Linear Tube Audio MicroZOTL Preamplifier Level 3 by Terry London

I have almost a decade of reviewing experience with Linear Tube Audio’s creations that are based on David Berning’s very singular ZOTL (Zero Hysteresis Output Transformer-Less) circuit that offers incredible lightning-quick dynamics, absolute transparency / micro-details, and a pristine purity to tonality and colors. My reviews have included the Micro ZOTL 2.0 preamplifier /headphone amplifier, the first generation of the MicroZOTL preamplifier, the Ultra-linear amplifier, and last year’s Aero DAC, which earned a place on the Stereo Times “Most Wanted Components” for 2024. The owner of Linear Tube Audio, which is located in Takoma Park, MD., is Mark Schneider. Mark and David Berning are close friends and collaborated to bring Berning’s ZOTL design to a reasonable price point without sacrificing build quality or performance. The Micro ZOTL preamplifier Level 3 retails for $5,950 with standard tubes. The Level 3 uses two sets of tubes. One set is a pair of either 12AT7s or 12AU7s.

The other set is composed of either 6SN7s or 12SN7s. To switch between the larger 6SN7s/12SN7s, you take off the cover and use an internal switch located by the tube sockets. The chassis of the Level 3 preamplifier is black and is built out of very high-grade aluminum sheets. On the front plate, besides the volume control knob, is a row of control brass buttons that you do not push to engage, but are touch sensitive in use. The Micro ZOTL preamplifier Level 3 is beautiful in its appearance, based on its very high-quality anodized case-work finish and classy brass buttons. The Level 3 preamplifier features an LED readout window, allowing you to monitor the volume level. Another feature that I believe is outstanding regarding the Level 3’s ergonomics is the ability to change the stepped attenuator volume control from 100 steps logarithmic to 199 steps linear, allowing a fine tuning of the volume level. The remote control is well built out of metal and is easy to navigate its functions. The Micro ZOTL preamplifier Level 3 comes with an internal headphone amplifier, which I did not test since I do not use headphones.  The Level 3 preamplifier has 4 RCA inputs and 1 XLR transformer–coupled balanced input. This balanced input uses highly regarded Lundahl transformers.

Linear Tube Audio has made numerous significant changes/upgrades to the Level 3 preamplifier compared to the first-generation Micro ZOTL preamplifier I reviewed and purchased in 2018. For all the details regarding all these changes, I refer you to Linear Tube Audio’s website. However, here are a few of the most salient changes in the Level 3’s design.

1. Uses a single large ceramic circuit board instead of several smaller ones, which vastly shortens the signal path, lowering the noise floor.
2. Significant upgrades in the coupling capacitors. Using the highest grade capacitors from Amtrans and Jupiter Condenser.
3. Increased power supply capacitance by 70% to over 200,00uf.

As I have stated in my other reviews on tube-based preamplifiers, I have a firm position that the first characteristic of a world-class preamplifier is that you do not hear the line-stage; you only hear how the tubes are generating the different aspects of the music. There is no doubt in my mind that the Micro ZOTL preamplifier Level 3 is one of the quietest preamplifiers I have ever had in my system. If I did not know better, based on the Level 3’s nonexistent noise floor, I would believe it was a superlative solid-state design in this parameter. I would attribute this to both the ZOTL design and the Level 3’s superlative power supply.

I decided to use the same musical selections that I had evaluated the first-generation Micro ZOTL preamplifier in my 2018 review. These selections were: 1) John Coltrane’s “Ballads,” which would allow me to get a take on timbres/tonality, top-end air, and decays, and how accurately and percussively the bass frequencies would be reproduced. 2) The album “Rosemary Clooney with Duke Ellington and his Orchestra”. I used this very well-recorded album to get a measure of not only how the Micro ZOTL preamplifier handled sound-staging & placement/location of images on the sound-stage, but the transient speed and dynamic range of Ellington’s orchestra at full tilt. 3) Steve Winwood’s album “Nine Lives” has explosive synthesizer riffs and deep, extended electric bass runs, which allowed me to test for overall macro-dynamics.

The Micro ZOTL preamplifier Level 3 performed at a very high level with the stock tubes they provide. However, when I installed my NOS 1940 TungSol Black glass round plate 6SN7, along with a pair of NOS 1956 CV491/12AU7 Long Plate Mullards, the level of both sumptuous tonality/colors, spatiality regarding both depth and height of the sound-stage, along with air/space between individual instruments, and overall liquidity increased remarkably in my system. In my opinion, all the Linear Tube Audio preamplifiers and amplifiers retain, because of the lightning speed of the ZOTL circuit, including the Level 3 preamplifier, a sense of “aliveness” which brings an excitement you usually only experience in live music.

The Micro ZOTL preamplifier Level 3 is a highly specialized preamplifier that offers the transient speed, virtually nonexistent noise floor, and bass control/slam of the finest solid-state designs. It adds to the exquisite tonality/colors, three-dimensional/palpability of individual images, along with open and airy sound-staging of the finest tube-based designs. The Level 3 preamplifier offers exceptional improvement over the original generation Micro ZOTL preamplifier. If you are someone who enjoys tube rolling in your system for variety or to match the preamplifier’s performance for synergy, the Micro ZOTL preamplifier Level 3 is a must-try for you.

Specifications:
Price – $5,950
Dimensions – 17 inches wide, 4.2 inches tall, 12.4 inches deep
Weight – 14 pounds
Tube complement – 2 x 12AU7/12AT7 2 x 6SN7/12SN7
Volume control – two settings – 100 steps logarithmic or 199 steps linear
Inputs – 4 RCA’s, 1 XLR transformer – coupled balanced input with Lundahl transformers, one tape input
Outputs – headphone jack – tape monitor output – dual RCA single-ended output
Website: www.Lineartubeaudio.com

Terry’s Associated Equipment
Source: Pass Labs DAC-1
Reimyo DAP-999EX Toku DAC
Mark Levinson 31.5 transport
Pro-Ject reference CD transport & LTA power supply
Wadia 22 transport
CEC t-3 belt-driven transport
Amplification:
Coda 5.5 amplifier
SPL 1200 amplifier
SPL Elector preamplifier
Plinius SA-50 amplifier
Threshold 550e amplifier
Aric Audio Super 300B SET amplifier
Aric Audio Custom 12ax7 balanced preamplifier
Loudspeakers:
Rosso Fiorentino Arno 40
NSMT System Two
Music Design Knight one
Accessories:
Jena Labs Symphony XLR ICs
Jena Labs Reference AES/EBU digital cable
Vermouth Audio Reference speaker wire
Vermouth Audio Black Pearl MKIII XLR ICs
Krolo Design reference rack & footers
Puritan Audio power conditioner & grounding system
Audio Archon power cords