Go to the software's settings/options menu and select your external USB interface as both the primary input device and output device.

It turns your PC into an audio generator, THD analyzer, and wow-and-flutter meter.

Before testing external gear, connect the physical outputs of your audio interface directly to its inputs using a short cable. Turn on the T-100 software oscillator and verify that the input meters register a clean signal with zero distortion. This establishes your baseline floor. 2. Measuring Wow and Flutter on Tape Decks

Measures signal-to-noise ratios using industry-standard weighting filters. Modern Nak T100 Software Emulations

If you are looking for a downloadable program that performs the same functions as a Nakamichi T-100 (analyzing frequency response, bias, etc.) for tape deck calibration but using a modern PC sound card, you want software.

The original developer hosted the file on now-defunct forums like Tapeheads.net and AudioKarma.org . The most trustworthy version is typically named or NakT100_Setup.zip .