What is a linear power supply and what is it used for/advantages?

Sorry for the seemingly silly question - I just do not understand the purpose of such linear supplies nor know whether they can be used with any audio equipment (bearing in mind that most if not all of them already have PSUs built-in).

Lastly: can someone provide links to the most recommended/common linear supplies so I know what they are/look like?

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Depending on how old you are, of course, a linear power supply is popularly speaking the old fashioned transformer + rectifier way of regulating voltage, as opposed to the modern switch-mode power supply which rapidly switches between states to do the same. The practical difference is that a linear power supply converts power to heat where a switch-mode PSU doesn’t (much). A linear power supply tends to carry mains noise; a switch-mode creates its own noise, albeit at much higher frequencies - debatably easier to filter.

The only reasonably comprehensible explanation of switch-mode I can think of, is this…

Switched-mode power supply - Wikipedia

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So unless I am stupid, every reason you put above tends to support the use of normal PSUs, NOT linear…so why do people want to use them? Or have I missed something?

This test might be of interest for you: Multitest external 12-volt power supplies - Alpha Audio NET

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I honestly can’t say. I have never heard a really good argument to their advantage in hifi. I could speculate that some might pick them for the positive ring to linear, but I won’t :slight_smile: and seriously doubt it. Let us see if someone chips in with a good explanation…

Ok, noted - so this is probably as “necessary” for hi-fi as audiophile switches and esoteric power cables… :smiley:

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If a device can take an external power supply then they can make a difference. Using an RPi with a better supply than the ÂŁ8 stock one is worthwhile for example.

Don’t get too hung up about the type of power supply though. True a lot of the better ones are linear. But switched mode ones can work well too. dCS use a mixture of linear and switched mode in some of their kit for example, and for sure they’re not going to use anything substandard. At a price more relevant to most of us Allo’s Nirvana is switched mode.

Was the question a generic one or do you have a specific device in mind? I’d certainly put power supplies way ahead of power cables or ethernet switches in importance / impact on SQ.

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A liner supply has a much lower noise floor then a switch supply. So it sends less noise to the device it’s connected to. It’s an AC to DC supply so you can only use one if your device has a DC input.

I recommend Linear supplies (LPS) for our Rendu (Ethernet to USB) players.

My customers have also heard improvements in sound by using them to replace the switching supplies that came with their DAC.

This is a link to a good one from our web site.

You will notice they are quite a bit bigger then the supplies they replace. This is because they need a large copper transformer to reduce the AC voltage coming in to a voltage that the linear regulator can use.

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Phil, do you have measurements that confirm that? I’d love to see them. Also, what are the parameters of “worthwhile”, if you can share that? How much worth for how much while?

While keeping an open mind on this topic, I tend to think that linear power supplies are another audio shibboleth, a holdover from earlier decades of audio, especially the 1980’s, when switching power supplies were newer and noisier. For computers, like the Pi 4, I see no point to them. For analog gear, like tube amps, particularly ones with poorly built power conditioning circuits, they might or might not change the sound of the equipment, I’d think.

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Bill

Hi, happy Friday :slight_smile:

I don’t have comparative measurements but if we take the iFi £50 supply as a benchmark (it’s what I was thinking of for the RPi) then iFi provide some info on their website here. Likewise Allo on their equivalent, the Nirvana, here.

I’ve also listened to the difference the iFi makes to an RPi; in my view it’s well worth the cost.

Interestingly when my son was looking for a new DAC we tried an RPi with Allo Boss HAT against an Audioquest Red. With stock power supply he preferred the Dragonfly. With the iFi power supply the improvement was obvious (to him and me). He ended up buying it (or rather muggins dad did here for his Xmas present). The key point is that he’s a relative newbie in audio, yet he could clearly heard the difference (through a crappy amp and speakers too). If you’re interested his next purchase was IsoAcoustics Pucks for his speakers - again he heard a clear difference with and without them.

I know you’re a measurements guy, I suspect I haven’t convinced you. If so fine. I would encourage people to try better power supplies though. Whether internal or external, power supply circuitry is a big focus for most electronics designers as lower noise equals better sound. And noise is measureable.

Cheers, Phil

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The iFi Power appears to be switch mode with some fancy “audiophile” filtering. If YOU hear a difference nice, but don’t confuse it with a linear PSU, unless I’m looking at the wrong one?

The Allo Nirvana is SMPS as well. Although I haven’t heard that.

As I said the technology per se is less important than how it’s implemented. A poor linear supply will sound worse than a good SMPS one. The dCS example came from when I visited them. They said they used whichever was better for the job, linear wasn’t inherently better than switched mode and vice versa.

And yes I heard a difference between stock power supply and the iFi one with an RPi (3 to be precise). The stock one sounded harsher, particularly in the treble. The iFi one was more refined. The point about my son is that it wasn’t just my more experienceed ears that heard it, a newbie did too (and I didn’t lead him).

Two marketing sites, Phil. No measurements there that I can see.

“Interestingly” isn’t the word I’d use there :slight_smile: . Anecdotes are not convincing, you’re right.

I agree. Where are the measurements showing these power supplies that you are urging people to try are improvements?

What someone else may or may not have imagined they heard isn’t all that interesting to me, no matter how often it’s repeated. Measurements would be.

If you really want to influence people, you have to engage with them where they are, not where you want them to be. Come on, change my thinking about this! Show me some data!

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Bill

Like I said, I didn’t think you’d be convinced! Oh have another look at the Allo link by the way - there’s a link in the page to some meaurements.

Anecdotes or experience? I say the latter, you say the former.

“What someone else may or may not have imagined they heard”. No, heard, not imagined. Call it empirical data. And yes I know a sample size of two is not statistically relevant.

Hey, we both know none of the above is going to change your mind. So I’ll wish you a good weekend as I need to get out for a walk before it’s too late. Take care my friend

Phil

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This link, yes, but it’s not a comparison with a “noisy” alternative, just a graph of the Nirvana outputs. And, of course, it’s from a company which wants to sell me a power supply, so…

It’s not even that. No controls, that you’ve told us about.

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@ricgf, there’s an interesting thread on this over at Audio Science Review. The discussion shows where there are pros and cons for each approach.

My favorite justification for LPS in that thread is that they are better at slowing down lightning strikes.

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I’m going to try to explain this without getting too technical, and without trying to sell you anything.

DC power supplies have a job, and that job is to convert AC power (your wall) to DC power (what electronics usually need).

Both linear and switching power supplies do that task, but they accomplish it in using different methods.

The biggest “technical” difference is that linear power supplies use a large power transformer to do that conversion, and switching power supplies do not (they use more advanced circuitry that only became reasonable in the 1970s). I digress into these technical details only to serve as an anchor to your second question which I address at the end of this post.

The “linear solution” is nice because it’s a very clean (low noise) solution, but it’s expensive, heavy, and very inefficient (input power is converted to heat and not output power).

The “switching solution” results in an inexpensive, lightweight, and very efficient power supply. It also produces less clean (more noise) electricity.

Switching pretty much won over the world in the last 40 years, and it’s why everyone piece of consumer electronics has a little wall wart or tiny PSU inside the unit.

Nowadays, linear power supplies tend to be used where the noise from electricity could impact the device it is powering. For example, if your device had a high sensitivity sensor, the noise from the electricity could interfere with the operation of that sensor by introducing noise into the sensor’s output signal. If the sensor is critical to the operation of the device, using a noisy power supply could render the entire purpose of the device moot.

In audio, the digital-to-analog conversion and amplification are analog processes that could potentially be impacted by electrical noise. The rationale is that linear power supplies are “better” for powering these types of audio processes. There are things you to do to make them less susceptible to noise, but most proponents will just want to avoid the noise in the first place.

In modern times, switching power supply technology has become quite noise-free, while maintaining the many other benefits of a switching power supply (efficiency and size, but not cost). Many audio manufacturers, including high-end brands (like dCS) have been able to achieve noise levels equal or better than even traditional linear power supplies while maintaining efficiency and size. Note that there are still a ton of really noisy switching power supplies out there still, but the story today is not quite as clear as “linear clean” vs “switching dirty”.

It’s also worth noting that many linear power supplies out there, like the ones you can get inexpensively on AliExpress and eBay, are often poor quality. They are preying upon those who demand “linear”.

How much does all this impact your sound? That is highly subjective.

They often look the same, but if you look under the hood, you will see large power transformers that will sometimes look like this:

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Thanks, @Phil_Wright - my question was generic in the sense of understanding why people talk about them around here, and what the usual options for purchasing are.

My secondary question was: how can one even use them if virtually ALL devices already have a PSU?

And of course, tks a lot as well, @danny - this information is much appreciated. So I take it that, at least nowadays, there is very little advantage in using a linear PSU.

You can throw out the old and replace it with a similarly spec’d new power supply. Most DC power supplies in this space are externally located and connected to the device via a connector (barrel, or one of the DC IEC connectors). Think about something like your laptop’s power supply brick or your phone’s power adapter. All you have to do is meet the DC power requirements (voltage, minimum amperage) and have the right connector.

That’s one of the popular subjective takes on the subject. There are others.

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Most devices have additional on board regulation, eg, nucleus/nucs, so buying an expensive linear PSU to feed something with internal (switching) dc to dc converter(s) may be a dubious investment.

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