Don't let anyone tell you mains supply doesn't matter

[Alexh]

It would be worth reading "Recording Studio Design" by Phillip Newall who knows what he is talking about when it comes time to put in the mains supply.
Many "engineers" do not understand the need for large low impedance cables for the monitoring system.
I followed the advice and it does actually work.

 

[Mike Reed]

Many "engineers" do not understand the need for large low impedance cables

For the mains supply (to kit) or speaker cables?

 

[Alexh]

For the mains supply (to kit) or speaker cables?

The mains supply and yes the speaker cables as well

 

[Mike Reed]

The mains supply and yes the speaker cables as well

With my very non technical logic I've always assumed that the larger the conduit, the less impedance is incurred. Hence my and others' 10mm2 t & e radials for hifi. Naim's NAC A5 cable receives a lot of abuse but has relatively thick stranded cores. Mine not only accompanied upper Naim and big m/coil speakers, but still does a sterling job with valved kit and big ESLs, whereas Chord Odyssey (thinner) failed miserably when I changed horses.

 

[mansr]

With my very non technical logic I've always assumed that the larger the conduit, the less impedance is incurred.

That is true, but beyond some point, bigger/lower stops being better. For power wiring, what matters is that the voltage at the input to the equipment remains within the design spec. With too thin a cable, the voltage might drop below the minimum required for correct operation, which is probably what happened to the OP. Equipment must be designed to work correctly over the full permitted grid voltage range, and since the actual voltage is usually well above the minimum, there is rarely a problem. Of course, a thin power cable can become dangerously hot under high load, but that doesn't affect the performance of the connected equipment (until the house burns down).

Speaker cables are subject to a totally different set of considerations. Here the most important thing is that the resistance (plus the output impedance of the amp) is much smaller than the minimum impedance of the speakers. If not, frequency response can be affected, among other things.

 

[electrogizmos]

I could give you my opignon about power supply with my naim cd 3.5 cd player,I made a flatcap clone that will take care of the audio part and the result were fantastic,more details etc

 

[Martyn Miles]

The mains supply does matter.
My audio system won’t work without one.

 

[wow&flutter]

Surely if the rectification in the equipments power supply is properly designed any noise and voltage fluctuations should be filtered out?
The pre amp or power amp stage in your amplifier is not relying on a perfect 240v @ 50hz is it? Internally the equipment is running on a much lower dc voltage.


Dives for cover!

 

[M4RK5]

The original cable buried in the road would have been specified for a much lower load than it would have experiencing when it failed. Pulling excess current through a cable generates heat which increases the resistance off the cable resulting in increased voltage drop and possible eventual failure of the cable through overheating. The generation set would have been producing a clean 240v sinewave unaffected by current draw from the rest of the street on the same phase as you.

Spot on description of the likely failure mode, and you are right a gen set will produce cleaner mains, there is a huge amount of noise on mains electricity, a lot of industry use drives these days for various processes and these feed a lot of noise back on to the grid, if you ever have a mains analyser set up in your home you will rarely see a nice sine wave and there can be a significant amount of harmonic artifacts superimposed into the mains, you can also get significant, albeit fleeting voltage spikes.
As for the electricity company electrical engineers, they have very highly trained and experienced power system engineers that are extremely knowledgeable regarding power systems and power quality.

 

[mansr]

if you ever have a mains analyser set up in your home you will rarely see a nice sine wave and there can be a significant amount of harmonic artifacts superimposed into the mains

See previous page for an example.

you can also get significant, albeit fleeting voltage spikes.

I'll have to check for that.

As for the electricity company electrical engineers, they have very highly trained and experienced power system engineers that are extremely knowledgeable regarding power systems and power quality.

Of course they do. Those are not necessarily the ones doing the actual work connecting up cables out in the streets, though. That job requires a different skill set. Besides, none of them are likely to be knowledgeable about amp design.

 

[M4RK5]

See previous page for an example.


I'll have to check for that.


Of course they do. Those are not necessarily the ones doing the actual work connecting up cables out in the streets, though. That job requires a different skill set. Besides, none of them are likely to be knowledgeable about amp design.

I have to disagree, one of the engineers I worked with had not one but 4 doctorates, one of which was electronic design, and guess what his favourite hobby was.....yes the same as ours, he used to design and build his own audio gear.

I had a look at your sine wave, it is remarkablely clean apart from slight clipping, it's not what I would usually see in the UK, and its at 690VAC, UK mains voltage is 230VAC approx, derived from 400VAC three phase street voltage.

 

[mansr]

I have to disagree, one of the engineers I worked with had not one but 4 doctorates, one of which was electronic design, and guess what his favourite hobby was.....yes the same as ours, he used to design and build his own audio gear.

So you know one who shares our interests. Of course there are a few of them. And this guy, did he work on cables out in the field? That level of education is definitely not typical for someone doing that job. Most of the people I know (and know of) in that line of work don't have so much as a college degree. It is simply not required.

I had a look at your sine wave, it is remarkablely clean apart from slight clipping, it's not what I would usually see in the UK, and its at 690VAC, UK mains voltage is 230VAC approx, derived from 400VAC three phase street voltage.

Huh, it's a little under 250 Vrms, typical at my house. I got the graph using a Keithley DMM6500 which I think ought to be up to the task.

 

[M4RK5]

So you know one who shares our interests. Of course there are a few of them. And this guy, did he work on cables out in the field? That level of education is definitely not typical for someone doing that job. Most of the people I know (and know of) in that line of work don't have so much as a college degree. It is simply not required.


Huh, it's a little under 250 Vrms, typical at my house. I got the graph using a Keithley DMM6500 which I think ought to be up to the task.

Hi, you're right the guy in question wasn't the norm, but he'd be onsite regularly.

It looks like 690v p-p to me. The Keithly is a very good bit of kit. We used a Fluke Norma 5000 (older version tbh) it can see transient voltage spikes on the waveforms (which can be numerous and surprisingly large in amplitude) and can be used to examine the harmonics present, I don't think your Keithly has the same resolution which is likely why the waveform is so clean.

 

[mansr]

It looks like 690v p-p to me.

Yes, and if that were a perfect sine, it would be 244 Vrms.

The Keithly is a very good bit of kit. We used a Fluke Norma 5000 (older version tbh) it can see transient voltage spikes on the waveforms (which can be numerous and surprisingly large in amplitude) and can be used to examine the harmonics present, I don't think your Keithly has the same resolution which is likely why the waveform is so clean.

It can sample at 1 MHz in 16-bit resolution. I think that should be good enough to catch anything that's likely to come down the power line. Of course, a rare event is unlikely to be captured without setting up a trigger to look for it, which I hadn't done.

 

[M4RK5]

Yes, and if that were a perfect sine, it would be 244 Vrms.


It can sample at 1 MHz in 16-bit resolution. I think that should be good enough to catch anything that's likely to come down the power line. Of course, a rare event is unlikely to be captured without setting up a trigger to look for it, which I hadn't done.

I don't think the Keithly is capable of capturing harmonic content, the fluke is designed to capture harmonics as it used to analyse power quality, not just carry out measurements.

 

[mansr]

I don't think the Keithly is capable of capturing harmonic content, the fluke is designed to capture harmonics as it used to analyse power quality, not just carry out measurements.

It doesn't have a built-in FFT function, but it's easy to export the measurement data and perform any desired analysis in software. Here's the spectrum up to 1 kHz:

 

[M4RK5]

It doesn't have a built-in FFT function, but it's easy to export the measurement data and perform any desired analysis in software. Here's the spectrum up to 1 kHz:

The main difference is the FFT function and the price (the fluke ain't cheap), but if you're able to perform the analysis in another tool you can't fault that, you might want to input your waveform capture and do the same, you might be surprised by the amount of noise present.

 

[mansr]

The main difference is the FFT function and the price (the fluke ain't cheap), but if you're able to perform the analysis in another tool you can't fault that, you might want to input your waveform capture and do the same, you might be surprised by the amount of noise present.

That spectrum is from a capture of the power line voltage. Here's a wider frequency range:

Those spikes around 21 kHz and 33 kHz could be SMPS noise. There's about a dozen of them connected nearby.

 

[Colonel_Mad]

The hi fi has, unsurprisingly, sounded flat and dulled since the outage.

Today I have depth and sparkle back!

So you mean it was good before and good now but whilst you were on the generator it was dulled?

We had a similar thing last year but only the cable that ran from the road to our front door fried. The whole area had a power cut but when it came back on we were the only people who remained in the dark. A massive generator and workmen digging through the night for 4 days didn't endear us to the neightbours! I did listen out for changes in the hifi SQ but couldn't hear anything in our case.

Having said that my turntable had a small but audible/annoying wow, on sustained piano notes in particular. I got a Heed Orbit 2 for peanuts that regulated the power to the turntable rather than relying on stable mains and it solved the problem in an instant.

 

[kjb]

So you mean it was good before and good now but whilst you were on the generator it was dulled?

We had a similar thing last year but only the cable that ran from the road to our front door fried. The whole area had a power cut but when it came back on we were the only people who remained in the dark. A massive generator and workmen digging through the night for 4 days didn't endear us to the neightbours! I did listen out for changes in the hifi SQ but couldn't hear anything in our case.

Having said that my turntable had a small but audible/annoying wow, on sustained piano notes in particular. I got a Heed Orbit 2 for peanuts that regulated the power to the turntable rather than relying on stable mains and it solved the problem in an instant.

Pretty much - after the outage the sound stage became two dimensional and the music lacked dynamics and rhythm. It was good and i my impression is that it is even better now - I'm having to turn the volume up less to drive the speakers, the sound is more "in the room" than before and I can definitely hear more detail like the finger work on a double bass that simply wasn't as noticeable before. To my ears the sound is now better than it was pre-outage.

I have a 15w valve based integrated amp - I don't know if these are more susceptible to changes in power than solid state amps .

I put up the post as I was interested to see what the engineering / scientific explanation for this. As a right brained non engineer I'm trying to untangle the responses.

It seems:

1) I may have had "better" or cleaner source from the generator - although from a users perspective it was less consistent during this time - lights dimmed throughout the house when high usage devices like the oven or shower were switched on and , musically, the hi fi sounded flat and under-powered
or
2) The new mains cable might be delivering more consistent power leading to an improvement
or
3) I imagined it all and am an idiot

or any combination of the above.

( Note: Mrs KJB, who occasionally thinks I'm an idiot, thinks the difference in clarity and dynamics is very noticeable)

The outage was on the 1st March. Today they are filling in the final trenches in the road. The blowout has had quite an impact.