Mini-stacks and the "Wall Wart" Struggle: Does PSU efficiency actually matter for the noise floor?

[tifipa2943]

I’ve been spending way too much time lately trying to tidy up my desktop setup. Like many of you here, I’ve gradually moved away from giant rack-mounted gear toward these incredibly high-performing "mini-stacks." While these small units measure brilliantly on the bench, the sheer amount of cable spaghetti behind my desk has become a total nightmare. It feels like every DAC, headphone amp, and streamer comes with its own proprietary, bulky transformer that takes up two spots on a power strip.

Recently, I’ve been looking into consolidating everything. I’ve been experimenting with using a single, high-quality 65-watt power module—the kind of compact, high-efficiency GaN supply you’d normally see for premium laptops—to run my entire desktop chain via some custom splitters. My primary goal was purely aesthetic to save space and reduce heat, but it really got me thinking about the engineering trade-offs we often overlook.

One specific point I’ve noticed in various teardowns is how modern switching supplies handle ripple. While a 65-watt module is incredibly efficient and stays cool, the high switching frequency is often touted as a benefit because it’s theoretically easier to filter out than the 60Hz hum of an old linear supply. However, in such a small form factor, I wonder if we’re just trading one type of noise for another that’s harder to measure without a high-end analyzer. I haven't subjectively noticed any hiss through my IEMs, but as we always say here, the ears are easily fooled.

Has anyone here actually bothered to put a high-density 65-watt switching module on an oscilloscope to see how it compares to the standard "brick" that comes in the box with most Chinese Hi-Fi gear? Are we gaining anything in terms of signal purity by moving to more modern power tech, or is it strictly a convenience play?

 

[RandomEar]

As far as I know, a higher switching frequency doesn't imply a higher ripple. Ripple is also typically measured using a 20 MHz bandwidth limit, so it doesn't really matter if you are switching at 50 Hz or 500 kHz - both is far away from your stopband frequency. Good phone/notebook charger GaN bricks are below 80 mV ripple (around 6:25) and they are super densely packed. So it's not a question of the form factor. The cheaper ones can reach 300 mV, though (same video, around 2:50). It's 100% a question of good design and cost. So you have to look at the individual PSU, see if the manufacturer specifies ripple and if not, if anybody measured it.

I haven't subjectively noticed any hiss through my IEMs, but as we always say here, the ears are easily fooled.

Well, if it's inaudible, is it really a concern? Ears are easily fooled, but more so when comparing sounds or interpreting speech. If you can't hear any noise, even when concentrating on it in a quiet environment - well, then there isn't any audible noise (above your hearing thresholds). You can test it on different days and at different times of the day to rule out some effects like a changing noise floor in the room which could mask it or you being exposed to a loud enviroment before listening. But other than that, I wouldn't worry about it too much.

An effect that might become problematic if you attach all your devices to the same PSU is that any noise coming back from the device power inputs now doesn't stop at the power brick anymore, but can travel between the devices. Fosi offers a V3 Mono bundle with one PSU for two amps and they had to add a DC filter in the Y-splitter power cable to suppress unwanted interactions between the amps. And even then, you can hear a hum if one of them is powered off and the other is still running. I agree that a single PSU means less clutter and is easier to hide, but it could be problematic if you attach a class D amp on the same rail as other devices.

 

[SSS]

Ripple and RF-noise depend much on the specific power supply model used. Switch mode ones may have ripple at the switching frequency, normally well beyond 20 kHz, also up to 500 kHz. Since there the 50 or 60 Hz mains input voltage is rectified and loads a capacitor this ripple does not influence the output voltage.
Conventional transformer power supplies can have various levels of ripple if not stabilized. Otherwise the stabilizer does not transfer the ripple.

 

[staticV3]

It feels like every DAC, headphone amp, and streamer comes with its own proprietary, bulky transformer that takes up two spots on a power strip.

If it does come with a bulky transformer, then that power module won't do you any good as it puts out DC whereas the transformer you want to replace likely puts out AC.

In the desktop Hi-fi landscape, you typically see four kinds of power supplies:

1. Built-in Mains PSU with a Mains cable plugged directly into the DAC/Amp/Streamer.

2. AC-powered with a bulky transformer brick included in the box (L30II, Element IV etc.)

3. USB 5V powered with no PSU included: use whatever SMPS (e.g. phone charger) you have laying around at home

4. >20V DC powered desktop chip amplifiers with their own SMPS units (Topping, Aiyima, Fosi etc.)

A power module like the one you linked can only really be used for #4, but realistically only for a single device as supply voltages vary greatly between devices

So in the end what's the use case/point here?

Edit:
The one use case I can think of is if all of your devices happen to be DC-powered, then you could feasibly power them all off a single beefy desktop charger like the Nexode 300 or Nexode 500.

You can then plug in a bunch of this kind of adapter cable and select the right output voltage for each device:

Up to 48V with the Nexode 500, enough for beefy desktop Amps.