Underpowered using different usb-cables?

so I get very different reactions from using different usb-cables.


Both times they are connected to a typical usb-powerplug going into an electrical plug.

With some the device is underpowered and xrunnin’ like crazy. With others there seems to be no problem.
Yesterday I was in the studio with the zynth. It was underpowered and had so many xrun’s that with two miditracks being played through zynaddsubfx the clicking would make it un-recordable. I’ll try going back tomorrow with a different cable to see if there is a direct relation between the x-runs and the power.

Anyone else experiencing this?

Yes, high impedance power cable will limit current and create a potential difference (voltage drop) across the wire. This can result in a voltage at the Pi less than 5V. The Pi reacts by reducing CPU power and hence lower performance. I encounter this with some jumper cables between my UPS and Pi header. I am yet to fix this with thicker cable and better quality crimping. Resistance will increase if there is poor connection and with thinner wire.

Same experience here when using an extension cable.

Always had those problems with very-chinese cables… the worst cable I had had a 1.5V voltage drop at 1.5A.

Since then, I test every single cable I want to use as power cable, and ditch it if it drops more than 0.2V@1A. Better safe than sorry.

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Ok then clearly mini-usb cables do vary a lot in quality and power output. Thanks for enlightening me guys!