheap and simple China Telecom surplus unit from eBay, up to Quartzlock module. All of the rubidium clocks are designed to output via an SMA connector to 50 ohms. In all cases, sound changed from standard Scarlatti clock, generally to produce a better imaging result. The 50 ohm SMA in some units just goes through a short jumper to a BNC connector.
Working on a project with Quartzlock, I had an opportunity to try any type of frequency standard. The advice of the Quartzlock engineers was to try the 8607 BVA ocxo because it had the best available results in phase noise. Initial tests were with a simple set up with a 24v switched mode supply and the same sma to bnc jump lead to a 50 ohm bnc on the rear panel. Connecting this to the Scarlatti clock with a 75 ohm cable produced a very good result.
Trying to get even better performance, I used a 50 ohm lead direct from the sma on the ocxo case to a 50/75 ohm converter at the dcs clock reference input. Again a noticeable change for the better.
Final upgrade was to build a high performance power supply and fit clock in a decent case with mechanical damping: results outstanding!
Cybershaft clock? I can't comment because I've not had the opportunity to try one although the specs look very good at a very attractive price.
The end of production of the BVA Oscilloquartz 8607 was a great pity however it was difficult to make because of low yields. I understand that there might be an alternative sometime soon but no firm details yet.
For me, the next steps are to do more work on optimising the 50 ohm cable.
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