I have had the MZ2 that I modified with wiring, etc., but the topology is the same as stock. The MZ3 has some real changes and I love the looks of the case. This should be a very worthwhile listen. Remember the 12SN7 is a bargain of a tube and quieter than it identical, though lower filament voltage, 6SN7. Good Stuff! The MZ3 also uses a ceramic board! Can't get much better than that. User Manual. Here https://www.lineartubeaudio.com Information copied from Linear Tube Audio's web page: The microZOTL MZ3 represents the evolution of the microZOTL technology as a headphone amplifier, a preamplifier, and a 1 watt speaker amplifier in the external power supply form factor of the MZ2. Incorporating almost all of the technology enhancements recently released in our new microZOTL Preamplifier, the microZOTL MZ3 is the result of years of refining the microZOTL circuitry. This is the highest expression of the amp as a preamp, headphone amp, and 1 watt speaker amp. In a beautiful new, low-resonance aluminum chassis designed by Fern & Roby, the microZOTL MZ3 contains all of the elements that we found improved the sound significantly. A digital interface features an LED array display for volume and input, a new remote-controlled stepped attenuator volume control, and improved input wiring that greatly shortens the signal path. The power supply is larger and more refined, with a premium interconnect cable, and no more turn on thumps. There are several integral component upgrades in the audio circuit for wider soundstage, lower noise floor, and improved musicality. We now use ceramic circuit boards for the amplifier, which result in the clearest, cleanest sounding microZOTL yet. We curate premium tubes for you to ensure you experience the amplifiers’ maximum performance right out of the box. SPECIFICATIONS Inputs: 3 Stereo single ended RCA high quality connectors using sealed, silver contact relay control for a short signal path Outputs: Headphone ¼” Phone jack, Dual preamp RCA outputs single ended, Stereo speaker binding posts Amplifier class: Push-pull Class A, no feedback Sensitivity: 0.6V RMS [full output] Output impedance: (measured @ 0.5A, 60 Hz) 2 ohms for headphone and speaker outputs, 50 ohms for preamplifier outputs Input impedance: 50k Volume Control: Stepped attenuator constructed of 1025 steps of 50 ohms, with 100 positions selected to provide very fine resolution at the lowest volumes and a logarithmic control for higher volumes . Low noise, precision 1% Vishay Dale resistors and hermetically sealed silver contact relays are used for precise, isolated analog signal attenuation Balance Control: 100% channel isolation using stored differences of volume values. Maximum balance differential is 16 steps Power Supply: Linear supply user-switchable between 110/120 and 220/240 (100V linear supply available for Japan). Uses dual banks of organic poly ultra low ESR capacitors (4 times MZ2) for over 100KuF of output choke isolated storage. Oversize transformer secured with aluminum and brass mountings (no steel). Regulation is performed using low noise Belleson super regulators. Current transformer controls output protection circuit Power Supply Output: 12VDC 3 amps Power Supply Umbilical Cable: premium low noise shielded cable with silver contact, spring loaded premium XLR connectors Hum and noise: minimum 60mV RMS or 90dB below full output (20Hz-20kHz) Power consumption from ac power source: approx. 50W Power output: with 4-ohm load: 1W, 1% THD, with 14-ohm load: 0.5W, 1% THD Channel separation: (4-ohm loads) 46dB, 100Hz-10kHz, (14-ohm loads): 54 dB, 100Hz-10kHz Frequency response full power: (4-ohm load) +0, -1dB 10Hz-20kHz, (14-ohm load): +0, -1dB 5Hz-50kHz, Voltage gain: (4-ohm load): 10.3dB, (14-ohm load): 12.4dB Front Panel Control: Functions include volume, input select, headphone/speaker output select, and amplifier power on-off. Remote Control: All functions, including Mute and the configuration menu, are available from the remote, except power on-off and headphone/speaker output selection. Uses an Apple TV remote. The remote is registered to unit to limit control from unintended remotes. The Right-Left buttons can be configured as balance controls. Auto-save Features: Volume level per input is automatically saved and the unit powers on using the stored volume levels. Balance and all other configuration menu selections are all saved as a global level across all inputs. Display Controls: 16 levels of brightness and on-off selectable 7 second timeout Home Theater Mode: an input can be selected from configuration menu to set one of the inputs to a high volume level fixed input to allow surround sound device control the volume level Size: amp: 9 1/2 inches (24.1 cm)wide, 4 3/4 inches (12.0 cm) tall, 7 7/8 inches (19.7 cm) deep (including connectors) Linear Power Supply: 12" (30.48 cm) x 3.25" (8.26 cm) x 4.25" (10.8 cm) Net weight: with switching supply: 5.35 lbs (2.5 kg) - amplifier and external power supply) with linear supply: 8.94 lbs (4.1 kg) - amplifier and external power supply) Tube complement: 2 premium hand selected 12AT7 input tubes, and two premium hand selected 12SN7 output tubes. (6SN7s can be used with jumper settings) 12AU7s are often substituted for the 12AT7s to lower the gain if higher headphone output is not required.