Power direct from the wall, or Power Conditioner?

[f1eng]

Given that a piece of hifi is designed to be driven from AC mains any competent designer should make it immune to any typical mains shortcomings.
I would consider any piece of mains powered kit which needed any sort of power conditioning to perform correctly to be defective.
Anybody who worked for me designing mains powered kit which needed any device between it and the mains to work properly would be looking for another job.
I consider Devialet good and competent engineers so it follows that any gain in performance by attaching an expensive accessory to its mains socket is almost certainly the placebo effect, which is real enough if one is susceptible.

OK, I'll bite. Just what do you mean by "any typical mains shortcomings"? The 2 usual mains shortcomings are incorrect voltage and noise on the line. What levels of both would you think it was reasonable for a designer to deal with in their power supply design?

The mains voltage here in Australia is supposed to be 230 V. Where I live it's rarely below 240V and often over 245 V, sometimes over 250V. Most components here are made overseas and I don't know what typical line voltage ranges are elsewhere but I suspect there are places with even greater variation than here.

When it comes to noise, what's the typical range of noise the designer should deal with in their design?

Finally, since you said that "Anybody who worked for me designing mains powered kit which needed any device between it and the mains to work properly would be looking for another job" I could draw the conclusion that you believe that designers should ensure that their components should never require the use of a power conditioner regardless of the state of their incoming power. There's a difference between ensuring a product is immune to "typical mains shortcomings" and ensuring that a product never needs any device between it and the mains to deal with mains shortcomings because, as a simple matter of fact, the set of shortcomings which can be classed as "typical" is always going to be smaller than the set of shortcomings encountered in actual situations because you can't have "typical shortcomings" without also accepting that there are "atypical shortcomings". If you want to demand that components never need the benefit of a mains conditioning device, then you are expecting the designer to deal with more than just the typical mains shortcomings, you're expecting them to deal with absolutely every mains shortcoming.

Designers can deal with every mains shortcoming but that comes at a price and that price is much more expensive components. In addition, every component you buy has to have the same ability to deal with every mains shortcoming possible. In my view it makes a lot more sense given the variability for mains variation from location to location, for components to be built to deal with some reasonable level of mains problem and for people to use mains conditioners of some kind where further correction of the mains supply is required because it's probably going to end up being less and more convenient for the customer to buy one conditioner capable of dealing with unreasonable/atypical levels of mains problems which can supply several components. That means that people who live in locations where mains problems fall within a reasonable or typical range don't have to pay fo their components to be capable of dealing with a level of problem they're never going to experience and that those people wo do have more extreme problems only have to pay for a device to deal with those problems for the components they wish to protect from those problems.

It's a great idea in principle to expect the designer to make their products immune from all problems but the customer has to pay for that and a lot of customers end up paying more for a level of immunity they don't need, and everyone ends up paying for that level of protection in the cost of every component they buy, regardless of whether or not they even want it for that device.

I'd rather see designers come up with power supplies that deliver reasonable results and let anyone who wants a better result have the option of buying an add on device which delivers whatever level of improvement they either want or can afford.

Don't buy it.
Are you thinking a huge number of hifi equipment fanatics are all unlucky enough to live in places with appalling mains supplies?
Or do you think most expensive hifi all has inadequate power supplies?
Makes zero technical sense to me.