Linear Tube Audio MicroZOTL MZ2 Review

Many of you will likely have heard passing reference to the MicroZOTL from a few years back when a number of hand-made semi-DIY kits got some buzz in the community.

Those units as I recall were fairly crude chassis, and had a somewhat thick, uncontrolled bass, but there was something incredible about the clarity and resolution of the midrange and treble that meant they were hard to come by. Once purchased, they were rarely let go of. In the ensuing years Linear Tube Audio has grown a bit from a one-man shop replicating the designs of David Berning, to a full-fledge company with multiple employees, a shop, and the engineering know-how to tweak David Berning’s base MicroZOTL topology into something very special.

I spoke with Mark, the man behind LTA and the old DIY MicroZOTL amps and he gave me a very informative rundown on the history of the company. Essentially he began licensing the MicroZOTL and switching power supply topologies of David Berning and building the amplifiers some years ago, and the demand was so high that he’s since built up a small outfit and partnered with Fern & Roby to make much nicer cases for the gear. He also has enough engineering talent onboard that the David Berning designs now get additional tweaks – separate power supplies, higher quality parts, and tweaks to various operating parameters that all go back and get approved by Berning himself.

The result has been many small sonic improvements since the early units that have added up. At AXPONA this past year I stopped briefly by the LTA table and was mightily impressed by what I was hearing. I asked for a review sample and here we are.

The unit I chose is the MZ2, the least expensive headamp the company makes, though it can also serve as a preamp and even a one-watt speaker amp in a pinch. There are a multitude of options between a remote control, NOS tube options, and different lengths of cable between the outboard power supply and main unit. The base unit price without any fancy upgrades is $1,235 USD, in comparable territory to the Feliks Elise and several other very competitive tube amp/preamp options. In my experience the choosy enthusiast can find some of the most competitive, high-value-per-dollar gear in this price range, and it’s a price point where the expense of proper power supplies and decent tubes and capacitors become a possibility.

We’ll see how that plays out with regard to the MZ2.

Build quality and design

The unit itself is modestly sized, though not small, even with the long, narrow power supply included. The box the entire package came in was massive and about 60 per cent foam packing material, so I suspect the number of these that get damaged in shipping is pretty small. The unit I received came with the optional remote control, the standard New-Production 12SN7 tubes and standard 2M power supply DC cable. The casework on these new units is nothing like the old units – the front plate alone on the MZ2 I received is more metal than most headphone amps I’m used to. It’s quite plain, but the smooth matte black surface with simple white engraving is really sleek. There are some red lights that illuminate the area underneath the unit as well, giving it an aggressive need-for-speed type appearance. Understated, but definitely high quality.

The crowning piece is the industrially thick glass plate on top allowing you to see the board inside. Wiring is superbly clean and high quality, and the parts do indeed seem to be very high quality and carefully selected. The design topology of the amp is quite interesting, according to LTA the ZOTL design runs tubes at twice the voltage and one-third the heater plate current, without any of the ill effects typically associated with such use. The results should be a more linear operation of the tube, with less frequency variation, and importantly, at a very low output impedance, which means the amp does not require output transformers or other coupling tricks to bring impedance to usable levels.

The MZ2 I have in for review is specified as having a two-ohm output, which means, like a solid-state amp, it should work with just about any headphone. LTA has also switched from a 6SN7 tube to a 12SN7, which is functionally the same, but runs at a higher voltage than the 6SN7. Apparently the decision was made in order to keep costs down and in the pursuit of untouched NOS tube stocks, as the recent popularity of the 6SN7 has driven up prices. It’s clear from speaking with the folks at LTA they’re quite conscious of balancing the price and performance of the MZ2 to keep it at a more reasonable point than their higher-priced gear. Let’s take a listen and see if it’s paid off.

Linear Tube Audio

Simply Nobody's picture

May be inner/Fidelity could also review the new Manley Absolute tube headphone amp? :-) ........

Grover Neville's picture

I’ve actually got it right here and am in the process of reviewing it!