-3

My device comes with a wallwart rated at 12V dc/1.5A and the manufacturer specifically warns not to use over 12V dc. Is it safe to use a switching power supply rated at 13.8V dc/30A?

ocrdu
  • 8,705
  • 21
  • 30
  • 42
nicco
  • 11
  • 1
  • 6
    "manufacturer specifically warns not to use over 12vdc" - isn't that answer enough? Go above at your own risk. – Mat Nov 14 '21 at 19:44
  • 3
    Entirely depends on the device. You know what the device is; we don't. Use its manufacturer's recommendation. –  Nov 14 '21 at 20:32
  • The device is an Aiyima T7, a mini preamp. Some fellow audio enthusiasts reported a big improvement in the sound when they switched to some Pyramid psu's which are rated at 13.8vdc with various amperage and been doing it for years with no issues. I happen to have one that I was hoping to use. – nicco Nov 15 '21 at 01:41
  • 1
    Forgive me for saying so, but this sounds like the audiophile equivalent of pouring cheap vodka through a Brita filter. From the Amazon page (which also specifically tells you NOT to use more than 12V input), it looks like they just ship it with a very cheap switching power supply, which is probably undersized. My guess is that if you use any sort of reputable 12V supply you'll see the "big improvement" everyone else is seeing. – vir Nov 15 '21 at 03:36

1 Answers1

2

Short answer, not really. Maybe seek a cleaner 12V / 1.5A supply instead if you're trying to get better performance from the device.

Let's unpack this a bit.

13.8V is a supply meant to mimic a standard ‘12V’ automotive source. It's sometimes used to power car stereo and other stuff from wall power. That also explains the big amperage.

Now about your device. A ‘12V input’ rated device of necessity has to have some tolerance, as it’s impossible to achieve exactly 12V with any supply. What would be a reasonable tolerance then? Hard to say. At minimum, +10% max over nominal, so 13.2V, would be ok as a design spec for max input.

However, 13.8V nominal is already +15% over 12V. If that 13.8V supply itself has a tolerance of +10%, that would be as much 15.2V as worst case, a whopping 27% over 12V nominal.

With that much over-voltage you’re counting on the device design being very forgiving. Unless you have direct knowledge of the device (like a schematic) and understand power supply designs you’re taking a risk.

On the other hand, their explicit caution to limit the power supply to no more than 12V gives a strong hint that they're not confident in the thing being robust to higher voltage.

Now, back to that automotive 30A supply. Another concerning thing is its current. Again, if your device has a very cheap design it could be counting on the external supply to limit its output in the event of a short. Using a 30A supply in place of a 1.5A one is asking for trouble: if your device fails with an internal short, it could catch on fire.

Assuming you are willing to risk the higher voltage as above, at least add a fuse or other current limiter.

hacktastical
  • 49,832
  • 2
  • 47
  • 138