L7

Common name: Requisite Audio Engineering L7

Production Status: In production

The Requisite Audio Engineering L7 is a multi-pattern, transformer-less, directly coupled condenser microphone capable of +32 dB balanced output. The streamlined circuit is based around a 6SN7 tube, and only uses a single silver-in-oil capacitor. Audiophile grade components are used throughout the L7. Each stage is built on solid 1/2″ thick Teflon blocks, point–to–point, hardwired using solid-core silver and silver copper wire. The capsule polarisation is accomplished without capacitor couplings, from capsule to the grid. All audio caps are silver-in-oil or Teflon. All audio resistors are non-magnetic carbon film. All electrolytic filter caps are multi–bypassed with polypropylene caps. Polar patterns are Omni, Cardioid, figure-of-eight, and six intermediate positions.

The L7 features two operation modes, “Linearity” mode, and “Inductive” mode. In linearity mode the amount of tube generated harmonics is user defined by setting Mode select and adjustment of the continuously variable linearity control. When linearity is at its full counterclockwise position, signal correcting inverse audio tightly controls tube performance and audio is at its most linear setting. Adjusting linearity in the clockwise direction increases harmonic generation as a natural byproduct of vacuum tubes, when allowed to run free of negative feedback. Inductive mode is a proprietary circuit developed to alter and control frequency response and dynamic response. When inductance is set to its full counterclockwise position the sound is big and smooth, like an old ribbon microphone. Adjusting inductance in a clockwise direction the sound becomes more detailed and dynamics are controlled in a transparent, almost undetectable manner.

The DC power for the L7 is provided by a single 5AR4/G234 while the all-tube regulation, is achieved using a 12DW7 vacuum tube. The output Driver is a 6SN7 running class A, in push-pull configuration. The audio input signal goes through two silver-in-oil coupling capacitors. The audio signal from the head-amplifier passes via single silver-in-oil capacitor, to the 6SN7 grid while the tube head-amplifier uses a classic 6072/12AY7.

The microphone includes a custom lined watertight, airtight, dust proof, chemical resistant and corrosion proof hard case made of ultra–high impact structural copolymer. It features a top handle, side handle, retractable extension handle, and strong polyurethane wheels with stainless steel bearings. Padlock protectors provides added strength, an extra security.

Also included are 7-Pin 12Ft (model CM12cs-7P) microphone power to power supply cable, 6-Pin 12Ft (model L12cs-6P) microphone to power supply audio cable, 3-Pin unshielded, 25Ft (model L25cs), Supply audio output to receiver input: 3-Pin unshielded, 25Ft (model L25cs) power supply audio output to receiver input and 6Ft, telescopic shield (model PC6) power cable from IEC to mains.
The microphone case contains 5AR4/GZ34, 12DW7, 6SN7, 6SN7, 6072/12AY7 spare tubes.

The MPS-l7 Power Supply contains the rectifier to 5AR4/G234 and 12DW7 shunt regulator tube. All microphone controls are on the power supply front panel. These include: pattern select, mode select, linearity/inductance control, output level, high pass filter and polarity reverse. Reverses audio polarity is from Pin-2 Hi, Pin-3 Low to Pin-3 Hi, Pin-2 Low. The High Pass filter is 6dB oct. @ 60Hz. The output level control is at the very end of line level circuit and is the only pot in the audio path.