ZOTL Ultralinear+

About the ZOTL Ultralinear+

The ZOTL Ultralinear+ is Linear Tube Audio's upgraded version of the original ZOTL Ultralinear power amplifier, built around David Berning's patented Zero-hysteresis Output Transformerless (ZOTL) topology and a high-performance switch-mode power supply. It is a push-pull Class AB stereo tube power amp that outputs 20 watts per channel into 8 ohms (about 22W into 4 ohms), using four 17JN6 Compactron-style TV sweep tubes as output devices and 12AX7/12AU7 small-signal tubes, all auto-biased NOS. The amplifier is optimized for real-world loudspeakers and can comfortably drive many speakers of roughly 88dB sensitivity and above, while retaining the low noise, wide bandwidth (8Hz-60kHz) and extended tube life characteristic of Berning's ZOTL designs. The Ultralinear+ revision incorporates Linear Tube Audio's factory "Plus" upgrade, adding roughly 100,000µF of extra capacitor storage and replacing key audio-path parts with high-end non-magnetic Audio Note Tantalum and Holco metal-film resistors, chosen per location, which improves tone, texture, and clarity across the frequency range. Connections are via a single pair of Cardas RCA inputs and WBT speaker binding posts, and the amp includes stereo/mono switching and comprehensive speaker protection circuitry.