Requsite Audio Engineering

818.437.0779 Email Danny "Sage" McKinney

Overview
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L7 The Requisite L7 is a 9-pattern, directly coupled condenser microphone capable of +32dB you balanced output. Inherent to its design, the L7 exhibits critical advantages over traditional microphones.

By placing the capsule, head-amplifier, and preamplifier, in the single body we can reduce the head-amplifier coupling cap by 90% and completely eliminate the step-down output transformer.

At this point of the circuit we connect directly to the grid of the preamplifier 6SN7 tube, avoiding 20+ feet of shielded cable, numerous solder joints and connectors to a step-up input transformer, impedance network, pad and high pass filter of a typical recording chain. The Requisite L7 replaces all that with a single silver-in-oil capacitor.
Alison Krauss / L7 Sample

Listen to Alison Krauss, "All Alone Am I", from her new album Windy City. On this track, Alison's voice was record with her L7 condenser... no preamp, no compression, no equalization, no de-essing.

Details

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Special Features

Audiophile Grade

Audiophile grade components are used throughout the L7. Many parts costing a hundred times (or more) the component cost you'll find in top brand microphones. Each stage is built on solid 1/2" thick Teflon blocks, point–to–point, hardwired using solid-core silver and silver copper wire. 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.
9-Pattern Positions

Omni, Cardioid, figure-of-eight, and six intermediate positions. Capsule polarization is accomplished without capacitor couplings, from capsule to the grid.
Linearity Mode

The L7 provides two modes of operation, "Linearity" mode, and "Inductive" mode. In linearity mode the amount of tube generated harmonics (non-linearity's) is user defined by setting Mode select and adjustment of the continuously variable linearity control.

When linearity is at its full C.C.W. position, signal correcting inverse audio tightly controls tube performance and audio is at its "cleanest" 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

Inductive mode is a proprietary circuit developed to alter and control frequency response and dynamic response. Conceptually, a binary star system bound by gravity is a reasonable analogy, so we call it, "Planetary Inductance Effect", or PIE.

In this case, coils are planets, and controlled inductance is gravity. Each coil influences the other by electromagnetic force super imposed with inverse audio derived from a special tertiary winding. When inductance is set to its full C.C.W. position the sound is big and loose, like a vintage ribbon microphone. Adjusting inductance in a clockwise direction the sound becomes more "Hi-Fi", and dynamics are controlled in a transparent, almost undetectable manner.
Tube Rectification

DC power for the L7 is provided by a single 5AR4/G234. This method was chosen for its musicality, and soft start.
Tube Regulation

The Requisite L7 features all-tube regulation, using a 12DW7 vacuum tube.
Tube Audio Output

The output Driver is a 6SN7 running class A, in push-pull configuration. Audio at input is through two silver-in-oil coupling caps.
Tube Preamplifier

Audio from the head-amplifier is a single silver-in-oil capacitor, to the 6SN7 grid. Originally developed in the 1930's the 6SN7 has remained a favorite of the audiophiles for nearly 90 years.
Tube Head-Amplifier

Here we are using the 6072/12AY7. After building nearly a dozen test fixtures, we found this to be our favorite tube for this position.
Molded & Padded Case

Included with the L7 is a custom lined watertight, airtight, dust proof, chemical resistant and corrosion proof hard case. Made of ultra–high impact structural copolymer making it extremely strong and durable. It comes with a top handle, side handle, retractable extension handle, and strong polyurethane wheels with stainless steel bearings. Padlock protectors provides added strength, an extra security against cutting. Dimensions: 32 x 21 x 13
Includes All Cables

Power supply output to mic power input: 7-Pin 12Ft (model CM12cs-7P)
Mic audio output to Power supply audio input: 6-Pin 12Ft (model L12cs-6P)
Supply audio output to receiver input: 3-Pin unshielded, 25Ft (model L25cs)
Power cable from IEC to mains: 6Ft, telescopic shield (model PC6)
Spare Tube Kit

Molded & padded hardshell case contains 5AR4/G234, 12DW7, 6SN7, 6SN7, 6072/12AY7 spare.
MPS-L7 Power Supply

Power supply for the L7 is the MPS-L7. It contains the rectifier to 5AR4/G234 and 12DW7 shunt regulator tube. Power and audio connections to the L7 are made here, as well as, audio output to recording or other sound devices. 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.
Polarity Reverse

Reverses audio polarity from Pin-2 Hi, Pin-3 Low to Pin-3 Hi, Pin-2 Low.
High Pass Filter

This is a very gentle slope of 6dB oct. @ 60Hz. Made at line level.
Line–Level +32dBu balanced output
Output Level Control

This output level is at the very end of line level circuit. It is the only pot in the audio path.