Switch mode versus traditional power supplies

Paul helps us understand how these new power supplies work and how they differ from conventional supplies.

[MichaelLivingston-me]

Well done, Paul. That's not an easy topic to discuss and keep it from becoming highly technical. Excellent explanation.

[wilcalint]

A commendable job by Paul on this video. One thing that Paul briefly mentioned that I wanted to expand on. "Switching" Power Supplies have oscillators in them. And those oscillators are certainly over 10Khz. Paul said that Switching power supplies create "noise" and that is very true. And because of that, per the FCC ( Federal Communications Commission ), requires any consumer device with an oscillator over 10Khz MUST carry a testing for compliance certification number. Purchasing an off the shelf power supply that is already certified does not absolve you from getting your entire product retested and certified. All of that can be a pain in the ass. Been there, done that.

[mariofilippi]

After years of trying to understand the difference, your explanation of linear vs. switching power supplies was the most well thought out explanation. Thank you.

[RogierYou]

Toroidal transformers are heavy and make your equipment feel more expensive 🤣

[TPQ]

Paul, thanks. Many others have tried to explain this, took longer, used graphs and acronyms, and left me perplexed.

[ivoverhoef]

Great ‘simple’ explanation Paul. Thanks!

[tkjho]

I have a Technics mini-system that has a separate Pulse Power Supply Unit SH-C01 for the 50W RMS amp SE-C01. It was bought in 1979 and looks like it was 45 years ahead of its time.

[ThinkingBetter]

For a power amp, traditional transformers are not regulated and the voltage drops by the signal load and mains power fluctuations. Capacitors are used to help on that.
A switch mode power supply can provide precise regulated voltage and also eliminate the need for an external power regenerator as it sort of does the same.

[ScottsLifeOffGrid]

Paul, I really appreciate your videos, Thanks!

[L.Scott_Music]

You explained it well and it was less than two minutes more than the average video.

[dsched]

Switching power supplies are nothing new. Science discovered long long time ago that as the frequency went up, the size of the transformer went down to transfer the same amount of power. So, if you wanted a smaller power supply, you would take the incoming 50 or 60 Hz power, put it to an oscillator that would "switch" it at a much higher frequency, then use a much smaller transformer to make a conventional (linear) power supply. But now, you would also need some extra filters to clean up the higher frequency components brought on by the oscillator. That's what it is in a nutshell...

In most cases, switching power supplies are chosen to eliminate an large, expensive transformer. Therefore, most switching supplies have the number one design goal to be "cheap" and, in line with this goal, the filtering I mentioned above is also not done properly. The lack of proper filtering and shielding makes most commercially available switching power supplies a poor choice for high end audio.

Of course, a switching power supply can be designed and constructed in a (expensive) way to have an excellent noise filtering, which would make it suitable for high end audio use. However, almost nobody does that because you don't want to deal with such a complex design when you will likely have no cost or performance advantage over an equivalent conventional (linear) power supply.

[stephensr]

They are improving but they are still chosen purely due to cost savings. Sometimes up to 25% of the retail price. Most have the switching PS outside the box on the power cable to reduce radiated noise, case size and weight. Just like with all laptops. One of the leaders in this field are Lumin Audio owned by Pixel Magic. Their built in switching PS have lots of shielding. However their higher end models still use toroid or offer one as an upgrade. They just sound better.

[gtrguyinaz]

Spectron first developed a switch mode power amp and it was very good in 1999…
I owned 1 and it was great… combined with my audible illusions pre amp, it was as good as anything …

[maynellrodrigues]

I'll take the robustness of the transformer instead of a sensitive SMPS ✨

[chebrubin]

SMPS in an Emotiva Reference Differential sounds amazing.

[rugerthedog]

Good overview! However, Paul didn’t discuss all of the detail of the noise problems with switch-mode supplies. Noise problems occurs not only at the switch frequency and it’s harmonics, but also sneakily via ringing on the switch transition. Ringing can have a fundamental and harmonics from 10’s of MHz to beyond 100MHz. Ringing noise is particularly more prominent where the switching transistors are external to the controller. Both types of noise can travel not just via radiation, but conductively onto the power supply output voltage, and also back onto the power line. Part of the art Paul refers to is understanding the pitfalls and techniques of making the power supplies “good citizens” that don’t put out wide-band noise interference into the product itself and into the user’s environment.

[tpock]

Better or cheaper 🤔 The bean counters always win

[samirpradhan]

Looks like, we all have missed one very important aspect with respect to bass production. It is normally believed that SMPS in hi-fi audio can't handle transient bass response like linear PS does. That may be one of the reasons why audiophiles do not like SMPS.

[jimeadie]

The difference is a switched mode power supply uses an inductor rather than a transformer.

With a switching frequency of 100KHz rather than 120 Hz for full wave rectification they switching power supplies don’t need as much filtering to remove audio frequency noise.

Somewhat like a comparison of a conventional water heater vs tankless. Old approach vs higher efficiency.

[KenTeel]

If I remember right, a switch mode supply uses a transistor that turns fully on and fully off very fast. This is called switching a transistor between saturation (fully on), and cut off (fully off.) The out put of the transistor is hooked to the primary windings of a transformer. The secondary winding (which is and isolated winding from the primary windings) has more windings than the primary windings. Therefore it's a stepup transformer. This output voltage, from the secondary windings, is fed into a capacitor (or several capacitors.) As the transistor switches on and off, alternately, the secondary windings charge up the capacitor. This capacitor is the "resovoir" of current and voltage that powers the amplifier section of an amp. Now, I'm going by memory on this description, so, if anyone sees flaws in this general description, chime in and correct what I've posted here. In my description I used a single transistor. In reality there can be more than one switching transistor.