Will I Need an External Analog to Digital (A-to-D) Converter?
This question came up recently. If you are using one of the previously mentioned turntable "kits", these come with a turntable that has a USB plug on the end of the turntable's cable. Plug that in to one of your computer's USB ports, load the software that came with the kit and you are ready to go. The turntable has electronics built-in that convert the turntable's analog signal into a digital signal that feeds the USB port.
In my case, I am using my own audiophile-grade turntable. To get the analog signal from the turntable into the computer, the signal must first pass through a stereo receiver that has a "Phono" input. Then, a connection from the receiver's "Tape Out" to the computer's analog "Line In" jack is made. This eliminates the need for an external analog to digital converter that would feed the computer's USB port. A lot of people are unaware that most computers have such a "Line In" jack. It's almost always on the back of the computer and it is often a combination jack; one jack accepting either a signal from a microphone (very weak) or a "Line" source (stronger). The selection of which source the computer anticipates, microphone or line level, is made in the computer's audio settings. If the default is for microphone and you plug in a line level signal, it will likely be too strong a signal and cause distortion.