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Komputers and Power Supplies

Posted by Thorsten (M) on September 22, 2014 at 09:36:24

In Reply to: RE: Windows or Apple for 2014/15? posted by Thorsten on September 19, 2014 at 23:41:11:

Folks,

What a kerfuffle. Really not needed. It's only audio...

I'll not have the time to address individual points raised, I'll try something more general.

Let me first be clear, Audio (including via Computers) is a basic technology, which on a macro level is understood fairly well. As always the devil is in the details, but there is no need for religion and/or for supra-natural things (in most cases anyway, sometimes exorcisms and holy waters may be needed).

It also means that Audio is generally amenable to using the scientific method (in a way it is not in answering "Ultimate" Questions). That means we need to work evidence based.

Now this does not mean that we, at the slightest notion of anything no covered by EE101, jump up and demand to bring in Arny "Audio Whytchfinder General" Krüger.

And for the "Whytchfinder General" to administer a ABX type Blind Test, if necessary by force and should the poor Whytch or Warlock fail the pre-rigged ABX test just burn her/him on the stake or at least ridicule them publicly for all it's worth.

But it does means we look closely and avoid linking observation (If I do A I get B) to a rigid (but usually misleading) theory of "I only can get B if I do A". Indeed, if we actually looked carefully and with understanding we may find that while 1A may give us a 1B result, applying 1C may indeed give us a 100B result.

The key is to really understand how much of what (A, C, D, X) can produce the most "B" with the least inconvenience, cost, weight etc.

My comments were meant in this context.

We must understand first what is going on.

Otherwise we get people blaming "long and stiff cables" for making "excellent emitters" (a freudian slip perhaps revealing N'V of the supposed attributes of the Son's of Ham?), when there is (or should be at any extent) an absence of much of anything to emit (excluding nocturnal emission while having dreams of Son's of Ham with long and stiff... ahhmmm ... cables).

And when given whatever electrical frequency might be available to emit, the cable length is actually woefully short to much of any emitter, never mind that all cables parallel ground and power meaning they make some of the worse possible emitters, if you tried to make a device that emits RF.

Back to the topic though, as much fun as dilettante style psychoanalysis is.

With a computer and a power supply (linear or not) we have three things to concern ourselves with, in terms of where we may do damage.

1) Noise kicked back or conducted back into the mains (and from there into a connected audio system) - this mains may be generated by many sources or indeed noise originating in the Computer itself that is conducted into the mains.

For such noise most linear supplies I have seen advertised offer poor performance. Here using a suitable mains filter will do a job 100 or even 1,000 times better than a linear supply for a fraction of the cost (see above 1C = 100B where 1A = 1B). Of course, perhaps such a filter SHOULD be build into such power supplies. Blame (as usual) the bean-counters.

2) Noise generated within the supply itself and not sufficiently eliminated at the point where the power leaves the supply that can impact on the power-supply in the computer.

For such noise both kinds of supplies can be anything from awful to excellent. It is an engineering challenge but not one that is particularly difficult for either linear or switched mode supplies. Again, beancounters can wreak havoc.

That said, given that computer motherboards tend to include massive amounts of additional power management (read switched regulators, LC filters, local decoupling with usually quite big value cap's) as do most add in cards, the real impact of such noise on the functioning of a computer is questionable, though cannot be completely excluded.

What is more, as long as data is not corrupted (and you will know if it is) and as long as an externally powered asynchronous DAC is used which eliminates source (Computer caused) jitter, it matters, as the Irish say so charmingly "Feck all". This externally powered asynchronous DAC (implying BITPERFECT ASYNCHRONOUS - no ASRC please) does not have to be per se ASYNC USB, though that is easiest and most widely implemented, other schemes are possible.

3) Noise from either mains and/or the power supply itself that is allowed to pass the power supply and is conducted by the PC to DAC/System connection into the audio system.

Such noise can be pernicious and hard to control.

The easiest way is to take a republican (as in the spanish civil war) "No pasarán!" stance (for those who prefer LOTR - Gandalf: "You — shall not — pass!") and simply isolate the PC side from the audio side in ways that make passing such noise either impossible, or at least dramatically reduces the transmission.

Doing so may impose unacceptable limitations.

Then mitigation becomes the second option. Mitigation can be substantial too, but few things beats just simply destroying all bridges the noise may use to escape from the deeps of Moria, oops, from the case of the PC. Ask that demon from LOTR if you want an honest opinion.

So my take remains - block noise from the PC and associated "potentially noisy/dirty" components from getting to anywhere where it could do damage and/or is not wanted (mains, audio system) and make sure the PC has no control over your audio clocks other than stating what sample it would like (via an isolated link).

And quite frankly, I can think of little that would less suited to that kind of job than a linear power supply. And I can think of a lot fairly affordable Gizmo's that address the problem well.

Enough for today.

Hey Lassi, bring us another one of Dublin's finest... Pure Genius.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

This post is made possible by the generous support of people like you and our sponsors:

Atma-Sphere Music Systems, Inc.

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