Will external power supply and USB voltage add up?

[Barry_Sound]

Here is one thing I was wondering about.

Let´s say I have a DAC that is specified for 9V DC input but is also USB powered.

Will an external power supply with 9V output and USB (5V?) add up to 14V and is there a potential chance of exceeding what the DAC can handle in total voltage?

 

[MaxwellsEq]

I think all available DACs should handle this OK. They should be designed to select between one or the other.

 

[amirm]

If a DAC has external 9 volt input, then likely it doesn't use the USB for power, just data. Some do accept power from both but likely regulate the 9 volt down to 5.

 

[Andysu]

interesting usb and i noticed with my Dolby CP750 usb other no day , was i had a little voltage nib a voltage bite or felt some when turning the fader and my finger resting against the usb , should i feel a voltage ? the terminal pins are on the inside , so this was partly on the outside , shouldn't be grounded , and yes the mains plug inputs are all earth grounded , i guess it felt like 5 volt i googled usb voltage

 

[solderdude]

What you felt was not 5V but most likely some leakage of mains voltage.