Harold L. Black’s Classic Paper “Stabilized Feed-Back Amplifiers” appeared five years after he invented the feedback amplifier and four years before the patent was finally issued. Black’s paper shows the advantages of negative feedback in reducing harmonic distortion, increasing the bandwidth, and maintaining robust performance using primitive vacuum tubes. It also introduces a nomogram similar to the well-known Nichols Chart. In an effort to gain a better understanding of the unerlying mechanism of feedback, he enlisted the aid of H. Nyquist who responded with his famous paper, “Regeneration Theory.”