Established in 1974, The David Berning Company manufactures vacuum tube audio amplifiers based on an unique Impedance Converter that replaces the traditional audio power output transformer and greatly extends and improves amplifier performance. We call our technology "ZOTL" for Zero-Hysteresis Output Transformerless.

Operating at a fixed high-frequency without traditional audio output transformers, the ZOTL Impedance Converter eliminates the frequency-dependent performance limitations inherent in all transformer coupled tube amps.

Berning amplifiers using the ZOTL technology exceed the performance of traditional OTL tube amplifiers by properly matching the tube impedance to that of the speaker. Berning amplifiers depart from traditional OTL amplifiers in that they do not require a large number of hot power tubes to supply adequate current for driving speakers.

Berning amplifiers convey the musical transparency of tubes without the limitations imposed at the frequency extremes by audio output transformers. This limitation at the frequency extremes is a major contributing factor to what some negatively call "tube sound". ZOTL extends the desirable musical transparency of tubes to the frequency extremes and provides the quickness of the high and low frequencies that are cherished by those who prefer solid-state amplifiers.