Hi Greg:
Sorry to have insulted you. Certainly not my intention! And thank you for your purchase of an EtherREGEN.
The EtherREGEN is not an ordinary switch, and its goals, methods, and the ideas underpinning it seem to attract both detractors and misinformation. My response was prompted by incorrect notions about the clocking system of the EtherREGEN.
To be clear:
a) Like virtually every computer/digital product, an Ethernet switch requires a clock. This is of course a data clock, entirely unrelated to DAC audio clock frequencies.
b) For various reasons (explained in our paper) we have determined that both the quality and the handling of this clocking is critical. We go to extraordinary lengths with clocking in the EtherREGEN, using techniques (such as LVDS clock lines and expensive, 10GHz-capable ultra-low-jitter flip-flops) that even surpass what is in most DACs (though I hope some of the upper-end dCS units have something similar).
c) Because we need 4 clock lines (two at 25MHz and two at 250MHzâfor the logic chips and flops on both sides of the differential isolation âmoatâ), we use a jitter-attenuating Silicon Labs clock synthesizer to produce those four LVDS clock lines. Our normal reference for that synth is an ultra-low-phase noise Crystek CCHD-575 that we order custom at 25MHz. Short of a $400 OCXO (cheap OCXOs donât equal the phase-noise/jitter performance of the $10 Crystek 575) thatâs the best production XO to be had.
d) The Silicon Labs clock synthesizerâsitting just millimeters from the most critical logic chipsâhas 4 outputs and 2 inputs (inputs being for clock it is referenced to). We program the clock synth in house (its outputs, its inputs, and other parameters). We connect the Crystek 575âitself just 2mm from the synthâto one of its inputs.
e) Given that some audiophiles like to play with external reference clocks, and that a near 3x our price competitorâs switch can be ordered with an external clock input (for an extra $250), we thought why not spend an extra $3 on a BNC jack and offer that second synth input for optional use with fancy 10Mhz reference clocks.
It is not something we promote as required, but some people are using it and reporting modest further SQ gain (nowhere near the benefit of just the basic EtherREGEN with its already excellent internal reference clock). [Similarly with power supplies: We spend a TON on the internal power networks, and our switch sounds great with just the custom SMPS we include. But offer a device that runs from external DC and enthusiasts are going to end up experimenting and reporting about it with various fancy linear supplies. And thatâs fine. We happen to produce a couple models of highly regarded LPS. But I donât promote them for use with the EtherREGEN because to me great power supplies are more important elsewhere in a system.]
I am still rather confused about where the comments about our saying anything regards âsynchronizing clocking with the DACâ come from.
There is no direct relationship between the clock in the switch and the clock in the DAC (or computer, etc.). There are however effects of ground-plane noise and phase-noise on the ground-plane of an Ethernet input receiver (in the dCS world your Ethernet-input DACs), and those somehow (see our paper) do cause enough disturbance to affect the 0-volt plane by the clock pin of the DAC chip. And that is why people hear a difference with our device (and similar).
Iâve definitely gone on long enough here. I am not the engineer here (John Swenson is) and donât have all the answers. And we have been upfront that the EtherREGEN was designed based on theories about the underlying mechanisms of all this and Johnâs vision of how to best directly solve the matter with new chips and a unique and costly design. He continues to work on assembling the highly sensitive test gear needed to produce visual/graphical proof (both for the skeptics and for future development work). We just bought a $15K Jackson Lab PhaseStation and he is building special boxes and power supplies to support the test rig as environmental disturbance adds distracting turmoil to the measurements.
Thanks for reading.
Goodnight,
-Alex C.