It can be used only with USB power in the most computer environment without connecting to the adaptor.
However, as it may not operate normally in a powerless USB hub, notebook, or low power computer where the power of a USB port is unstable, an adaptor should be connected. Be sure to use an adaptor if connected to the iPad or smart device.
※ If USB power is used, and volume knob is over 2 o’clock direction at the maximum window volume, sound begins to crush. Thus, when using a high impedance (over about 150Ω) headphone, connect to the adaptor for use.