+1. There are folks, Linn among them, who understand and can implement SMPS successfully.

There you go:

https://www.audioaficionado.org/showthread.php?t=46945


And here:

https://www.audioaficionado.org/show...t=47023&page=2

bart, thanks for the links.

The question is, are these SMPS sending high-source impedance leakage current downstream?

Does Linn even know to measure high-source impedance leakage current?

(it's not obvious how to do this...)

But Stephen, is it relevant if the sound quality is exceptional and noise level inaudible? It’s the end result that matters. Measurements are important, but they never tell the whole story. In the end it’s whether and how they impact the listening experience.

Reall good points, Tony, and I agree with you. Measurements don't always tell the whole story.

Back in the day, lots of folks thought that transistors amps had "exceptional sound quality" and were superior to tube amps. But wait..why did I find a Dyna ST-70 to be more enjoyable and engaging than an H-K Citation 12?

So, what we thought of as "exceptional sound quality" is, we've found over the last 40years or so of high-end...is continually evolving.

We still have folks that believe that with respect to digital music, that "bits are bits", its just 0s and 1s; there's no way that an Ethernet cable (used to be USB cables, remember?) can impact sound quality. We now know this is to be B.S. And, it's not 0s and 1s in digital music reproduction; its analog voltages. We've found that "perfect sound forever" is simply not true.

The impact of high-source impedance leakage current causes increased noise on the ground plane, increased threshold jitter and timing errors in the flip-flops and PHYs in endpoints and the DAC chips themselves, and in the digital domain, timing errors in the nanosecond range is audible. High-source impedance leakage current are an intrinsic failure mode from SMPS.

For an in-depth white paper on this by John Swenson, who designed these digital chips in his professional career, check out this white paper: https://tinyurl.com/yylwak9b

Quoting John Swenson: "Most all network systems used with audio use switching supplies (SMPS) to power the digital devices, routers, switches, computers, etc. The high-source-impedance leakage current from the SMPS will travel through the network equipment, the Ethernet cables, the end-points, and into the DAC where they will create noise on the ground-plane, and thus jitter in the DAC circuitry. Leakage currents can also cause clock modulation in intermediate devices such as “streamers.”

I'm asking a really simple question: do they know about this failure mode from SMPS and are they mitigating it? Are they even measuring it? Because how to meausure it is not obvious, nor is it easy to do. And, it does have an impact on digital music reproduction.

Jeff Rowland uses SMPS in most of his amplifiers including his flagship. My personal experience is even his entry level amps are quieter than many amps using linear PS. Like many things in this industry, quality materials and implemention is key.

Stephen, I really don’t have an answer to your question, I don’t know if Linn is measuring leakage current. They have published a fair amount of information on their power supply designs which can be found through an internet search. I’m also sure Linn would respond to the question if asked. Having said that, I’m afraid the technical aspects are a bit beyond my grasp, I only know what I hear and what others have reported hearing - their systems sound great. Whatever they may or may not have done about measuring and addressing leakage current, either they’ve addressed it effectively, or it doesn’t have a meaningful impact in their equipment, or the other advantages they have created with their design offset it.

All really good points, Tony. I fully acknowledge that this is pretty darn complex stuff; I had a to spend a lot of time studying and learning about it when I had to write the EtherREGEN review for TAS. It's...complicated. It took me a lot of reading and re-reading to get my head 'round it as I am not a digital signals processing engineer. I spent a lot time reading about what a flip-flop is, and how it can impact audio performance. :p

My personal view is, that with many "noise components", we often don't know they are there until they are gone. Just look at the work that Caelin and Shunyata have done over the last 20+ years to completely change and inform everyone's understanding about the impact of noise on our audio systems.

The reason I'm asking about (more like harping on) high-source leakage impedance current is that 1) it was only discovered in Oct. 2017 by John Swenson and 2) John had to develop bespoke, very specialized, test equipment, even to measure it. It's clear from the work John and Uptone have done with the EtherREGEN that it's impact on audio quality is significant.

And, I'm just asking EvaAnna, Bruno and Linn...do they even know about it? If not, they should, and, IMHO, they should be measuring it.