Linear Power Supply vs SMPS

This thread was propted by discussions on another thread.

It’s a commonly held belief in the audio community that in general the SMPS’s supplied with much equipment these days are noisy and detrimental to performance and replacing them with a LPS yields an improvement.

However, there are those that dispute this. Two specific instances from manufacturers:

  1. Chord Electonics say that there is nothing to be gained from replacing the supplied SMPS on their Qutest DAC with a LPS. More than that they actually warn against doing it.

  2. The instructions that come with the EE8 network switch state that a SMPS was chosen as it contains specific filtering and that no LPS could be found that was fast enough. In effect the SMPS is integral to performance.

This has got me wondering - and worrying! My own experience is that when I replaced the supplied SMPS on my BT router there was a significant improvement. Likewise when I bought a Plixir LPS for my Melco N100 to replace the supplied SMPS.

I’m now questioning this. We all know that sometimes what can seem for all the world to be an improvement can turn out in the fullness of time to be just different, or even in some ways worse.

I know that in theory a well-designed SMPS shouldn’t be inferior to a LPS. But in practice they all seem to be… Or do they?

So my question is “Has anyone found that replacing a supplied ‘cheap’ SMPS with a LPS has actually resulted in a decrease in performance?” And if so, in what way specifically?

Many discussions on many Hifi forums about this.
There are unrelenting zealots of both LPS is best and the decent SMPS is best camps.
My experience leads to the decent LPS beats cheap wall wart SMPS every time so far but that a well designed SMPS (e.g. Chord Electronics) needs a very expensive LPS to beat it.

Hope this helps, BF


Don’t… be happy.

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Those are very telling statements!
But certainly worrying is not justifiable.

(Discussion of trying to ensure reliability of assessment in listening tests which by their nature are subjective, e.g. by minimising risk of psychological influences, is going beyond the theme of the thread and so this is not trying to invite discussion.)

I don’t doubt a well made LPS beats a cheap SMPS. That said, IME, a well spec’d SMPS can be on par and for sure is able to get low ripple levels that LPS can only dream of, remember LPS regulators can be a particular problem.
I have FRIWO (German made medical grade) SMPS’s on both wireless hub and switch. These are mounted on their own power strip and I have this and each SMPS unit clamped with frequency specific ferrites on both AC & DC sides, plus a RA “silencer”. This seems to keep most of the line noise suppressed as measured by my Fluke o’scope.
……. and happy to say no more experiments required.


No. Hypex has chosen SMPS over LPS for their Class D amplification and that was a choice made by comparing the two extensively. In both cases, they manufacture the power supplies themselves.

As usual ‘it depends’. Why everyone always wants to be one and only one solution the answer beats me, but it leads to futile debates.


Please don’t misunderstand me. I’ve absolutely no doubt at all about the improvements I heard. What I am now questioning is if there were/are any downsides which I wasn’t aware of at the time. Sometimes it can take a while to become aware of these, as one is overwhelmed by the improvements.

All academic really I suppose. If it sounds better then it is better, downsides or not.

Presumably, you can just swap them back again and then decide?

I once read that the stock SMPS of my Squeezebox was noisy and not as good as a LPS, so I bought a nice one on eBay and replaced the SMPS. I wasn’t able to hear a difference. My apartment is entirely lightened with modern LED bulbs, and they should be terrible. But my system still sounds excellent to my ears.
BTW I don’t have the SqueezeBox anymore; I think it was the bottleneck, not its PSU…

If large transformers were not the absolute icon of all self-powered Naim gear, I suspect that they would have developed excellent SMPSs… If they don’t have already.

It’s not that I notice anything amiss in the performance. My concern was really prompted by a comment from another poster that a LPS on his EE8 switch slowed things down. I’ve no doubt at all that the LPS on my router is an overall improvement so it will stay.

BUT, it has got me wondering if still more performance could be had by using a much higher quality SMPS - would this avoid any potential downsides of a LPS whilst retaining it’s advantages? I think I’m becoming a little obsessive over this…

My wild guess is that Chord claim this to reduce RMA related to people messing around with power supplies not compatible with their product causing it to fail. There is no question that my Farad3 sound better than the original SMPS on my EE8. If Chord would claim that is wrong I would be worried about Chord products performance in general.


Spot on Blackbird


Antipodes Audio is another company that advocates good quality, well implemented SMPS. I’m sure their are others.

The marketing advantage would appear to go to LPS, which, from what I can see, gets a lot more hype, so I don’t see any good reason why a company that makes power supplies would promote SMPS if they did not believe in it.

OK, but it really depends on what you mean by better. A post on another thread claimed that it sounded tonally nicer with a LPS, but that it sounded less organic and slower. Obviously all this is open to interpretation and of course will be system dependant. But it does raise the question of whether a LPS is autimatically a better choice.

I wouldn’t expect Chord to claim such a thing just to prevent damage/returns. If they wanted to do that why not simply state that replacing the supplied power adapter will void your warranty and Chord cannot carry out any associated repairs?

Well Hypex make the class D boards but it’s up to the manufacturer how they choose to implement it.

I just borrowed a TEAC AP-505 power amp that uses Hypex core. TEAC drive the Hypex with a linear toroidal transformer.

Going back to the OP’s question though, it’s a bit like asking whether electric is better than petrol engines. I mean, you could choose anything in that scope. If you choose a old milk float with 10 car batteries, no it’s not. If you choose a Tesla against Robin Reliant, then yes it is.

The thing with power supplies is when both are cheap, LPS wins hands down. But when they both cost proper money it very much becomes horses for courses. In terms of emitted EMI, even cheap SMPS measure good. Certainly, in my measurements, better than LPS. In terms of mains pollution, there will be so many SMPS connected to your supply both in your house and neighborhood it’s hard to single out one culprit.

For anyone that thinks high end gear with SMPS pollutes their mains, I’d ask them to get out their high voltage isolating probes, an RF band (at least 200Mhz) oscillascope and prove it.


A super summary.

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Now that we are talking about LPS.
What are your opinions on…
Sean Jacobs DC3 LPS
2*12V 5A.


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Now there is someone who knows how to design an excellent and very expensive LPS.

I have wondered more than once about using one of his DC4 supplies on our Chord DAVE but really don’t want to add yet another box to the already ridiculous number of boxes in our streaming system.

Coming at this from a different perspective, do we know of anyone who makes SMPS as expensive as the premium LPS of Naim, Sim Audio Moon or Sean Jacobs? I haven’t seen one, even from Linn. Perhaps Chord Electronics is closest with its Ultima power amps.

If one throws enough money at a well engineered solution, it usually comes out among the very best. This has been the case with LPS. It would be great to see someone do the same for an SMPS.

Best regards, BF


Interesting that Linn and Naim have taken diametrically opposed approaches to power supplies - Linn using exclusively switching supplies, Naim using linear power supplies.

The new stuff from Naim contains both types.