For someone who doesn’t listen much to headphones, I happen to have a fair number of them on hand. My favorite in the circumaural category are the Sennheiser HD 600 cans, mainly because of their excellent tonal balance and smooth presentation. The microZOTL2.0 pushed the HD 600 to a performance level I had not previously experienced. Prior to the microZOTL2.0 I had used the HD 600 extensively with the Antique Sound Lab MG-Head OTL 32 DT headphone amplifier. This is an all-tube OTL design, which uses a pair of triode-connected 6BQ5/EL84 pentodes per channel in the output stage. The sonic result could best be characterized as being overly tube-like: a nice fat lower midrange combined with a noticeable loss of transient speed. In other words, the HD 600 was easy to listen to but lacking in clarity and detail resolution—simply put, its presentation was “decaffeinated.” In this context, there was no way anyone would mistake these cans for a high-resolution device, let alone reach a sonic orgasm. Adding the microZOTL2.0 to the chain transformed the HD 600—almost as if it had received a shot of caffeine. The HD 600 sounded faster and much higher in resolution. For example, I was now able to clearly distinguish between different upsampling settings on the Eximus DP1 DAC.
Sonically, the best headphones in my collection are the Stax SR-X Mk2, which I use with the SRD7 Pro interface. These decades-old cans run circles around the HD 600. I keep them around for the same reason I hang on to my Quad 57 ESLs—a gorgeous midrange, absolutely to die for. Good electrostatic speaker designs seem destined to become classics for the simple reason that they leave little room for improvement. With the SRD7 connected to the microZOTL2.0’s speaker terminals, the Stax projected incredibly suave mids saturated with microdynamic subtlety. And there was nothing wrong with the treble range, which was reproduced with exceptional extension and air, and without any electronic artifacts. Together, these components forged a natural and synergetic partnership.
Most of you are probably familiar with Chesky’s binaural demo album titled Dr. Chesky’s Sensational, Fantastic, and Simply Amazing Binaural Sound Show. It contains a lot of good music as well as some neat test tracks. I agree with Chesky that binaural (aka dummy head) recording, far from being a gimmick, is an important technique for capturing the sensation of being there, in essence providing a live concert perspective. The right and left channel ID tracks have David Chesky initially standing some 30 feet from the mike in a reverberant cathedral acoustic. He talks as he walks closer and closer and ends up whispering in your ear. That’s a pretty impressive demo of the imaging capability of a good binaural recording. Getting a feel for the acoustic space of the recording was effortless with the microZOTL2.0 in the chain.
The microZOTL2.0 is one of the few headphone amplifiers that can truly deliver an emotionally charged listening experience. Since the microZOTL2.0 is sold direct to the public, without the usual dealer markup, it represents an uncommonly good deal. But it’s more than simply a question of money. Here, for the first time, via ZOTL technology, it is possible to experience the magic of a 6SN7 “power” tube. This may sound like a TV commercial, but the new and improved microZOTL outshines the original. That should not come as a surprise given the use of enhanced passive parts and better tubes. To my mind, the microZOTL2.0 is the pinnacle of desirability when it comes to headphone amplifiers.
SPECS & PRICING
Frequency response (full power): 10Hz–20kHz +0/-1dB (4-ohm load); 5Hz–50kHz +0/-1dB (14-ohm load)
Power output: 1W into 4 ohms (1% THD); 0.5W into 14 ohms (1% THD)
Sensitivity: 0.6V RMS
Output impedance: 2 ohms (0.5A/60Hz)
Input impedance: 50k ohms
Hum and noise: 90dB below full output (20Hz–20kHz)
Voltage gain: 10.3dB (4-ohm load); 12.4dB (14-ohm load)
Dimensions: 9.5" x 4.75" x 7.875"
Net Weight: 5.35 lbs.
LINEAR TUBE AUDIO/URBAN HI-FI
Analysis Audio Omega loudspeaker; VTL Manley reference series 100/200 monoblock amplifier; AVA Vision phonostage; Kuzma Stabi Reference, Technics SL-10, Revox B795, and Sony PS-X600 turntables; MacBook Pro laptop running Amarra V3.03 software, April Music Eximus DP1 DAC; ModWright modified Sony XA-5400ES SACD player: FMS Nexus-2, WireWorld, and Kimber KCAG interconnects; Kimber KCAG speaker cable; Monarchy Audio AC-Regenerator; Sound Application power line conditioners