How a power supply works

[andyjm]

Given the apparent popularity of my explanation of why a star connected mains strip can't possibly make any difference to sound quality, I thought I would extend my occasional series to Power Supplies. Given the breadth of the subject, this may have to be a multi part posting.

Linear audio amplifiers of the type found in home hifi need a stable and clean DC supply to operate. The problem is that most amplifiers are mains powered, and mains is AC. Mains is too high a voltage to be useful for home hifi, and also has the real possibility of killing you.

So, in no particular order, a power supply has to:

1. Isolate the equipment from the mains

2. Drop the mains voltage to a suitable level

3. Turn the AC into stable DC

4. Filter out any noise

As any follower of Nikola Tesla will know, he was the proponent of the 'multi phase AC system' which was in competition with Edison's DC system - the so called war of the currents. For various technical reasons, home mains AC supply isn't multi phase, it is single phase. For those who can remember their physics, a single phase mains waveform displayed on a 'scope looks just like a simple sine wave (because it is).

Now this is where the first 'inconvenient truth' shows up for the mains cable brigade. That mains sinewave crosses through zero twice every mains cycle. At that point, there is no power at all coming down the mains wire - if you were quick enough with a voltmeter, and could connect and disconnect it just at the zero crossing point, it would measure ZERO volts.

Hmmn. So twice every mains cycle (100 times per second), there is a period of time where NO power comes down the mains lead at all. What if (Sir) RIngo Starr was bashing his cymbal at just the point the mains crossed zero - would there be silence out of the speaker? Experience would indicate that you can still hear the cymbal, so either (Sir) Ringo has excellent timing and misses the zero crossing point, or there is something else going on.

I will explain in the next post what is going on, but the first question for the cable brigade is if there are significant periods of time when the cable is not conducting at all, how can it possibly effect transient response during the period there is no power coming down the cable?

 

[chebby]

There you go, blinding us with facts again!

(Actually keep it going, I left all this stuff behind after my A’Levels 37 years ago, so i’m happy to have a refresher.)

 

[nick8858]

A nice clear summary. Thanks for that. Makes you wonder why one would need a mains conditioner if one of the first things your amp does is convert it to DC? Maybe an incoming "dirty" AC supply without conditioning results in an equally "dirty" DC supply after conversion? Maybe the conditioner makes sure the AC is always going in the same direction? Like those speaker cables with arrows on them....

 

[Samd]

There you go, blinding us with facts again!

(Actually keep it going, I left all this stuff behind after my A’Levels 37 years ago, so i’m happy to have a refresher.)

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

 

[CnoEvil]

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

Fair enough....as long as it also works the other way round.

 

[QuestForThe13thNote]

Just as a suggestion why don’t you write up your review that mains blocks, mains cables don’t make a difference, in your view, and your reasons why so. Then go to various cable companies and send them an email of this view, and come back with what they say, perhaps after a discussion. Then present both and let us make our minds up. Maybe you could even extend investigations of what they tell you further.

That way it’s a lot more balanced a view leaving people to decide. If you simply say this cannot make a difference for x reason, and coming up with technical explanation why, then the article is little more than your view, and it’s a bit like you just telling us what to think. I’m sure that would be very much more informative and scientific. The reasons that these cables do work, as is known by many of us, could be a reason you don’t know of or with respect to you, you simply have not considered.

the first one you could do power bars, and mains cables. Your hypothesis could be ‘do star wired and mains cables make a difference to bubar blocks with spike protection, and standard kettle leads’. I’d be very interested in you doing that.

 

[jimmy1]

I dont care if they work or not, my only point is decent quality copper cables should not be costing hundreds of pounds, they must only cost pennies to make its a crazy mark-up

 

[jimmy1]

Probably easier to sort out the isreal - palestine situation mate, going by any cable debate thats ever taken place

 

[nick8858]

Wondered how long it would before this poster appeared. Interested in no one else's opinion but his own. Arrogant, argumentative and frankly downright disrespectful. Please remove him from this thread.

 

[Andrewjvt]

But on your question...... if it’s 100 times per second and you are right, the point I think you are trying to get at i think, is that in these periods of no signal when we should be hearing Ringos Cymbal, the capacitors in the high Fi are taking care of sound duties, and thus by inference the sound is coming from the hi Fi and not the cable, if you understand me. But the cable is still in a circuit with the hi Fi one though.

but to extend that thinking with my layman’s knowledge I’d ask what time scales are between the on and off nature of the sine wave. Is it such that it can be amalgamated together as one sound, how much effect do the capacitors in discharging current have on this, how much do they discharge. These are surely all things which can or could have a bearing (not that I’m saying they will) but I’m trying to put the point across to others on this forum that the kind of black and white thinking but not joining things up, is extremely easy, but working out what is going on, is by virtue of asking these types of questions, and thinking about it more, very hard. 

Don't worry about multiple posts of confusing reasoning.
The science of power supplies does not apply to your equipment as your amps are over the £8000 price point formula where all science and laws of the universe don't apply

Now for me it's an entirely different matter as I'm far off your league of equipment so I'm more interested in the correct facts.

 

[QuestForThe13thNote]

But on your question...... if it’s 100 times per second and you are right, the point I think you are trying to get at i think, is that in these periods of no signal when we should be hearing Ringos Cymbal, the capacitors in the high Fi are taking care of sound duties, and thus by inference the sound is coming from the hi Fi and not the cable, if you understand me. So I think by this thinking, you reach a view the cable isn’t involved at all? But the cable is still in a circuit with the hi Fi one though. Also the whole debate of effects of rfi on cables and frequency response is another debate.

but to extend that thinking with my layman’s knowledge I’d ask what time scales are between the on and off nature of the sine wave. Is it such that it can be amalgamated together as one sound such it wouldn’t matter in any event ie ears filling in the difference, how much effect do the capacitors in discharging current have on this, how much do they discharge, how fast are they relative to your point I think in para a. These are surely all things which can or could have a bearing (not that I’m saying they will) but I’m trying to put the point across to others on this forum that the kind of black and white thinking but not joining things up, is extremely easy, but working out what is going on, is by virtue of asking these types of questions, and thinking about it more, very hard.

I think judging by the fact you didn’t want to answer to some of the points on the other thread, you probably aren’t interested in getting to these types of question, that you just want to push a view. If you do, not much point debating, but if the opposite, I’m al for it.

 

[QuestForThe13thNote]

I’m very interested in hearing it from both sides - that’s why I said I’d like him to do it with balance. The second one from andrewjvt is just schoolboy retort stuff.

 

[Andrewjvt]

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

Fair enough....as long as it also works the other way round.

Cno
We often disagree over such things but strangely we never fall out or hold a grudge.
We also agree on things from time to time.
I think the reason is we don't think our hifi is a willy measuring stick.

 

[QuestForThe13thNote]

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

Fair enough....as long as it also works the other way round.

Cno We often disagree over such things but strangely we never fall out or hold a grudge. We also agree on things from time to time. I think the reason is we don't think our hifi is a willy measuring stick.

I’d like this back on the topic. If it’s not going to be sensible then I don’t think people will bother, at least the ones who want to explore this issue.

 

[nick8858]

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

Fair enough....as long as it also works the other way round.

Cno We often disagree over such things but strangely we never fall out or hold a grudge. We also agree on things from time to time. I think the reason is we don't think our hifi is a willy measuring stick.

I’d like this back on the topic. If it’s not going to be sensible then I don’t think people will bother, at least the ones who want to explore this issue.

It will be sensible if you would kindly refrain from rambling diatribes, and acceptance that others have a point of view as valid as yours.

 

[ellisdj]

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

Fair enough....as long as it also works the other way round.

Thats is pot and kettle for sure I was asking for that years ago I felt it would be much better

 

[QuestForThe13thNote]

Yes I do accept that mate. But a point of view like mine, can be explored and it’s open to criticism.. This doesn’t necessarily mean it’s personal critisism, which seems to come across in what you think I’m doing, in somewhat aggressive nature of your posts here.

 

[BigH]

Cables manufacturers will probably come back with some vague statement saying our buyers are happy and think they make a difference. Otherwise they may get fined for making claims they can't prove, like Naim did a few years ago.

 

[QuestForThe13thNote]

There would be plenty of people who write blogs and have a strong background in electrical engineering who have a view the power cables do make a difference, who andyjm could go to.

 

[nick8858]

And plenty of people who can advise completely the opposite point of view presumably...but you wouldn't be interested in that

 

[BigH]

There you go, blinding us with facts again!

(Actually keep it going, I left all this stuff behind after my A’Levels 37 years ago, so i’m happy to have a refresher.)

It would be nice if the moderators(?) kept this to fact comments only and let the Which (cable) Doctors have their own thread.

What moderators? only seen them once in the last 6 months, when someone had to take a long holiday.

 

[QuestForThe13thNote]

Of course I am interested. That’s why I’m debating. There are going to be bits of thevopposire view I will have to accept that don’t help to explain why power cables make a difference, and alternatively your side will have to accept concessions. I’m just interested in what’s probably going on to hear differences. Can I suggest please you stop doing this, it doesn’t add to the thread

 

[CnoEvil]

Cno We often disagree over such things but strangely we never fall out or hold a grudge. We also agree on things from time to time. I think the reason is we don't think our hifi is a willy measuring stick.

Exactly....and why I don't list my kit, boast about it, run down others' kit...or indeed insult anyone who holds a fundementally different view to mine.

Live and let Live is a good way to approach a forum. If people want to hear what I have to say, that's fine...and if they think I'm an idiot, then that doesn't worry me. I have posted enough on here, for people to make a judgement...and am happy to be judged by that.

 

[cheeseboy]

I’m just interested in what’s probably going on to hear differences.

well you could start by trying to rule out biases and placebo before you start on the nitty gritty. I know you seem to hold the view that you are immune, but you are not, nobody is. These things have been scientifically proven again and again without fail. So, if you want to approach it scientifically as you keep claiming you do, start with the science that's already out there and had been proven. No doubt you'll now just dismiss it all out of hand without acutally presenting any scientific proof whatsoever as you usually do and then ramble off in to one of your narcissistic incoherent rants to back up what you say in your in own head.

 

[ellisdj]

Cheeseboy - noone thinks their immune to anything, thats never what its about but what would do you do as an individual - all the best sound you have ever heard - from a huge variety of listening has been with systems with good cables and mains products in them - the best sound I have ever heard had the best mains products in the system - thats the truth, I am not the only person who thought that about the sound of that system.

By compare the systems you have heard that havent sounded any where near as great havent used the cables and mains products mentioned or hasnt used them to the same level.

Then you think whatever influences are at play here - this way sounds best so why I would I look to do it any other way - when this way sounds best?

Thats whats important here fundamentally - creating that great sound