I noticed with the Schiit Vali that even when it is turned off, the power supply (the plug that goes into the outlet) stays warm even with the unit turned off. Is this normal and if it is, why would the plug be warm even with the Vali turned off?
I would imagine this is true of most, if not all, of those devices that use those "wall wart" power supplies. The power switch is in the device being powered (the Vali in this case), and not in the power supply itself (the wall wart).
Whether any power supply remains warm with the thing it's powering turned off, depends on where in the circuit that power is turned on and off. There is power being supplied to your Vali whether it is actively on or not. That's because the power supply is an external unit, and there is nothing controlling it from within the Vali. So whether your Vali is using the electricity being supplied to it or not, the power supply is still converting wall current into whatever voltage the Vali needs. And yes, that means it's still drawing power, and your electric bill is going up, ever so slightly, with the Vali off.
To give a different example, suppose we were discussing a large home theater amplifier unit. Most of those have a power cord that plugs into the wall, and the power supply resides within the amplifier itself. A power supply is basically a large transformer with one side connected to the wall current, and the other side to a rectifier and filter capacitors, then the unit being powered. If you interrupt the wall current on the AC side of the transformer, then there will not be any power drawn to the unit while it is off. However, to accomplish that, you need a good sized relay that can withstand 120 or 220 volts (depending on your country), plus whatever current the transformer draws. That's a pretty good size device. If however, you are controlling power to the unit on the other side of the transformer (the device being powered), then you might not need such a large relay to switch power. A smaller relay means a cheaper device. However, it also means that you're paying to power the thing even when it's off.
Every wall wart in your home is warm, whether the thing its powering is on or not (if that's any consolation). It's not just your Vali. It could just as easily be your Magni, or your computer speakers, or your DAC, or your telephone, answering machine, portable TV, the list is probably endless.
One solution to this issue is to plug your wall warts into a power strip, and turn the power strip off when you're not using your devices. Then there won't be any "current vampires" robbing you of electricity.
With today's electronic power meters on your house, it's really easy to see this happening. Go away for a weekend and turn everything off in your home. You'll be able to still see power being used, constantly. That little power draw is the sum total of all of those wall warts, or other devices in your home, that were designed to keep drawing power from the wall socket, even with the device turned off. This can be a substantial drain if you have a spouse, children, and all of you own a shopping cart full of electronic devices.
For an even more interesting experiment, instead of just turning everything off, unplug everything from every wall socket in your house, and then go away for another weekend, and then examine your power drain at the local power company's website. You
should see no power draw (and if you do, call an electrician, there's something wrong).
