Coil Audio CA-70 PS6 Modular Preamp

CA-70 MODULAR MIC/LINE AMPLIFIER

The Coil Audio CA-70 preamp module pays homage to the classic American two-stage circuit invented by Western Electric™ in 1913 and manufactured by multiple companies from the 1930s through the 1950s – most notably RCA™, Gates™, and Langevin™. This old octal tube circuit has a huge thick tone and is what many consider to be the quintessential “old tube preamp” sound.

The CA-70 PS6 preamp module uses our own Coil Audio transformers, high-quality capacitors, resistors, and NOS octal tubes. It’s powered by our PS6 Rack Tray and Power Supply.

The (INPUT) pad section contains a phase reverse switch and a 6 position pad network. The first four positions are various 150/250 ohm mic pads; -6db, -12db, and -19db. The final two (LN 1 & LN 2) positions allow line-level signals to run through the amplifier providing tone-shaping capabilities while mixing from your DAW, Tape Machine, or other Line Level Devices – including other Preamps.

The (NF) control varies the amount of Negative Feedback present in the circuit. Counter-clockwise brightens and moves the sound forward while raising harmonics and sensitivity. Turning it clockwise increases negative feedback, producing a darker tone with a smooth, dampened harmonic structure.

The (HI) switch transitions from the natural openness of the tubes to gentle filtering of upper frequencies. The (LOW) switch reacts with the NF, boosting or cutting low frequency while moving the low end from front to back in the sound stage.

The OUTPUT control knob is placed between the 1st stage 6J7 and 2nd stage 6C5 tubes and sets the final level Output level.

PS6 RACK TRAY & POWER SUPPLY (Sold Separately)

The PS6 Rack Tray and Power Supply can house and power up to six of our CA series modules. It’s comprised of a 7U Rack Tray and a separate 2U power supply. The ‘soft-start’/standby feature allows you to switch the Filament and B+ voltages on and off separately.

TRANSFORMERS (Your Choice of Mic Input Transformer)

• CT-110

Our nickel/iron microphone input transformer based on a punchy 1960s small signal coil. It’s perfect for all-around use and excels at high transient material. The design gives it a very forward, rich mid-range, with smooth saturation in the highs and lows.

• CT-110HN

Our super-mu microphone input transformer based on a rare 1950s hi-fidelity coil. Detail oriented, it adds an excellent top and bottom extension with a smooth, breathy saturation.

• CT-41

Our line output (or input) transformer based on a popular 1960s Peerless design. Frequency response is ruler flat from 20Hz to 30kHz, dipping just below 1db at 60kHz. Its smooth saturation imparts a rich, wooly, hi-fi sound to anything passing through it.

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CA-70 Amplifier:

• Two-stage 6J7/6c5 vacuum tube circuit.
• Negative feedback tone adjustment with high/low filters.
• 42db-54db of available gain.
• Flexible input pad section for mic or line level operation.
• 150 ohm mic, 20k line input, 600 ohm output.
• Interchangeable/optional input and output transformers.
• NOS tubes, signal caps & resistors, PEC 2w carbon pots.
• Up to six CA series amplifiers mount into our PS6 rack.
• Hand built and tested in the USA.

PS6 Rack Tray:

• 7u rack mount chassis.
• Provides housing, audio I/O and power for up to 6 modules.
• Rugged military-grade Cinch Jones connectors.
• Internal point to point wiring.
• Neutrik XLR connections.
• Up to six CA series amplifiers mount into our PS6 rack.
• Hand built and tested in the USA.

PS6 Power Supply:

• Standard 19" 2u rack-mount chassis.
• Filament supply 6.3v @ 4amps, regulated b+/275v supply @ .5amps.
• Switched filament power regulation for 1-3 or 4-6 modules.
• Fault/light indicating fuse holders.
• Internal point to point wiring.
• 5' umbilical power cord with a military Cinch Jones plug.
• Hand built and tested in the USA.