Do you think a wall wart power supply is good enough?

Switching power supplies do not operate at 60Hz. Their switching frequency is over a 100kHz and sometimes several MHz. Linear power supplies operate at 50 or 60Hz.

This issue may not be of consequence to most of these viewers, but wall warts, usb chargers, and more, play havoc on AM radio reception as well.

Switch mode doesn't care about line frequency.
If it is switch mode, it will likely be marked 50/60Hz
100 - 240 VAC.
Transformers in linear power supplies usually are rated at 50 or 60Hz, and exclusively 120 or 240 VAC, not both.

This is an interesting device. Do you have any suggestions for getting rid of hum that seems to come from a ground loop? I've tried isolating components to different A/C circuits, as well as using snap-on ferrite filters to the power and audio cables (with several wraps around the ferrite filter) and none of that seems to work. I was thinking to try some audio isolation transformer boxes, kind of like a DI box for PA work, but the good ones seem a bit pricey for such an experiment. I'd welcome  your thoughts and any from others here in the comments. Thanks for the video :)

I am not smarter than the manufacturer of my device. The fact is the first power supply for my AT-LPGO-BT died. I went ahead and bought a switchable one right away to determine the cause why the turntable stopped, suddenly! The solution worked, thank God.

A few notes of interest here:

As for the digital connection - S/PDIF - Officially, the Sony/Philips Digital Interconnect Format, but more commonly, Sony/Philips Digital Interface.  Can carry uncompressed 2-channel PCM or compressed 5.1.  It cannot carry lossless surround sound formats, thus why the newer HDMI formats for that purpose.  However, for simple 2-channel components like these, S/PDIF is plenty good enough, as it can effectively carry two channel at 24 bits/192 kHz sampling.

As for inserting USB connectors, we have a joke at work.  There are three ways to a USB connector goes - The right way, the wrong way, and the way you tried!  USB-C is so much nicer.

For my own setup, I've upgraded the power supply in my Eversolo DMP-A6 ME to a linear power supply, and I could tell an immediate difference.  Much quieter noise floor and noticed better, cleaner detail in the music.  As for powering the main system, I have a Panamax power conditioner that supplies very clean power, especially to the amps.  It even has a display showing the amount of amperage and volts of power draw.  If I have those amps cranked up, I can see some serious power being drawn.

The triggers are really nice.  Just press a single button and both the pre/pro and my stack of amps is powered on.  Even when I just just turn the TV on, it fires up the whole system as I do run my TV through my setup.

Is a power supply like shown in the video really necessary?  As correctly indicated in the video,  no.   It is definitely not required, but it really is nice to have.  I can tell a difference in my own setup when I supplied good clean power to it.  Much lower noise floor, which as a result, seems to bring out more detail in the music.  At the very least, it is nice to also have that extra bit of protection, especially when I am talking about components that costs a couple thousand dollars.  I did lose my Roku SoundBridge M1000 to a lightening strike years ago, though, which really p'd me off!  That was a music streamer back when the concept of a "streamer" was still a very new thing and well before Roku made the TV streaming boxes.  It also had a really cool and vibrant vacuum fluorescent display that could easily be seen from across the room.  Since replaced with a Pioneer Elite N-50 streamer/DAC (which also died), and now Eversolo DMP-A6 ME.  After that, I made sure I had good power protection in my system.

It's an external rectifier.  Old equipment incorporates the rectification inside the unit with either a rectifier tube, a selenium rectifier (looks like a big finned heatsink and smell like burnt garlic when it goes bad) and later a simple diode like a 1N4007 and a dropping resistor.  I get why they used them on things like slot car racing tracks and early LED calculators but never understood why they'd use them on high fidelity electronic equipment as I would assume a diode and dropping resistor inside a unit would be a much cheaper solution.  I suspect one of the reasons you have such a hard time picking up AM broadcasts is because of all the electroniccs in your home that use those noisy external rectifiers, not to mention other things like fluorescent lighting, PC's, etc all create noise that interfere with AM reception.  Some day you should take one of your battery radios outdoors at night, just as an experiment to a place like the middle of your back yard and see how the reception is there.  I bet you get something then.  Edit:  I also imagine that is why a lot of HAM operators have their equipment in a dedicated shack or shed is to cut down on external interference from noise making items in their homes.

I don't know....I have an LP70 and TT13 turntable.....I get no noise from either of those...why would I need this???

Did you actually play CDs through that stack. I'm not asking for any sound quality reasons, but because the Merak CD is speced to work with a 5v/2a supply and the USB on the PSU20 is only rated at one amp. Curious if that would function like that.

Things get interesting when you combine a linear power supply with a Class D amplifier. That’s because a Class D amplifier works similarly to a switching power supply. Nevertheless, even audiophiles with “golden ears” now acknowledge that Class D amplifiers offer sound quality on par with that of conventional linear Class A/B amplifiers.

I have a love/hate relationship with switch mode power supplies. Wall wart or not. Nice idea but the execution tends to be cheap and they do not last long. I have had to replace too many.

One I had to replace was for a Velodyne SMS-1. One day I noticed some hum coming from my subwoofer. Which I isolated to coming from the SMS-1. After cursing yet another failed SMPS and wondering how something that switches at 10s of KHz would be afflicted with 60Hz hum, I purchased a replacement.

I would prefer linear power supplies for most applications
More reliable and tend to not be so violent if they fail

Nothing wrong with Bose( got to say That )
I have a Bose sound bar that runs off an external power pack.  Lucky me, I also have a small amplifier ( not Bose) that can run off it. I thought.
It works but the noise produced by that power pack with the amp is massive.  Back to Belken , think that's its name

My lp120x has a wall wart. I have no hum or noise at all. 🤨
To me, this is more audiophile nonsense. No offense.

1:44 - One HUGE fault is that there is NO polarity standard for those type of barrel connectors!

No quality hi-fi components have wall wards, and generally great hi-fi components, show the internal structure, I also love attention to detail, but mostly on the internal 😂
Edit: Cheers from Copenhagen 🇩🇰