ZOTL40 Reference Upgrade Program


ZOTL40 Reference Upgrade Program

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As a ZOTL40 owner, we want you to have the best possible sound in your system, so we are pleased to offer an upgrade program for you to get all the benefits of the new ZOTL40 Reference at a fraction of the price.

Resistor Upgrade (Free):
Tube Upgrade:
Capacitor Upgrade:
Case Upgrade:
Add To Cart

Well, I didn’t expect the changes to be This Good! You really should have named it the ZOTL50. Just stunning...
— Peter, Happy ZOTL40 Reference Upgrade Customer

As you may know, we recently launched a major upgrade to the ZOTL40 amplifier, a product we’re calling the ZOTL40 Reference.

Why “Reference”? It’s that good.

We are offering multiple tiers of upgrade, one of which is free.

FREE Resistor Upgrade

  • LTA will upgrade the resistor values in your existing amp at no charge 

  • Improved bass and overall tonal texture, especially with high-efficiency speakers

  • You pay only shipping (both ways)

Additional Upgrades

In addition to the above, you can opt to have us do the following upgrades. If you do all of them, your amp will be upgraded sonically and visually to a full ZOTL40 Reference amplifier.

  • Premium Mundorf capacitor upgrade: $300

    • Improved dynamics, by upgrading the capacitor in the audio path to premium Mundorf film capacitors

  • NOS Mullard EL34 tube upgrade: $800

    • One of the best mid-range tubes on the planet, improves everything over the stock tubes

  • Chassis upgrade: $800

    • New chassis design, featuring low-resonance milled aluminum case designed by Fern & Roby

  • All upgrades: $1,710 (10% discount)

10% off a new ZOTL40 Reference amplifier

If you would like to purchase a new ZOTL40 Reference, we are happy to offer you a 10% discount off the retail price.

As an existing customer, you will also be placed at the front of the line for production and delivery.

Contact us to get 10% off a new ZOTL40 Reference Amplifier.

ZOTL40 Reference Amplifier

Linear Tube Audio is proud to present the ZOTL40 Reference amplifier. A worthy flagship and the most refined manifestation of David Berning’s ZOTL design.

The latest iteration of LTA's EL34-based amplifier, the ZOTL40 Reference includes a new chassis, component improvements, and is supplied with Mullard NOS EL34s that take this 50 watt-per-channel amp to a new level.


Curated to be the best

Careful component auditioning with a broad range of available loudspeakers elevate the ZOTL40 Reference amp to deliver the best results possible in a wide range of systems.

The best tubes on the planet

EL34 tubes are rightly revered for their tight bass, velvet mids, and smooth highs that allow for hours of listening without fatigue. The ZOTL40 ships with a matched quad of the best Mullard EL34 tubes on earth.

Constant improvement

Listening is the only way to improve an audio product, which is why we take customer feedback so seriously. We have some of the most knowledgeable and discerning customers in the industry, and their input is a key part of our product development process. The ZOTL40 reference amp is the kind of unbelievably good product that can only be achieved with careful development and experimentation over time.

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 ZOTL40 Reference 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 ZOTL40 Reference 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.

Made in the USA

Every LTA product is designed and built by hand in Takoma Park, Maryland, by a group of technicians who are also musicians, audiophiles, and music lovers. Some of whom have been with us since the company’s earliest days.

Quality assurance

The ZOTL40 Reference amplifier is hand built by technicians with years of experience building the complex ZOTL circuits. All our products are backed by a 2-year warranty and a 14-day no-questions-asked return policy.

What’s New in the ZOTL40 Reference Amplifier

We have been making the ZOTL40 (Mk II) for a couple years, and it enjoys a stellar reputation when using low sensitivity speakers such as electrostatics. Over the past year LTA has invested in design development and along the way found opportunities to bring fresh insights and refinements into every one of the products in our lineup, including the ZOTL40 reference power amplifier.

The ZOTL40 reference amp is the kind of unbelievably good product that can only be developed with careful experimentation over time.

Improvements in the ZOTL40 Reference amplifier include:

  • Careful component auditioning (review & final selection) with a broad range of available loudspeakers to elevate the ZOTL40 reference amp to deliver the best results possible for our clientele.

  • Premium Mullard EL-34 tubes are standard.

  • New chassis designed and built by Fern & Roby includes careful selection of materials and finishes plus grounding and shielding improvements.

The result is a significant improvement to the ZOTL40 Mk II that makes the ZOTL40 Reference an end-game component for guaranteed excellence in any presentation.

Purchase without fear or doubt. Like all Linear Tube Audio products, the ZOTL40 Reference Amplifier comes with a 14-day no-questions-asked return period and a one-year warranty.