What is a USB Audio Interface

An audio interface connects your standard large condenser cardioid microphone to your computer and provides phantom power for the mic. Phantom power must be switched off for other microphones. A digital audio signal is sent to your computer USB or Firewire connection. At the same time a signal is sent back with audio for monitoring headphones, the goal being zero latency.
There are a couple of other connection scenarios that we won't get into here, because they go with much more expensive equipment, usually. We can get great results without that expense.

Focusrite Scarlett 2i2 interface
Includes two microphone preamps. If you are new to this you may be wondering about phantom power. Large diaphragm condenser mic's require phantom power to operate which is provided by this interface.

Most PC and Mac computers come equipped with USB ports and FireWire is a Mac invention. The Focusrite Scarlett 2i2 interface uses USB output

Bit depth and sample rate.
Bit depth has a huge impact on your sound. if you work at 16-bit, the quieter sections of your audio will tend to be noisy.

With 144dB of range, 24-bit audio is considered the professional standard

Sample rate. Each sample is a digital snapshot of the captured audio. the 44.1kHz sample rate is theoretically capable of reproducing frequencies as high as 22.05kHz. Most audio is done at 48kHz, 96kHz, or even 176.4 or 192kHz.

Working at 24-bit/44.1kHz can be done, and some USB mic's use that output. Better is 24-bit/96kHz. Higher sample rates and bit depths use more disc space.

Under $100.00USD- Focusrite Scarlett Solo USB 2.0 Audio Interface, 2-in/2-out, 24-bit/192kHz, with 1 Mic Preamp, 1 Instrument Input, USB Bus Power, and Bundled Software - Mac/PC

Or the Focusrite ITrack solo,USB / iOS Lightning Audio Interface compatible with firewire connections to Mac and Ipad.

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Rode NT1-A Recording Studio Kit with USB / iOS Lightning Audio Interface, Desktop Stand, and Headphones $379.95

B&H # RONT1ACRSLCK (B&H Kit)

Condenser Microphone w/ 1" Diaphragm

Cardioid Polar Pattern

Transformerless Output Stage

USB / Lightning Audio Interface