Linear Tube Audio ZOTL Ultralinear power amplifier


The Linear Tube Audio ZOTL Ultralinear ($6,800.00) is the latest ZOTL amplifier design by David Berning, utilizing his Zero-hysteresis output transformerless audio design and his unique power supply. The  ZOTL Ultralinear amplifier outputs 20 watts per channel using 17JN6 tubes, a Compactron-style TV sweep tube that can't be easily used in traditional transformer-coupled amplifier designs. The ZOTL circuit is able to take advantage of these great-sounding, under-utilized tubes, and in this case, does so in what can be considered the only ultralinear amp without traditional output transformers.

David designed the amplifier specifically for high efficiency speakers. A balance between triode and pentode mode, the ultralinear topology delivers a less forward presentation which is "more pleasing to listen to".  The ZOTL Ultralinear delivers accuracy, detail and realism. Pianos sound like pianos. The bass is controlled but fluid. Very transparent, no hum and very dynamic.

The power supply is an advanced switching supply optimized for audio that only David Berning deploys.  

All the benefits of ZOTL technology, including 3 times the tube life, 1/3 the heat, a super wide frequency response of 8hz -60Khz, and a under 2 ohm output impedance to play nicely with all speakers, are all included. There is also a sophisticated speaker protection system to prevent damage to the amplifier and speakers if there ever was a tube issue.


Fern and Roby Audio designed the casework featuring front and rear panels milled from slabs of aluminum, Cardas RCAs, WBT copper binding posts, front panel industrial toggle switch, and a stereo mono switch with all markings laser engraved.

David Berning designed, hand-built by Linear Tube Audio, with casework by Fern and Roby.  

Plays nicely with others

The ZOTL Ultralinear was specifically designed with high-efficiency speakers in mind. Yet a super-wide frequency response and less than 2 ohm output impedance means it plays nicely with all speakers. 

Stereo + mono, at the flip of a switch

The ZOTL Ultralinear outputs 20 watts per channel. Need more power? Like all of our power amplifiers, it can be used as monoblock or stereo amps at the flip of a switch.

Unique tubes, unique amp

The ZOTL Ultralinear uses 17JN6 power tubes, a Compactron-style TV sweep tube that can't be easily used in traditional transformer-coupled amplifier designs. The ZOTL circuit is able to take advantage of these great-sounding, under-utilized, inexpensive, and widely available tubes.

Never buy another set of tubes

Most tube amplifiers run through tubes every 1,000-2,000 hours. That sounds like a lot until you consider that we estimate tube life for our amps to be in the 10,000-20,000 hour range. Why? Because we use ⅓ the current through the tubes, which results in lower heat and dramatically longer tube life.

Tube tone + solid state detail

Traditional tube amps are known for their liquidity and linearity, but their “warmth” masks details and can sound thick. Solid state amplifiers give you that detail, but can be “clinical.” ZOTL amplifiers give you the best of both worlds: beautiful tube tone with the clarity of solid state (while being entirely tube-based.)

Looks as good as it sounds

The low-resonance aluminum chassis of the ZOTL Ultralinear amplifier is designed and manufactured in Richmond, Virginia, by the award-winning industrial design crew at Fern & Roby. Sturdy toggle switches and machined aluminum front and rear panels exude quality.

Patented perfection

The ZOTL Ultralinear amplifier is based on David Berning’s patented ZOTL technology, the only advance in tube technology since the 1950’s. For a technology to be patented, it must be deemed “new, useful, and non-obvious.” We think that sums up our approach quite nicely.

Premium components = premium sound

If you use cheap, generic parts, guess what kind of sound you’ll get? That’s why we use only premium, name-brand components. Belleson regulators. Ohno OCC wiring. Vishay Dale resistors. Mundorf caps. Typically, these are names you’ll only hear in amps that cost $10k or more.

Tube complement: Two 12AU7 and two 12AX7 input tubes, four 17JN6 power tubes - Autobias for all tubes. All tubes NOS.

SPECIFICATIONS
  • Inputs: One pair L & R Cardas RCA
  • Outputs: One set of stereo WBT speaker binding posts
  • Amplifier class: Push-pull class AB
  • Power output: 20 watts channel 8 ohms
  • Sensitivity: 1.2V RMS for 20 watts output
  • Frequency response: 8hz to 60khz - +0, -.5db
  • Output impedance: 1.6 ohms
  • Input impedance: 50k
  • 100V / 120V / 240V operation: Auto-switching
  • Hum and noise: 94dB below full output (measured between 20Hz-20kHz)
  • Gain: 21db
  • Stereo/Mono: Switchable Stereo-Mono
  • Dimensions: 17 inches (43 cm) wide, 5 inches (12.7 cm) tall, 13.875 inches (35.2 cm) deep
  • Weight: 17.5 lbs or 7.9 kg