Hi, newbie question here... there’s a lot of discussion involving the use of Switching Power Supplies or Linear Power Supplies. So I’d like to measure what exactly the difference is between them. But where do I begin? So I want to see with my own eyes purely the difference between what they generate.
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Benchmark Audio links a demonstration video at the bottom of the linked article. As I understand it, all transformers generate RF noise.
Isolating that outside the audio band *should* render a power supply inaudible.
https://benchmarkmedia.com/blogs/ap...audio-myth-switching-power-supplies-are-noisy
Isolating that outside the audio band *should* render a power supply inaudible.
https://benchmarkmedia.com/blogs/ap...audio-myth-switching-power-supplies-are-noisy
solderdude
Grand Contributor
You can built this and have a listen to noise on DC power supplies.
NOT suited for AC power supplies
The Benchmark article makes a big deal about the strength of the magnetic field surrounding the transformer. You will not likely find it easy to come up with a definitive answer as to how important this really is.
As for the DC output of the power supply, the most you'd likely be able to demonstrate or discover is how the filtering needs are different for the two classes. Switching supplies are more efficient, generating less heat within the transformer (probably also within the diodes since diodes are imperfect semiconductors for low voltages in the wrong direction). Aside from the difference in efficiency (and aside from the preference for lower mass), the only way that one class can have an inherent advantage over the other class is if one class does the job at lower cost vs. the other class. It comes down squarely to the difference in what it costs to do the job: what it costs to achieve a DC voltage where the non-DC artifacts are held below some particular threshold that you have chosen, or what it costs to achieve some specific measure of DC stability without using regulation. To show that one class is superior to the other in terms of cost, measurements may have a role to play, but it is not obvious that this would be true.
As for the DC output of the power supply, the most you'd likely be able to demonstrate or discover is how the filtering needs are different for the two classes. Switching supplies are more efficient, generating less heat within the transformer (probably also within the diodes since diodes are imperfect semiconductors for low voltages in the wrong direction). Aside from the difference in efficiency (and aside from the preference for lower mass), the only way that one class can have an inherent advantage over the other class is if one class does the job at lower cost vs. the other class. It comes down squarely to the difference in what it costs to do the job: what it costs to achieve a DC voltage where the non-DC artifacts are held below some particular threshold that you have chosen, or what it costs to achieve some specific measure of DC stability without using regulation. To show that one class is superior to the other in terms of cost, measurements may have a role to play, but it is not obvious that this would be true.
What do you want to measure and what do you expect to see? Most of the negativity about switch-mode power supplies (SMPS) revolves around their high switching frequency. That is a plus, not a minus, as it moves the power supply noise way, way above the audio band instead of at 50/60 and 100/120 Hz with harmonics right in the bass region. The other two arguments against them that I seem to see most often are potential for noise injection and reliability. The former is as true for SMPS as for any other noise source, like an AM radio station, dimmer switches in the house, your fridge and HVAC, and so forth. Well-designed SMPS do not radiate much. They have also gotten more reliable over the years though the high switching rate does make them more sensitive to the output filter capacitors. I have wall warts that failed in a few months, and components that have lasted for 10+ years and are still running. That is true for linear and switching supplies. A lot has been learned in the past couple of decades about SMPS' failure mechanisms and what it takes to make them last.
If you measure at the output of the device being powered, you may not see any difference at all between a linear or SMPS supply.
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I know why. It is a common Audiophool canard that SMPS's are noisy, interfere with SQ, and that only an LPS gives you that clear, jitter-free sound.
Whether the OP heard this on Audiophool Stool or some other site, or from an ignorant dealer is the question.
And how would most people know?
In fact, SMPS are often used for hospital approved equipment, not to mention laboratory use. Of course, you can make a bad one too.
Whether the OP heard this on Audiophool Stool or some other site, or from an ignorant dealer is the question.
And how would most people know?
In fact, SMPS are often used for hospital approved equipment, not to mention laboratory use. Of course, you can make a bad one too.
With something to measure, and something to take the measurements, and some idea what you are measuring and what the measurements might mean in the specific case at hand.
The physical difference between them can be gleaned from a schematic of each. You'd need to know what the symbols mean, and the implications of their use in the specific circuit.
Voltmeter reads voltage - AC or DC - but doesn't provide much insight into quick fluctuations
Oscilloscope provides a visual representation and will show fast moving artifacts - newer devices can add measurements
An Analyzer (captures voltage data over time and looks at fluctuations with software) can provide more details.
What is it you want to know?
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