Rubidium Clock

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.

Correct in the case of the K-01X; it only has a WORD CLOCK IN connector which is 75-ohm (as with other Eso gear). It does not have a separate 10Mhz input.

In the way of an update, I have the Cybershaft Rb+OCXO 'dual master clock' offering up and running as of late and I am extremely impressed by the build quality of the unit and the customer service provided by Hasegawa-san at Cybershaft.  He goes to great lengths to ensure all questions are answered and provides unit-specific test data for ALL testing of the unit including Allen Deviation, reference measurement devices used, etc....It's the most specific and open backing of what a unit truly does after it is built I have ever seen.  The price point of the unit is a fraction of the other offerings in the space (that provide 10 Mhz atomic-precision master clocking) and frankly when I saw the unit, it's quality, appearance and sheer weight coupled with the exceptional customer service, I don't fee that I am missing out on a single thing compared to the offerings from Stanford Research, Isochrome/Antelope or others. I currently have this connected as follows;

Cybershaft Rb-output=>10Mhz=>Esoteric D02 (WRD CLK IN, 10Mhz)=>Esoteric P02 (MCLK frequency from the D02). 

Put another way, the Cybershaft clock is providing an atomic-precision baseline for the clocking circuit of the D02.

All the specs and other technical aspects aside, there was an immediate improvement in the natural/liquid nature of the sound when I enabled the 10Mhz input signal from the Cybershaft to drive the WRD CLK Input of the D02 over the D02 alone. All was extremely good before but I find a touch more precision in image size and placement (of instruments and voices) and an even more musical presentation overall of the system as a whole.

I am very happy to have stumbled on the company out of Japan that as it turns out produces alot of these and similar devices for broadcast and recording audio and video firms and audiophile users in Asia.  My hat is off to Hasegawa-san and his team for building on hell of a component at a fair price and topping that with some of the best customer service and attention to detail I have ever seen!