Advisory tale on equipment power consumption, particularly Dac's.

[Firebottle]

I have recently bought a 2nd hand Dac that runs on 12V.
It came with a switching power supply in the form of a wall wart.

The PSU says 12V 1.5A output so one might think that to run from a linear PSU I would need a 12V 1.5A LPSU.
Wrong! The included PSU is probably the cheapest one that the manufacturer could find of the correct voltage.

I have come across this on numerous occasions where the switching power supply is well overrated for the equipment it is intended to supply, be it 12V or 5V supply.

The only way to reliably find out how much power is actually required is to measure the current consumption.
Probably the best way to do that without getting inside the equipment or cutting the PSU lead is to make up a break out lead so an ammeter can be connected in series.

For the case in point with the new dac it actually takes 0.3A tops, so I am running it from a 0.4A LPSU.

[Macca]

I use a mobile phone charger to run my Topping, I think it's 0.5 of an amp no idea what the DAC is rated at but it works.

[Firebottle]

I'm guessing your dac didn't come with its own PSU? If it can be powered from USB then it will likely be a fair bit less than 0.5A which is the common limit for USB power.

Just plug into a USB socket, or as you are doing use a 5V charger.

[Macca]

I'm guessing your dac didn't come with its own PSU? If it can be powered from USB then it will likely be a fair bit less than 0.5A which is the common limit for USB power.

Just plug into a USB socket, or as you are doing use a 5V charger.

No, they don't supply a PSU with it.

[Lawrence001]

I'm guessing your dac didn't come with its own PSU? If it can be powered from USB then it will likely be a fair bit less than 0.5A which is the common limit for USB power.

Just plug into a USB socket, or as you are doing use a 5V charger.

USB C limit is 3A without power delivery, with that it's much higher but that tends to be for laptops and other higher power devices, or certain mobile devices with a turbo charge facility.

[JimC]

If the DAC only consumes 300mA, the original PSU, even if capable of supplying 1.5A will not be delivering 1.5A into this particular DAC, only 300mA.

Especially an SMPS, a 1.5A capable supply, supplying 300mA will only itself be consuming very little indeed from the incoming Mains.

I am not fully understanding your point.

[Firebottle]

OK James, it's not about efficiency it's about noise.

Any SMPS creates noise and it is not welcome in any audio equipment. That is why a great many 'audiophiles' change to using linear power supplies.

The point of the exercise is to find out exactly the direct current required so a suitable LPSU can be used.

[JimC]

Fair enough. I understand your point now, but it wasn't clear from your original post.

I hate SMPS's, from a noise perspective and having to fix them !! Hateful things.

[majex45]

Fair enough. I understand your point now, but it wasn't clear from your original post.

I hate SMPS's, from a noise perspective and having to fix them !! Hateful things.

I know what yoou mean. It's the BELT you get from the 450V electrolytic that gets me if I forget to discharge it first.