Someone earlier in the thread asked about RCA jacks out, this is from Amazon.ca product description: "This design, unlike some others, allows the tube to be active regardless of which input is in use. The result is great tube sound from your iDevice, Android device, any MP3 player, CD or DVD etc. using the RCA inputs, and from your computer using the USB input. Additionally, the signal from both the USB and RCA inputs is available from the RCA out jacks for use as a pre-amplifier or tube buffer. "