Mystery Magicians M808A Single-Channel Valve Microphone Preamp

The M808A is a sophisticated channel strip 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 lossless tube filters offer four useful HPF and LPF frequencies with -6dB per octave (-20dB per decade) attenuation for quick program material decisions. The Line In feature places signals before the gain control into the 6350 tube and signal chain, ideal for keyboards, drum machines, and mix bus insertion with sonic coloration and makeup gain. Fully regulated SMPS power supply with auto-detectable line voltage (86VAC – 265VAC) provides extreme reliability, high ripple rejection, low noise floor, and short-circuit protection for global operation.

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, 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 Lossless Tube Filters: Four useful HPF and LPF frequencies with -6dB per octave (-20dB per decade) attenuation enable quick program material shaping decisions.
• Versatile Line Input Insertion: Line In places signals before the gain control into the 6350 tube and rest of the signal chain, ideal for keyboards, drum machines, and mix bus insertion with sonic coloration and makeup gain.
• Wide Input Compatibility: Accepts condenser, dynamic, and ribbon microphones (33Ω – 600Ω output impedance) plus bass, electric guitars, keyboards, organs, drum machines, and line-level sources with excellent results.
• Fully Regulated SMPS Power Supply: Auto-detectable line voltage (86VAC – 265VAC) with fully regulated internal voltage nodes provides extreme reliability, high ripple rejection, low noise floor, and short-circuit protection for global operation.

Specifications

• Type: Single-channel valve microphone/instrument/line preamp
• Circuit Design: Class A single-ended with transformer-coupled I/O
• Tube Complement: 6350 output tube, EF86 mic input tube
• 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)
• Filters: HPF and LPF with -6dB per octave (-20dB per decade) attenuation, active lossless tube design
• Front-End Attenuation: -10dB / -20dB
• VU Meter: Custom bakelite with traditional ballistics, selectable +4dBu or +8dBu range
• Phantom Power: +48V with anti-pop soft start/stop switching and indicator
• 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
• Power Requirements: 86VAC – 265VAC, 50 – 60Hz (auto-detectable line voltage)
• Power Supply: Fully regulated SMPS with short-circuit protection on all voltage nodes
• Optional Accessory: M808APB patchbay for all I/Os on front panel
• Recommended Applications: Tracking, recording, DI for instruments, sound design, saturation, mix bus processing, keyboards, drum machines