Rubidium Clock

Thanks for the great info. I will need to try one of those.

I've done a lot more research in this regard and have had a number of conversations with SRS as well as other options. The lead-time on the PERF10 or FS725 is longer than I would like to wait personally and my RFQs out to LibertyTest, AllTest and other certified/used equipment vendors for a PERF10 or FS725 have come up dry at the present time. I stumbled on Cybershaft Japan as an option via listings on various sites. It seems they make OCXO, Rudidium-only and OCXO+Rb clock units (single port each standard) for high-end audio, video and studio purposes at an extremely aggressive price point (the Rb-only unit is about $1300-$1500 USD depending upon JPY->USD conversion rate). They are rated for 100-120V and 50-60Hz use which makes them perfect for US or Japanese usage. The Rb-only unit has a single FIFTY (50)-ohm BNC clock output; they supply all their test and calibration results with each unit plus a 1 year unconditional warranty.  I have taken the plunge and ordered one as of yesterday; this should be a very nice and affordable test.  I plan to use this 10Mhz reference clock sync to drive my Esoteric D-02's clocking baseline while leaving the D-02 to sync itself and the P-02 transport together at 22.5792 Mhz.  This should surpass the already great performance of the D-02 clock circuit by a clear margin.  Unlike the PERF10 or particular FS725, this Cybershaft unit seems to have a better internal PSU but I'm not discounting the potential move to another HDPlex power supply with a retrofit in the future to get an even better bespoke PSU to drive the Rb-clock.  I will report back and let you know my findings between mid-late April after I receive it and break it in.  They state specific compatibility with Esoteric D-02, D-03, D01, G-01, G-02, G-03x, G-02s, K-01, K-01X, K-03 and K-03X.  You may read more here (use Google Chrome and let it translate the page);

www dot cybershaft dot jp

There are many relatively inexpensive scientific instrument versions with 50 ohm outputs. I could find none with a 75 ohm output, as needed for optimal impedance match with 75 ohm digital audio input as used on the Esoterics. Through a web search I found posts and screen shots by an engineer who measured a degraded 10Mhz waveform caused by reflections between mismatched 50 & 75 ohm BNC impedances. That was enough for me to pony up the added $$$ for the SRS.

The 10Mhz inputs on the Esoteric gear is spec'ed at 50-ohm, not 75-ohm. The "WORD CLOCK" In and Out BNC connections on Esoteric gear is spec'ed at 75-ohm.  Put another way, if you use an atomic/other external clock standard to supply a 10Mhz pulse, Eso gear expects that at 50-ohm whereas for Word clock purposes (44.1, 88.2, 176.4, 22.5792Mhz), they expect 75-ohm...

The K-01X manual specifies the BNC clock input as 75 ohm impedance.  I can't speak to other Esoteric products.