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NOTE: Easy Pay/ Splitit cannot apply to Linear Tube Audio products.
We can only sell these products to customers in the USA.
All Linear Tube Audio products are hand made to order. Please contact us for lead time.
14 Day In-home audition/ return. Period begins when you receive the product. The return must be requested by the 14th day and must be in perfect - like new condition.
Before we get into the details of this product, we need to cover two things...
1. Time for orders: The LTA products are hand made to order. Please allow 3 to 4 weeks for production.
2. The differences between the ZOTL40 Reference and ZOTL Ultralinear amplifiers: The ZOTL40 Reference and the Ultralinear both have the magic, realism, and 3D soundstage inherent in their patented ZOTL technology.
Both amps are fast, fluid and do an excellent job of reproducing the pace and punch of the music. Likewise, both amps have the black background, high clarity, accuracy, realism, and dynamics that fool your brain into thinking the performers are in the room with you.
The Ultralinear is a little more relaxed, more refined and a little less forward presentation (more noticeable with higher efficiency speakers). Despite having 20 wpc, it has very strong bass. The Ultralinear has a little more detail than the ZOTL40, and can rival any solid state amp as far as detail goes.
The ZOTL40 produces 40 wpc and uses Mullard EL34 tubes, which is one of the best midrange tubes ever invented. It has a little less detail over the Ultralinear yet a very solid midrange and punch.
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 EL-34s that take this 50 watt-per-channel amp to a new level.
“This amp plays any type of music with an unconstrained ease, and can be listened to for hours on end without fatigue. While the convincing three dimensional staging, and densely rendered imaging are fabulous, in my opinion, it is its flowing musicality that is the Z40’s true star-turn. ”
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.
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.
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.
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.)
“The ZOTL40 Reference manages to tip-toe the line between a classic tube sound, and a modern, solid-state A/B amplifier; and does so while being dead silent. Yep, you read that correctly. Silent.”
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.
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.
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.
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.
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.
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.
Staging is layered, dimensional, and expressive; with a noticeable ability to render a sonic presentation of venue / studio space. Bass is tangible, tonally accomplished, and powerfully deep. Treble is very good, with a complete lack of grit or glare. Midrange is delightfully musical, and realistic. Tone is uniformly excellent throughout the frequency spectrum. This amp plays any type of music with an unconstrained ease, and can be listened to for hours on end without fatigue. While the convincing three dimensional staging, and densely rendered imaging are fabulous, in my opinion, it is its flowing musicality that is the Z40's true star-turn.
LTA amplifier owners have found great enjoyment using their amps with a variety of speakers outside of the below ranges. The below are guidelines, not rules.
Critical listening environments: 85db sensitivity and above
Smaller rooms / lower volume levels / non-critical listening: 80db sensitivity and above
If you have questions about your specific speakers, chances are someone we know has tried them. Don’t hesitate to reach out with questions about your specific setup. Also, don’t forget we have a 14-day no-questions-asked return policy.
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.
Printable Owners Manual: Click Here
Sensitivity: 1.2V provides full output
Output impedance: 1.6 ohms
Input impedance: 50k
100V / 120V / 240V operation: Auto-switching
Hum and noise: 94dB below full output (measured between 8Hz-60kHz +0/-0.5dB)
Gain: 23db
Power output with 4-ohm load: up to 51W, 0.5% THD
Power output with 8-ohm load: up to 46W, 0.5% THD
Frequency response (8-ohm load): 8Hz to 50kHz, +0, -.5dB
Amplifier class: Push-pull Class AB
Net weight: 15 lbs
Dimensions: 17 inches (43 cm) wide, 5 inches (12.7 cm) tall, 13.875 inches (35.2 cm) deep
Finish: Aluminum case
Tube complement: two 12AX7s, two 12AU7s, & four Mullard NOS EL-34s - No adjustments – tubes are auto-biased
Many tube amplifiers have a sound described as "warm," "tubey," or "round". This sound can be very nice to listen to. However, it is the output transformers that produce the "warmth" or the tone of the sound, and it is actually a type of distortion, though pleasant. The detail of the music can be lost in the "warmth." There is no doubt that many people love the warmth of what they think is the tube, but is actually the transformer.
The ZOTL amplifiers do not have the thicker, warm tone that many tube amplifiers have. They still have the liquidity and linearity of tubes, but without a transformer's tone.
ZOTL amplification achieves neutral accuracy without coloration. This achievement is supported both by listening and through measurement.
Switching immediately from other tube amplifiers (and solid-state amplifiers designed to be warmer) to a ZOTL amplifier can often feel like something has been lost. What is actually happening is more akin to adjusting the focus of a lens: an increase in clarity accompanies a reduction of haze. While haze can feel like "body" or "weight" that is no longer there, as you adjust to the ZOTL amplifier you realize you are hearing the more accurate weight and body of what you are listening to, and the consistency in performance over varying impedances will allow you to experience this accuracy throughout the frequency spectrum with many different speakers.
ZOTL amplification's neutrality is also transparency. As source components increase in performance, ZOTL amps continue to reflect this, scaling up indefinitely.
Considered to be one of the world’s foremost amplifier designers, David Berning is among the elite in his field. A formally trained physicist, David’s unique perspective has invaluably colored every solution he’s designed for classic audio problems. After 20 years of designing and manufacturing tube amplifiers, David Berning turned the technology on its ear when he invented ZOTL (Zero hysteresis Output Transformer-Less) architecture in 1996.
So radically different from anything around at the time, ZOTL was and still is considered the most significant improvement to tube amplifier technology since the 1960s. Even out of production, Berning’s ZOTL amplifiers regularly collect accolades from the world’s top audio reviewers and publications. His ZH-230 amplifier has received Absolute Sound Magazine’s "Editor’s Choice Award" every year since 2011. His Quadrature Z amplifier won HiFi+ magazine’s "Product of the Year" award in 2009. His 211/845 ZOTL amplifier was introduced by Hi Fi One at the 2014 Munich High End Audio Show. Timeless examples of Berning’s audio genius, the ZH-270 and EA-2101 are still highly sought after by audiophiles everywhere.
David Berning plays an integral role in the development of LTA’s offerings. Currently these include LTA's reconfiguration of his original microZOTL personal headphone amp, the ZOTL10, a mid-to-high efficiency power amp, and the ZOTL40, David's latest ZOTL amplifier designed for LTA, which is in essence the successor to his own, much lauded, ZH-230.
Audio amplifier design engineers have long sought to eliminate audio output transformers because of the restrictions they impose on amp performance. Leakage inductance and interwinding capacitance limit the high-frequency response of transformers while core saturation and magnetizing current limit their low-frequency response. Transformer-core hysteresis causes specific distortions of non-symmetric and transient waveforms that are characteristic of musical reproduction. Audio output transformers simply cannot achieve the correct turns ratios as they only max out at 25:1 due to saturation and hysteresis effects. This leaves much to be desired, which creates and issue that needs to be resolved.
Enter the solution: ZOTL.
First, the audio signals “ride” a carrier frequency, on which they are amplified by the tubes (it is not a hybrid amplification design), then the carrier is removed by the Impedance Converters and the remaining audio is delivered to the speaker, similar to how a radio station and receiver work. This changes the impedance plane to match the impedance of the speaker, so the audio output transformer is no longer required to match the tube to the speaker. An Impedance Converter accomplishes this match up. This super linear amplification process allows the amplifier to have a flat frequency response from 8hz to 50Khz, which is nearly impossible with an output transformer.
However, the real advantage is in the transformer turns ratio. Output transformers are limited to a maximum of about 25 to 1 in turns ratio. This turns ratio does the matching between the tube output and the speaker. It turns out that the theoretically correct turns ratio for most tubes is typically 100 to 1 and even as high as 300 to 1. The ZOTL can use the impedance converter to effectively create the ideal turns ratio. The microZOTL has a 300 to 1 ratio and the ZOTL40 has around a 150 to 1 ratio. This results in the detail and accuracy of the sound.
OTL (Output Transformer-Less) amplifiers manufactured by other companies are a completely different technology than ZOTL amplifiers.
ZOTL technology involves a linear amplification process using a carrier frequency as well as not having a traditional audio output transformer, instead using air-core Impedance Converters.
Noted pioneer of amplifier technology, Julius Futterman, has inspired many different amplifier designs over the years. Based on Futterman’s principles, other OTL amplifier designs incorporate two separate banks of parallel-connected tubes. The two banks are joined in series by connecting the effective cathode of one tube bank to the effective plate of the other tube bank, and driving the loudspeaker in a push-pull fashion directly from this junction point without a transformer. There are alternatives to Futterman’s principles that use low-impedance triodes, but the basic principles are the same - given a sufficient number of parallel-connected tubes in each bank, enough drive current can be obtained to drive the speaker.
The output impedance of other OTL amplifiers is nowhere near the actual speaker impedance. In an OTL amplifier, a large amount of negative feedback is required to force the push and the pull to work together properly in order to provide sufficient damping for the speaker. Even with the lowest impedance triodes available, there is still a basic impedance mismatch between the tubes and the speaker in the OTL circuit.
Traditional OTL technology requires a large number of power tubes which need to be driven hard to obtain the required output. This results in drastically reduced reliability and tube life and generating lots of heat. Fans or additional room air-conditioning may be required. Power consumption is typically very high for OTL amplifiers, often exceeding one kilowatt for a stereo pair.
Drastically improved tube life due to lower current operation
No output transformer intermodulation distortion
No low frequency non-linearity
Distortion by parasitic transformer elements of the audio signal no longer occurs
Improved bass due to flat, linear bass response to below 10hz
Removal of low frequency limit for bass response
Correct transformer turns ratio
Low output impedance for easier speaker matching
Having no load cannot damage amplifier
