Disclaimer: the MZ2-S I borrowed from Linear Tube Audio in order to finish a Headfonia review of it, as well as follow-up reviews/comparisons both there and here. Without the power supply, it goes for 1845$ USD. You can find out all about it here: Linear Tube Audio MZ2-S.
Update: the original version of this article suggested that I matched the MZ2-S's output to that of the Astell&Kern AK380. It should have read: iPhone 6. I have since amended the error.
The Linear Tube Audio MZ2-S, which I originally mistook for the microZOTL2,0, is a brilliant in/out valve amp whose design/performance niggles are minimal. According to Linear Tube Audio, its biggest design niggles: depressed power button, and attenuator noise, have been fixed. I can neither confirm nor deny this.
What I can say is that this amp delivers good current to most headphones out there. And, despite being limited to 1W output, its power amp section gives a good punch to low-Ω impedance speakers. In my case, the speakers are Acoustic Energy’s Aegis Model 2, a floor-stander, which, through the Centrance PX, is all mids and highs. Through the MZ2-S, those speakers have balls… bass balls. And the same goes for headphones. Great bass, somewhat more stereo crosstalk than the mids and highs, but brilliant.
Its frequency response is nearly ruler-flat, and loaded, extended. It is as detailed. It is powerful. It is just tubey enough to satisfy valve lovers, but not tubey enough to put off solid state lovers. And still, it’s more tubey than a hybrid. Brilliant. Brilliant.
Relevant RMAA measurements:
RMAA: ALO Audio CDM (Continental Dual Mono) 16-bit & 24-bit loaded/unloaded
RMAA: Cypher Labs AlgoRhythm Trio 24-bit — ohm image
RMAA: Phatlab Audio PHAntasy 24-bit
RMAA: Chord Mojo 24-bit
RMAA: Lynx Studio HILO
NL - no load
SM2 - Earsonics SM2
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880/600
24-bit summary +6dB (volume matched to the AK380 maximum).
Niggles are few, features abound, performance is many. This is a great amp.