I have a friend that swears he hears a difference, but I personally don't, and from a theoretical perspective you shouldn't. The input voltage goes exactly three places in most of my pedals:I’ll be getting a more in Tuesday and wanted to ask when powering with a cioks7, if the 9v 650ma or the 12v 500ma setting has any behavior differences for anyone? Thanks.
- The tube heater
- The high-voltage power supply
- The LED(s)
The high-voltage power supply is what we call a regulated power supply, which means it measures the voltage that it's putting out (feedback) to ensure that it's actually putting out as much as it's supposed to be. More, like all of my SMD pedals, is set to run around 235V or so (I think I read 237 on the last one I poked). The high voltage power supply will output 235V regardless of whether the input voltage is 5V or 20V. Higher input voltage does not mean higher tube plate voltage.
You may notice your LEDs light a little brighter at 12V.

