Anyone have a believable answer to this???

[rocky500]

On 31/05/2019 at 9:16 PM, Ittaku said:

I've got a powerline EMI noise meter. It's "noisy" all day long on weekdays and then abruptly drops after 6pm to about 1/4 as much. This is repeatedly demonstrable. I haven't checked whether weekends are any better. Whether this translates into audible noise after the entire audio chain is something I haven't a means to measure, but I don't particularly hear a difference with my system. I suspect the power supply design of components comes into play and mine are fairly heavily over-engineered on that front.

 

 

Just got one of these today, thanks Ittaku.

Quick plugin right now and it is 1400s to 1500s in one power point. Plus I can hear a radio station faintly in the background.

Plan to try it out with my stereo system with the different times of day/night.

Tuesdays seem to be the day for me, when my stereo sounds the best. 

Will be interesting to see if it relates to a lower number that day.

 

 

 

ADDED:

Here is my other powerpoint my Stereo comes off. I had a separate dedicated line put in to the room when I renovated the room.

We have 3 phase coming into the house for the old 3 phase hot water systems, oven etc.

Electrician put the room on a different phase to what the other power points in the house were wired too.

 

 

Edited June 14, 2019 by rocky500

[t_mike]

I'd like to see the measurements taken though a standard power cord versus an expensive one.

[Ittaku]

1 hour ago, t_mike said:

I'd like to see the measurements taken though a standard power cord versus an expensive one.

From the EMI noise meter? It reads identically, of course.

[rocky500]

12 hours ago, t_mike said:

I'd like to see the measurements taken though a standard power cord versus an expensive one.

Ordered one of these just now to see if changing cables makes any difference to the device. LINK

 

This morning. House powerpoint 1750/240V (no radio station head this time) & Stereo powerpoint 780/247V

Edited June 15, 2019 by rocky500

[rocky500]

Just tried plugging into my balanced transformer. It is wired to drop the voltage a little too. Everything in my stereo runs from this but my Amplifier.

 

Edited June 15, 2019 by rocky500

[Ittaku]

4 minutes ago, rocky500 said:

Just tried plugging into my balanced transformer. It is wired to drop the voltage a little too. Everything in my stereo runs from this but my Amplifier.

Transformers are an excellent way of getting rid of noise... but remember every regular power supply has a transformer too

[rocky500]

4 minutes ago, Ittaku said:

Transformers are an excellent way of getting rid of noise... but remember every regular power supply has a transformer too

I thought there was also a advantage having a balanced transformer. Gets rid of more noise?

 

https://www.tortech.com.au/custom-transformers/balanced-transformers/

Edited June 15, 2019 by rocky500

[Ittaku]

3 minutes ago, rocky500 said:

I thought there was also a advantage having a balanced transformer. Gets rid of more noise?

Honestly, I don't know, but you are putting another transformer in so it's bound to get rid of more noise since they're now sequential. Whether that further noise reduction translates into a performance or quality advantage is still unclear though without measuring what happens at the final endpoint to the sound.

[frednork]

7 minutes ago, rocky500 said:

I thought there was also a advantage having a balanced transformer. Gets rid of more noise?

 

https://www.tortech.com.au/custom-transformers/balanced-transformers/

same idea as a balanced cable, high level of noise rejection as shown in your measurements.

[frednork]

12 minutes ago, Ittaku said:

Transformers are an excellent way of getting rid of noise... but remember every regular power supply has a transformer too

Are they balanced though....

[MLXXX]

 

1 hour ago, frednork said:

Are they balanced though....

In the sense provided in the following explanation for the operation of @rocky500's balanced transformer, yes:

 

How does it remove power line noise?
Transformers only respond to voltage differences between their leads.  Power lines often have a type of noise called common mode noise which is present on both the neutral and hot wire.  The Balanced Power Supply contains a massive toroid transformer that reject [sic] much of this noise.

 

 

A mains transformer in audiophile equipment for use in Australia will galvanically isolate the secondary from the primary. There will be no direct connection from the mains neutral to the equipment itself, only to the primary winding of the power transformer.  So if there happens to be common mode noise on the incoming active and neutral lines, that  should cancel itself out in the primary winding of the power transformer. [Whether any of it might pass through by capacitative coupling to the secondary winding would be a separate issue to consider.]

Edited June 15, 2019 by MLXXX

[MLXXX]

1 hour ago, rocky500 said:

I thought there was also a advantage having a balanced transformer. Gets rid of more noise?

 

https://www.tortech.com.au/custom-transformers/balanced-transformers/

Here's an interesting claim on that webpage:

 

By eliminating reactive current in the earth, this lowers the studio noise floor, extends frequency response and improves stereo imaging.

 

In Australia our audiophile equipment doesn't involve a connection from neutral to earth, so there'd be no reactive current in a single connected appliance arising from slight differences between neutral and earth at a power point. [And if our audiophile equipment is earthed, we can't go substituting a pseudo-earth. That seems likely to be illegal.]

 

But just for the sake of argument, let's focus on the possibility of there being some sort of earth loop "reactive" current between two items of interconnected audiophile equipment. Can someone provide a specific example in practice of that, or anything similar to that, "reducing the frequency response". If possible, please give details of:-

• the equipment affected (e.g. brand, model)
• the number of dB by which the frequency response was curtailed and over what range of frequencies the curtailment was found to occur.

I don't really expect anyone to be able to provide a concrete example. But if there is such an example available, could someone please provide a technical explanation as to how the measured reduction in frequency response was triggered by "reactive current in the earth"?

[Ittaku]

2 minutes ago, MLXXX said:

By eliminating reactive current in the earth, this lowers the studio noise floor, extends frequency response and improves stereo imaging.

I suspect these are subjective audiophile/hi-fi observations and not demonstrable measurable quantities.

[frednork]

@rocky500,  is it possible to measure the emi post transformer in a piece of equipment with and without the balanced transformer?

[rocky500]

50 minutes ago, frednork said:

@rocky500,  is it possible to measure the emi post transformer in a piece of equipment with and without the balanced transformer?

Not sure exactly what you mean. 

I plug into the powerpoint on the wall, it is a 4 gang. the meter reads 930 right now. The balanced power supply is plugged into that same powerpoint on the wall in one of the other ports.

Plugging meter into the output of the BPSU it currently reads 77 on the meter. If I turn on the 65" LCD the meter jumps to 400 still plugged in the BPSU. The wall remains the same with and without TV.

The balanced supply has 3 outputs. 2 are used to different power boards that all my stereo gear is connected too and one is free.

Edited June 15, 2019 by rocky500

[frednork]

3 minutes ago, rocky500 said:

Not sure exactly what you mean. 

I plug into the powerpoint on the wall, it is a 4 gang. the meter reads 930 right now. The balanced power supply is plugged into that same powerpoint on the wall in one of the other ports.

plugged into the BPSU it currently reads 77 on the meter. If I turn on the 65" LCD it jumps to 400 plugged in the BPSU. The wall remains the same with and without TV.

The balanced supply has 3 outputs. 2 are used to different power boards that all my stereo gear is connected too and one is free.

Well the guys here have basically said that the transformers in hifi gear provide reduction in emi so I am suggesting is it possible to get an amplifier  or something similar , open it up and safely measure it at the output of the internal transformer and then plug  it into the BPSU and compare.

[MLXXX]

52 minutes ago, Ittaku said:

I suspect these are subjective audiophile/hi-fi observations and not demonstrable measurable quantities.

I could imagine that actual very low level noise could be measurably reduced; though whether that would be of high enough level to be audible above noise in a recording or in the listening environment would be other matters.  

 

As for "audiophile noise floor" that appears to be something of its nature restricted to audiophile/hi-fi subjective observations. It is not something we see quantified in decibels.

 

I chose "frequency response" as that is something definitely capable of being measured, but if measurements of "frequency response fall-off" triggered by "reactive current in the earth" have proved elusive, ah well, that's the audiophile world for you! No surprise in that.

[Ittaku]

3 minutes ago, MLXXX said:

I chose "frequency response" as that is something definitely capable of being measured, but if measurements of "frequency response fall-off" triggered by "reactive current in the earth" have proved elusive, ah well, that's the audiophile world for you! No surprise in that.

Indeed, but I think in this case the 'extended frequency response' is that perceived benefit where you get more top end or bottom end, rather than the actual measurement of frequency response.

[MLXXX]

2 minutes ago, Ittaku said:

Indeed, but I think in this case the 'extended frequency response' is that perceived benefit where you get more top end or bottom end, rather than the actual measurement of frequency response.

Exactly. A perception one has, knowing that the special transformer is in place.  Not anything successfully measured.

[Ittaku]

Having said that, I've certainly made changes to hi-fi components that seem to extend the bass lower or the top end higher and don't measure any differently in sweeps, but they are also changes discernible in blinded tests, so something else is adding to that perception of extension, be it phase, timing, distortion, or dynamic response that won't show up in a simple sweep.

[MLXXX]

45 minutes ago, frednork said:

open it up and safely measure it at the output of the internal transformer

The rectifying diodes feeding the resevoir capacitors could create discontinuities in current flow that might read as EMI depending on what type of measuring device is used. An approach that might work would be to disconnect the secondary winding from any load.

 

If really keen on taking measurements it might be more meaningful to measure ripple at the resevoir capacitors, under load, and ascertain how much high frequency "hash" is present there. It should be quite minor.

 

Going further and attempting to measure "hash" after voltage regulation and further filter capacitors could be problematic as it could be unmeasurably low.

 

Another issue though is that mains borne EMI may not be common mode in the first place, or if common mode to some extent it might not be exactly in phase as between active and neutral.

 

Another thing to consider is the extent to which any small DC offset in the mains supply could be reduced by interposing a "balanced transformer". Some people have had audible hum/buzz that they attribute to DC offset in the mains supply.

 

Edit: Yet another question, and this occurred to me earlier but I didn't raise it, is: what voltage reference(s) does the EMI measuring device use?  In taking measurements does it float with respect to earth? Or does it measure active to earth, and then neutral to earth, as separate readings? Does it already reject common mode EMI as between active and neutral?  I haven't bothered to chase those matters up by looking at specifications and user manuals, etc, but hopefully someone here can give some answers off the top of their head.

Edited June 15, 2019 by MLXXX

[Ittaku]

I believe the EMI measuring device subtracts the mains frequency its powered with from the mains signal and audibly amplifies anything else, and measures mains and remaining voltage. There's a *small* chance it works in a generalised way enough that you could touch its terminals across the output windings from a component's transformer and get a meaningful result, but I suspect the voltage would be too low for it to work properly.

[MLXXX]

On 31/05/2019 at 11:16 PM, Ittaku said:

I've got a powerline EMI noise meter. It's "noisy" all day long on weekdays and then abruptly drops after 6pm to about 1/4 as much. This is repeatedly demonstrable. I haven't checked whether weekends are any better. Whether this translates into audible noise after the entire audio chain is something I haven't a means to measure, but I don't particularly hear a difference with my system. I suspect the power supply design of components comes into play and mine are fairly heavily over-engineered on that front.

 

I see a description and specs for the above, on the net, as follows:

 

Description：

The Line EMI Meter measures electromagnetic interference in a single-phase AC power line. It plugs into a wall outlet (mains socket) and requires no battery. It immediately displays total line noise in millivolts (range 1999 mV, resolution 1 mV) in the frequency range 10 KHz – 10 MHz (the frequency limits at which sensitivity is ½ of the maximum sensitivity). A speaker plays the sound of the EMI, amplitude demodulated, in order to identify the EMI source (such as an AM or shortwave radio station vs. a motor vs. an electric arc).

SPECIFICATIONS: Line EMI Meter Model PLM

Operating Voltage: 85 – 250 VAC 50/60 Hz.

Voltage Reading: 85-250 VAC; Accuracy +/- 1 VAC

Line Noise Range: 1-1999 mVAC (differential)

Line Noise Accuracy: +/- 5% @ 1 MHZ; +5% to -50% @ 10 KHz TO 10 MHz

Size: 5.2 x 3.6 x 1.6 inches; 132 x 91 x 41 mm

Weight: 225g

Power Cable: Detachable 2-wire cord (appropriate to country)

 

______________

 

The above answers my question as to whether the meter already rejects common mode EMI. It does (as I've highlighted in bold red).

[rocky500]

Here is some of the times I checked the meter.

Seems it may line up a bit with what I hear, so could possibly be related. Then it could be something else too but seems to correlate. Could also mean mornings/evenings are better with less EMI on the line?

Need more data points.