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Comments on your post (sorry - a bit long)

Posted by Ryelands (A) on January 27, 2017 at 09:37:32

In Reply to: Indeed: very marked SQ improvement! Thank you for sharing ! (NT) posted by hfavandepas on January 27, 2017 at 08:02:28:

Indeed: very marked SQ improvement!

Thanks for the feedback. Are you using decent cable/plugs? Have you done every possible cable? If not, you may well have further improvements in store. Meanwhile, as promised, comments on your earlier post.

It highlights a 'hidden' problem that I also had in my system

WRT the Juergen Reis interview, I'm not sure you're right to suggest that "these 'back door leakage currents' are also better known as: ground loops". My take was that by "back door noise" he meant how different PSUs in the same system tend to interact with each other in ways that the spec sheets don't (can't) describe even when properly configured that nevertheless degrade the sound. Ground loop issues are well understood even if tackling them can - as you've found - be time consuming.

John Swenson makes a similar point on the Uptone Audio web site - see link. He suggests that:

There are two methods by which a power supply interacts with the AC mains and the difference is not well understood by most people (even many engineers). The solutions to deal with them are very different but get all jumbled up in most peoples minds [snip]:

1) noise between the hot and neutral (and maybe ground wire)
2) leakage current between the AC line and the DC output of a PS

#1 is pretty straight forward and what most people think of when they talk about "noise injected into the mains". There are many types of filters, power conditioners etc that deal with this.

#2 seems to be much harder to understand. It is created by the power supply, some of the AC voltage on the mains sneaks through parasitic capacitances in the PS and winds up on the DC output. The strange thing here is that it is between the the AC line as a whole (hot, neutral, GND) and the DC output as a whole (+, -). It does NOT exist between hot and neutral or between the DC - and +. It is between the two groups.

Because of this any type of normal AC line filter or DC filter or regulator is completely useless at combating this. All these devices work by "filtering" the noise between hot and neutral or between + and -. But this type of noise does not exist that way.

Later, he advises folk to take any filters for "type 1" noise out of their systems and instead connect everything via a multiplug to a single mains socket. I can't comment on how well that works but I can say that the Swenson-designed LPS-1 "Supercap" PSU which I'm currently using to power the DAC end of the fibre optic (and gubbins) link between my system's audio PC and its server transforms (sorry) the SQ of my system.

BTW, every other box in my system except the amp connects to the mains via a Jon Risch-style DIY mains isolator (i.e. the audio PC, an Intona, the USB> I2S board, the DAC and the DAC's I/V section, five devices (ten transformers and 15 coils . . .) all told. A transformer good enough to isolate a power amp is too expensive. I don't know if the isolators are dealing with "back door noise", "Type 2 noise" or just noisy neighbours but I do know that if I take them out there is a dramatic drop in sound quality. I'm hoping soon to get a second LPS-1 for the PC.

I feel pretty sure it's not ground loops I've cured as discussed in the Jim Brown or Bill Whitlock papers as I have no connections between system ground and safety ground. (There are safer ways of keeping them separate BTW so don't take this as a tip even if I got it from a Charles Hansen post a while back.)

Finally, though removing redundant pairs from my LAN cables also makes - as you've confirmed - for a jump in SQ, it is definitely not because it fixes a ground loop issue. LANs use differential pairs that have no ground; LAN sockets always come with an isolating transformer and I have in any case two in-line medical-grade isolators not to mention that pesky ground-free LPS-1 PSU. My guess would be that removing the wires (and running at 10-BaseT) does wonders for Near-End Crosstalk on the spare pairs. But it's a guess. What's not a guess is that it was an effective tweak.

HTH

Dave

• Swenson goes to ground ?   (Open in New Window)

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