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Condition of our mains supplies

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Condition of our mains supplies

Postby ef37a » Tue Feb 26, 2019 3:34 pm

I read almost weekly of the "dirtiness" of mains supplies and it gets blamed for all kinds of ills affecting audio equipment both audio and digital.

Now admittedly many of the stories originate from the US which is of course vast and diverse and one can expect some "problem pockets" but I wonder what the experience of the SOS fraternity is?

The BELIEF I read about, from UK users as well, is that our supplies are dirtier than they were 50yrs ago. I would dispute that. I have memories of the 60's of trying to keep fridge splats out of the emerging audio gear. Radio grams and music centres as these things became transistorized.

I no longer get out and about doing audio but my experience here at NN5 5P* is that of zero problems, not even had a brown out in years. There is of course the fact of mains borne networking and Smart Meters* but surely these signals are at a level ref 230V and a frequency that they should easily be stopped by the most basic of filters?

*And surely these do not send continuously? The data load is miniscule so I would think the utility company pings, meter pings back?

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Re: Condition of our mains supplies

Postby blinddrew » Tue Feb 26, 2019 4:22 pm

I suspect there's a lot of variation depending on where in the country you are. Where I am in York I can recall about two power cuts in 18 years and no brown-outs.
Where my parents are, in North Norfolk, both are still fairly regular (at least once a quarter).
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Re: Condition of our mains supplies

Postby Luke W » Tue Feb 26, 2019 4:40 pm

Also Northampton here (or just outside) and it's always well behaved. There's rarely a power cut, and when there is it's usually a fairly local problem that's more likely to have been caused by a farmer digging somewhere they shouldn't or a tree falling over than a problem with the grid. I can only recall one brownout the whole time I've been alive.

I've encountered a lot of problems with audio systems through work, some of them doing some very strange things, but it's safe to say that the power itself couldn't be blamed for any of them!
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Re: Condition of our mains supplies

Postby garrettendi » Tue Feb 26, 2019 5:25 pm

Down here we usually get a power cut about every 2-3 years usually while I'm out the house. The only reason I ever notice the power cut is usually because my mains powered alarm clock is flashing, and on calculation the cuts are normally around 10 minutes long.
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Re: Condition of our mains supplies

Postby James Perrett » Tue Feb 26, 2019 7:10 pm

People don't listen to AM radio or watch analogue TV so much now so they wouldn't be as aware of interference issues as they used to be. In the days of 405 line TV there was no way us kids could watch Blue Peter while mum was hoovering.

We rarely have any problems with our power supply here - just the very occasional brownout in high winds, thunderstorms or during the worst of the recent snow.
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Re: Condition of our mains supplies

Postby Wonks » Tue Feb 26, 2019 7:35 pm

CE marking for electrical noise level reduction has certainly helped. Apart from damage during building/maintenance works, most electrical power losses are normally in areas that still have overhead power supplies.
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Re: Condition of our mains supplies

Postby ef37a » Tue Feb 26, 2019 7:52 pm

Thanks chaps. Now although I did mention "brown outs" my question was really about noise on mains feeds and whether people were experiencing much trouble in that regard?

As I said, some folks seem to be getting problems, or at least they seem to blame the mains supply whenever anyone posts a problem related to noise.

My feeling is that mains borne noise is not nearly such a problem as it is often made out to be (despite it being pretty impossible now to buy any kind of mains strip that isn't "surge protected and filtered" !) and IF there is noise on the supply the manufacturers should fit the filters in the gear. Of course we now have equipment with amazingly low noise floors so maybe we are fussier!

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Re: Condition of our mains supplies

Postby Hugh Robjohns » Tue Feb 26, 2019 9:20 pm

It is certainly true that even quite modest semipro equipment these days is capable of a much greater dynamic range than equipment of the 70s and 80s, so could arguably be more demanding of power supply noise floors... But then CE requirements demand, and switched mode supplies allow, lower noise floors anyway.

Personally, I don't have any mains noise issues at all, and almost never do, even when working on location. We have overhead power lines feeding the village here, so brownouts are common on windy days, but a big UPS takes care of that for anything critical. But I have no mains-carried noise problems. I'll try and hook a scope up via a transformer when I get a chance to run a spectrum analysis that I can post here...

In my experience, though, most of the alleged mains-carried noise problems are usually attributable to inappropriate mains distribution arrangements leading, inevitably, to ground-loop problems (especially when working with unbalanced outputs from synths etc) and/or just poor-quality equipment design.

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Re: Condition of our mains supplies

Postby blinddrew » Tue Feb 26, 2019 11:43 pm

No noticeable mains noise up here (that i'm aware of), if i bump into the Extinct Audio folks I'll ask them as they have more exacting requirements! :)
Not sure what my folks place is like in Norfolk as I've not done any recording there since my old 4-track days.
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Re: Condition of our mains supplies

Postby Watchmaker » Wed Feb 27, 2019 12:15 am

I used to work for an electric supplier (States) with 16 million customers. I assume by mains power you refer to the line voltage delivered by the distribution system to your meter?

The electric market has basically three steps. Generation, transmission, and distribution. Each has it's own challenges and in the distribution area, complexity increases quickly and steeply as a function of population density.

Generation has benefited from serious technological improvements in many areas, and it in it's simplest form, much of the irregularity people experience occurs in distribution to less developed areas for two reasons. One, there is less infrastructure, so less redundancy which means load balancing is less...balanced. Two, rural infrastructure tends to be left in place for it's entire service life and is generally harder to upkeep.

"dirty " or noisy signal means to me either a widely erratic oscillation around an intended voltage, e.g. anywhere from 210-250V on a 230v line, or it means the line voltage is acting as an unintended carrier wave for some other waveform which is picked up by electronics. Contamination of voltages is extremely unlikely at transmission levels (47Kv and up in the US) and the same is true for most of the distribution network. Stepping down to service voltages is the most likely break point for noise.

There's massive amount of EMF radiation out there but I'm under the impression that that's what rectifiers are for?
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Re: Condition of our mains supplies

Postby Martin Walker » Wed Feb 27, 2019 1:22 am

I've long been interested in this topic, and have regularly heard differences in mid-range hi-fi systems when the local UK mains power supply ends up a little under par here in rural Cornwall.

The most common audio symptom is a lack of deep bass (or rather, when the mains waveform is closer to a sinewave, an increase in low bass). We have a famous slate quarry about 5 miles from us, and I suspect their machinery may be the cause. It's often noticeable on Thursday evening (no idea why) when I notice more effortless deep bass while watching TV.

I also first noticed this in my studio when my power amp transformer starting buzzing, and rigged up a small transformer and resistor divider so I could safely plug the mains waveform into my audio interface for closer examination. My studio doesn't have the change in audio quality that the 'hi-fi' does, so I suspect the quality of my studio gear power supplies is good enough to ride out the mains anomalies.

Here's a typical 'good-sounding' mains waveform here, with only odd harmonic contributions from the slightly squashed peaks (THD is a fairly good 1.25%)

MWmains-13-10-04-2pm-226volt-NOBUZZ.jpg


Now here are a few instances of the mains waveform when my power amp transformer buzzes:

MWmains-13-09-30-2pm-228volt-loudbuzz.jpg


MWmains-13-09-30-4pm-230volt-loudbuzz.jpg


MWmains-13-10-01-2pm-228volt-loudbuzz.jpg


The problems are either noise or even harmonics in the waveform, with the zero crossing area seeming to be most related to the problem.

The last one is what made me think it was due to some large machine somewhere in the area, as the waveform is just so abnormal :headbang:


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Re: Condition of our mains supplies

Postby Watchmaker » Wed Feb 27, 2019 2:19 am

wow, that last one is nuts!
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Re: Condition of our mains supplies

Postby Hugh Robjohns » Wed Feb 27, 2019 10:44 am

blinddrew wrote:... if i bump into the Extinct Audio folks I'll ask them as they have more exacting requirements! :)

In my experience, hi-fi folks seem to suffer more issues with 'dirty mains supplies' because (a) unbalanced connections predominate so EMI and ground-noise is highly likely to get embedded into the audio, and (b) their equipment is often less well engineered, largely due to the loony fashions of high-end hi-fi!

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Re: Condition of our mains supplies

Postby Hugh Robjohns » Wed Feb 27, 2019 10:53 am

Martin Walker wrote:The most common audio symptom is a lack of deep bass (or rather, when the mains waveform is closer to a sinewave, an increase in low bass). ... I also first noticed this in my studio when my power amp transformer starting buzzing

Transformer buzzing is likely to be caused by strong harmonics appearing on the mains supply from -- as you say -- heavy electrical machinery nearby. Although potentially annoying, this shouldn't actually affect the equipment's performance in any significant way.

However, the lack of bass implies the PSU isn't capable of maintaining the DC supply rails correctly when the mains supply gets a bit harmonic-y, which suggests inadequate reservoir capacity on the DC side of the power supply -- so a poor PSU design, basically! That your studio gear copes without issue reinforces my point in the post above!

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Re: Condition of our mains supplies

Postby ef37a » Wed Feb 27, 2019 11:05 am

Hugh Robjohns wrote:
blinddrew wrote:... if i bump into the Extinct Audio folks I'll ask them as they have more exacting requirements! :)

In my experience, hi-fi folks seem to suffer more issues with 'dirty mains supplies' because (a) unbalanced connections predominate so EMI and ground-noise is highly likely to get embedded into the audio, and (b) their equipment is often less well engineered, largely due to the loony fashions of high-end hi-fi!

H

You are too kind Hugh. Most of them could not make an objective judgement if their life depended on it and technically many can't tell their A from their elbow.

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Re: Condition of our mains supplies

Postby blinddrew » Wed Feb 27, 2019 1:56 pm

Hugh Robjohns wrote:
blinddrew wrote:... if i bump into the Extinct Audio folks I'll ask them as they have more exacting requirements! :)

In my experience, hi-fi folks seem to suffer more issues with 'dirty mains supplies' because (a) unbalanced connections predominate so EMI and ground-noise is highly likely to get embedded into the audio, and (b) their equipment is often less well engineered, largely due to the loony fashions of high-end hi-fi!

H
I know Hugh knows this, but for the avoidance of doubt amongst any other readers, I'm talking about this Extinct Audio: https://www.extinctaudio.co.uk/ who are definitely in the sensible side of the market! :D
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Re: Condition of our mains supplies

Postby Hugh Robjohns » Wed Feb 27, 2019 2:10 pm

blinddrew wrote:I know Hugh knows this, but for the avoidance of doubt amongst any other readers, I'm talking about this Extinct Audio: https://www.extinctaudio.co.uk/ who are definitely in the sensible side of the market! :D

Sorry -- yes, don't know why I requoted that bit, really... talking cross-purposes. Didn't mean to imply Extinct (Xaudia) were in the loony hi-fi brigade! :o Heaven forfend! I really shouldn't post before my first morning coffee...

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Re: Condition of our mains supplies

Postby Martin Walker » Thu Feb 28, 2019 4:22 pm

Hugh Robjohns wrote:Transformer buzzing is likely to be caused by strong harmonics appearing on the mains supply from -- as you say -- heavy electrical machinery nearby. Although potentially annoying, this shouldn't actually affect the equipment's performance in any significant way.

However, the lack of bass implies the PSU isn't capable of maintaining the DC supply rails correctly when the mains supply gets a bit harmonic-y, which suggests inadequate reservoir capacity on the DC side of the power supply -- so a poor PSU design, basically! That your studio gear copes without issue reinforces my point in the post above!

That makes perfect sense Hugh - the hi-fi amp in question is a Cambridge Audio Azur 640A - it was modestly priced, yet sounds pretty good the vast majority of the time.

I don't normally notice this lack of bass, but quite regularly I'll say to Belinda "wow - there's a lot of low-end on the TV soundtrack tonight", and it's invariably a Thursday evening.

The only thing I can think of is that decades ago when I was an electronics engineer in a factory, the weekly paid workers got their pay packets on Thursday afternoon, so if this is something that happens elsewhere, I wonder if the machines get switched off on Thursday evening because no-one fancies doing any overtime ;)


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Re: Condition of our mains supplies

Postby Xaudia » Sat Mar 23, 2019 9:34 am

blinddrew wrote:No noticeable mains noise up here (that i'm aware of), if i bump into the Extinct Audio folks I'll ask them as they have more exacting requirements! :)
Not sure what my folks place is like in Norfolk as I've not done any recording there since my old 4-track days.

Hey Drew!

We get the occasional power outage because we're in a rural location about 2 miles from civilisation. No noticeable mains noise problems when using sensible, balanced equipment.

Stewart (Xaudia & Extinct Audio).
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Re: Condition of our mains supplies

Postby blinddrew » Sat Mar 23, 2019 4:32 pm

:thumbup:
We should catch up for a beer at some point soon. :)
(i.e. the next ten years) ;)
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