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Entreq "signal grounding" Preliminary Measurements

amirm

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#1
Hello everyone.

As some of you know, I signed up for making some measurements of the Entreq "signal grounding" box. If you don't know what that means, you are not alone :). It is a type of device where you connect it to the ground or negative terminal of your audio signals and it is supposed to improve the fidelity of the system.

I was given a loan an Entreq Olympus Minimus for this testing by the company founder, "PO."

The box arrived a few weeks ago but have been too busy to test it until now. From the outside, it is a nicely made wooden box with a single terminal out back:



The box is very heavy so clearly filled with something substantial. I was not allowed to open the box so my evaluation is limited to measuring it.

I had thought of measuring a lot of things but once I got to it, the reality set in. The box has only one wire going to it, not two. That is, there is no return path for any electrical signal. Think of trying to test a battery with a light bulb but being allowed to only connect one terminal! Obviously nothing will happen whether the battery is good or bad. Same here.

So right there, we are in a very small domain of electrical circuits. Namely, an antenna. That is the only construct I can think of where a single wire is connected to a piece of electronics.

I went ahead and made some measurements. The purpose of the thread is to get feedback on ideas/feedback from folks on it as I like to give it a fair trial. Once we feel good about the data, I will then post it on WBF where folks are waiting for the information.
 
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amirm

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#2
For measurement, I thought I go simple. My Audio Precision Analyzer which you see to the right of my desk below the Stax headphone amps has both an analog generator and analyzer. So I set up a simple test connecting the output of the generator to the analyzer. I then ran a THD+N test. This is a test where a 1 Khz signal is played by the generator. The analyzer has a filter at 1 Khz which sucks that tone out. Everything that is left is noise and distortion.

I ran the test two ways, without and with Entreq. Here are the results:

Balanced FFT 32k with and without entreq with overlay.png


The bottom two runs are without Entreq (yellow and red). I ran it twice to see how repeatable it is. You see a low noise floor of -150 db SPL with a notch at 1 Khz due to the filter and a few spikes here and there.

Addition of Entreq in Green hugely raised the noise floor by some 40 dB. So clearly we are injecting noise into the signal with this rather long (2 meter or so) cable.
 

amirm

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#3
For the next test, I used a very short, about 6 inch wire. Here are the results now:

Balanced FFT 32k with and without entreq short cable.PNG


Yellow is without Entreq and Red is with entreq. We see that the shorter wire induces far less noise into the signal chain. But it still does some damage in the form of all of those little peaks.

This confirms that the wire is acting like an antenna. The side that is connected to Entreq does nothing since it is a high impedance path to real ground. Shortening the wire made for a less good antenna so it is injecting less.
 

amirm

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#4
Wanting to see what happens with wider analysis bandwidth, I switched to a different FFT on the analyzer that gives me spectrum up to 130 Khz. I have also zoomed in vertically for this graph:

Balanced FFT 260k with and without entreq short cable.PNG


Yellow is again the baseline without Entreq. And Green is with entreq and short wire. We see new noise and distortion components added to the signal. There is no improvement in any part of the spectrum with the addition of Entreq. It is all degradation.
 

amirm

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#5
Next I fired up my oscilloscope and made three measurements. First is my scope tip connected to the negative signal terminal of the Analyzer output:
NO Entreq.jpg


There is some noise there as the scope is pretty sensitive and picking up the 60 Hz hum.
 

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amirm

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#6
Here is what happens if I leave everything the same but add the short entreq wire:

Entreq Short 6 inch wire.jpg


Without changing anything, we visually see increased noise induced onto the negative signal ground.
 

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amirm

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#7
This is what happens with my 2 meter wire:
Entreq long speaker wire.jpg


As we noticed in the frequency domain, longer wire clearly picks up more garbage from the air and pushes it on the signal negative. Nothing good comes out of doing this.
 

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amirm

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So that is it for now. Bottom line is that the device seemingly does nothing. The only measureable effect is the wire that goes to it. That wire acts like an unterminated antenna so picks up whatever noise there is in the vicinity and injects it into the signal path. Depending on what noise there is, and how the equipment behaves, there may be little to a lot of noise injected.

In all respects, this device and connection seems to be detrimental based on these measurements.

From audibility point of view, I think the scheme is benign if the noise levels stay at what I have measured.

All feedback is appreciated :).
 

RayDunzl

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#9
Allow me to play Devil's Advocate:

"Well, you didn't operate the Entreq as designed.

Please read the manual."
 
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#10
Wow that manual is really well written! :rolleyes:

Note. Since all our connectors are made of wood for eliminate all kind of stay volts, magnetis, e,t,c and the fact that is vary a lot on the width of RCA outlets, you need to take it gentlry when use our
Entreq Manual Groundbox RCA plugs.
 

amirm

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Allow me to play Devil's Advocate:

"Well, you didn't operate the Entreq as designed.

Please read the manual."
I had actually read the manual. As you can see, there is little in there.
 

amirm

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#12
Forgot to post this other measurement.

I have a very sensitive micro-amp clamp meter. It is designed to measure leakage current to the ground of equipment. It is a unique piece of equipment. As an example, it shows a 60 microamp leakage on my amplifier power cord.

I put the clamp on the longer wire I measured in the first test. This is what it shows:

20160503_154427-cropped.jpg


Yes, nothing. This means if there is current flow to/from Entreq, it is below 10 millionth of an amp.
 

RayDunzl

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#13
Yes, nothing. This means if there is current flow to/from Entreq, it is below 10 millionth of an amp.
Within the frequency range of the meter, so, up to 3kHz (probably higher, but undefined).

---

You haven't tested it on a noisy ground yet, from what I can see.

It increases the noise on a quiet ground, but does it quiet a noisy one?
 

John Kenny

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#14
Within the frequency range of the meter, so, up to 3kHz (probably higher, but undefined).

---

You haven't tested it on a noisy ground yet, from what I can see.

It increases the noise on a quiet ground, but does it quiet a noisy one?
Tut, tut - are you measuring the measurist?
 

amirm

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#15
You haven't tested it on a noisy ground yet, from what I can see.

It increases the noise on a quiet ground, but does it quiet a noisy one?
So far the results indicate "it" does nothing. It is a very high-impedance termination of the wire. Everything I am measuring is the results of what rides on an unterminated wire. The fact that entreq is at the end of it or not is invariant.
 

Dynamix

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#16
Wow that manual is really well written! :rolleyes:

Note. Since all our connectors are made of wood for eliminate all kind of stay volts, magnetis, e,t,c and the fact that is vary a lot on the width of RCA outlets, you need to take it gentlry when use our
Entreq Manual Groundbox RCA plugs.
:D

Lol, nice "Swenglish". Speaking as a Scandinavian myself, the fact that these guys weren't even able (or couldn't be bothered) to find someone to proofread their marketing material speaks volumes about this company.
 

John Kenny

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#17
Within the frequency range of the meter, so, up to 3kHz (probably higher, but undefined).

---

You haven't tested it on a noisy ground yet, from what I can see.

It increases the noise on a quiet ground, but does it quiet a noisy one?
Yea, can't you see that meter reads ZERO - what more "proof" do you want with your impertinent questions?
 

RayDunzl

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Yea, can't you see that meter reads ZERO - what more "proof" do you want with your impertinent questions?
Much of my career, such as it was, was to not take 'yes' OR 'no' for an answer, but to keep poking around till something interesting occurred.

It is a unique piece of equipment.
What makes that leakage tester unique?
 

John Kenny

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Much of my career, such as it was, was to not take 'yes' OR 'no' for an answer, but to keep poking around till something interesting occurred.
That sort of thing will create enemies, don't you know, you rapscallion?

What makes that leakage tester unique?
Because it's designed to measure mains frequencies & their harmonics & Amir is using it in a "unique" way other than what it was designed for.
 

amirm

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#20
What makes that leakage tester unique?
a) it measures microamps
b) does not get false reading by stray fields around it

Once you make the device sensitive, it can pick up so much garbage and show such inconsistent results that the device becomes useless. This one is amazing. You close the clamp and it zooms right in to the right value over a few seconds and then it doesn't change.

To show you how sensitive it is, the moment I took it off the wire the jaws got close to the Audio Precision and it immediately faulted and shut down due to overflow! It was still inches from the chassis and not close to any wire.

Importantly, it is designed for this exact use: i.e. measuring ground currents/leakage.
 

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