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In Reply to: RE: 'back door leakage currents' = ground loops (very, very looong post) posted by fmak on January 26, 2017 at 18:47:32:
"But which is the chicken and where is the egg?"
Good Question !
Lets consider the chicken = noise source.
The eggs = the noise flow.
First off: The noise source (chicken) does not necessarily needs too be the Sonore Signature PSU.
There may be other noise source candidates along the loop.
Also: system parts that suffer from common noise traveling on the circuit board may be more than 1. The microRendu may suffer, the USB data transport may suffer, the DAC may suffer.
Lets trace the noise flow first (follow the eggs).
When doing so it must be considered that current ALWAYS needs too return to it's source.
So which return path can be used by the noise too travel back?
Is differential mode noise?
(In one wire the noise flows 'up', in the other wire the same noise flows 'down').
Lets hope it is common mode noise.
I don't like too think of an 1.400 dollar Sonore Signature PSU that generously produces differential mode (U)HF noise.
Or is it common mode noise?
(Both wires same noise, same voltage, in same direction).
What direction is the common mode noise flowing?
Towards or from the microRendu?
All I know about Mercman's system is:
? -> Signature PSU -> 2 PSU wires -> microRendu -> USB cable -> Ayre QX-5 Twenty -> ?
? -> UTP LAN cable -> microRendu
- Mercman's friend put's an impedance Z (AC resistance varying according to frequency) on both PSU wires by means of a ferrite choke.
- The PSU wires are between the microRendu mini-pc and the Sonore Signature PSU.
- The impedance on the PSU wires reduces/suppresses the flow of (U)HF noise in the PSU wires
- Mercman enjoys better sound quality.
When trying too find the electrical return path for the common mode noise, I will have too drawn a circle that always includes:
A: the Signature PSU -> 2 PSU wires -> the microRendu
(no matter if the common mode noise is flowing towards or from the microRendu)
B: And the (U)HF noise source. This not necessarily needs to be the Signature PSU.
When trying too draw a circle that closes a loop, it is easy too see this only can be done through:
Circle A: a loop via the USB cable + power cords attached too system parts
Circle B: a loop via the LAN cable + power cords attached too network equipment and systems parts.
Suppose the noise travels back using circle A.
* Bridging the gap.
May be Mercman could also offer an alternative path for the noise too flow along in an attempt to bypass the circuit board inside the microRendu.
He could try too connect a wire between the PSU casing and the microRendu casing. It might work. But also it might not work and even making things worse by creating an extra loop.
All depends on where the noise source is located and if there is also a 'Pin 1'-type of design flaw present in any involved equipment.
* Hunt for another stick on plaster.
Most likely you are right about this.
Because the common mode noise needs an opportunity to get onto a power cord and travel back through the electrical system too the Sonore Signature PSU too close the loop .
Common mode noise on PSU (ref grnd) wire -> (ref. grnd) circuit board microRendo -> (ref. grnd) wire USB cable -> (ref grnd) circuit board DAC -> etc
Somewhere along this route it has to get on a power cord and travel back too the Sonore Signature. It might use the parasitic capacitances between the power line and the equipment ground for this. But it may also exploit yet another design flaw for this.
Mark
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- hunt for another stick on plaster - hfavandepas 07:54:24 01/27/17 (0)
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