Mystery Magicians M808A Dual-Channel Valve Microphone Preamp

The M808A is a sophisticated dual-channel strip-style tube preamp designed for faithful amplification and reproduction with rich, clean sonic output. This Class A single-ended design delivers up to 80dB of gain through custom hand-wound input and output transformers hermetically potted in MuMetal casings, producing sonic characteristics compared to British tube consoles of the 1960s despite being designed from the ground up without following traditional schematics. Switchable Pentode/Triode mode operation provides variable gain and unique harmonic colorations, while a state-of-the-art saturation detector circuit monitors total harmonic distortion of the mic input tube with front-panel pilot light indication for verifying clean headroom before tube saturation occurs. The channel strip configuration handles mic, line, and DI inputs with transformer-balanced insert points for integrating vintage tape echoes, reverbs, equalizers, compressors, and effect pedals. Active true-bypassable filters offer four useful HPF and LPF frequencies (50Hz, 150Hz, 2kHz, 5kHz at -6dB per octave Butterworth first-order) for quick program material decisions. Premium NOS 6350 output tubes matched to 1% ensure perfect gain tracking between channels, while the fully regulated solid-state power supply with soft start and short-circuit protection operates globally from 86VAC to 260VAC. Custom bakelite VU meters with traditional ballistics, GR-style bakelite knobs from original molds, Switchcraft and Neutrik connectors, Japanese TOCOS sealed potentiometers, and 4mm carbon steel faceplates complete the premium construction.

Key Features:

• Class A Single-Ended Design with Hand-Wound Transformers: Custom input and output transformers designed and wound in-house, individually tested and hermetically potted in MuMetal shielding for sonic character compared to 1960s British tube consoles.
• Switchable Pentode/Triode Operation: Pentode mode delivers 80dB maximum gain (10Hz – 25kHz ±1dB), Triode mode provides 70dB with different harmonic characteristics for tonal flexibility and creative saturation options.
• Saturation THD Indicator: State-of-the-art detection circuit monitors mic input tube total harmonic distortion with front-panel pilot light, allowing engineers to verify clean headroom on the fly before saturation occurs.
• Transformer-Balanced Channel Strip Configuration: Mic, line, and DI inputs with transformer-balanced insert points accommodate balanced and unbalanced effects (vintage tape echoes, reverbs, EQs, compressors, pedals) with balanced LINE OUT signal.
• Active True-Bypassable Filter Section: Four lossless tube filter frequencies (50Hz, 150Hz HPF / 2kHz, 5kHz LPF) at -6dB per octave (Butterworth first-order) enable quick program material shaping decisions.
• Premium NOS Tubes with 1% Matching: 6350 output tubes matched to 1% tolerance ensure perfect gain tracking between channels, while New Old Stock valves are individually selected for each manufactured unit.
• Custom Bakelite VU Meters and Hardware: Designed and manufactured with traditional ballistics, paired with GR-style bakelite knobs from original molds for authentic vintage aesthetic and tactile response.
• Fully Regulated Power Supply: Solid-state switching design with soft start, short-circuit protection, automatic line voltage recognition (86VAC – 260VAC), high ripple rejection, and low noise floor for global operation and extreme reliability.

Specifications

• Type: Dual-channel valve microphone/instrument/line preamp
• Circuit Design: Class A single-ended with transformer-coupled I/O
• Tube Complement: Premium NOS 6350 output tubes (1% matched), EF86 mic input tubes
• Mic Input Impedance: 2kΩ (accepts 33Ω – 600Ω microphones)
• Maximum Gain (Pentode): Approximately 80dB
• Maximum Gain (Triode): Approximately 70dB
• Frequency Response (Pentode): 10Hz – 25kHz (±1dB @ 100Ω source impedance)
• Frequency Response (Triode): 10Hz – 25kHz (±1dB @ 100Ω source impedance)
• DI/Instrument Input Impedance: 1MΩ
• Line Output Impedance: 600Ω or 150Ω @ +4dBu output
• Insert Send Impedance: 250Ω
• Insert Return Impedance: 100kΩ
• Maximum Output Level: +10dBu @ 1% THD
• THD+N @ +4dBu: 0.02% (second harmonic dominant)
• Signal-to-Noise Ratio: >85dB (A-weighted)
• Crosstalk: -100dB between channels
• Filters: HPF (50Hz, 150Hz), LPF (2kHz, 5kHz) @ -6dB per octave (Butterworth first-order), active true-bypassable
• Front-End Attenuation: -10dB / -20dB
• VU Meters: Custom bakelite with traditional ballistics, selectable +4dBu or +8dBu range
• Phantom Power: +48V with individual anti-pop soft start/stop switching and indicator per channel
• Transformers: Custom hand-wound input and output, hermetically potted in MuMetal casing
• Components: Metal film resistors, foil and film capacitors, Rubycon and Nippon Chemi-Con electrolytics, all through-hole (no SMDs)
• Potentiometers: Japanese TOCOS sealed
• Connectors: Switchcraft and Neutrik
• Switches: Carling toggle, high-quality sealed Japanese relays with gold contacts
• Knobs: Custom GR-style bakelite from original molds
• Faceplate: 4mm carbon steel
• Construction: Modular design throughout
• Power Requirements: 86VAC – 260VAC, 50 – 60Hz (automatic line voltage recognition)
• Power Supply: Fully regulated solid-state with soft start and short-circuit protection
• Optional Accessory: M808APB patchbay for all I/Os on front panel
• Recommended Applications: Tracking, recording, DI for instruments, sound design, saturation, mix bus processing