Coil Audio CA-70 Modular Mic-Line Amplifier

  • $1,749.00

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The 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 custom Coil Audio transformers, high quality capacitors, resistors, and NOS octal tubes. It's powered by the PS6 Rack Tray and Power Supply (sold separately).

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 allows 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 a 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.


  • Two-stage 6J7/6C5 vacuum tube circuit
  • Negative Feedback (NF) tone adjustment
  • High and Low filters
  • 42-54dB of variable gain
  • Flexible input pad section for MIC or LINE level operation
  • Input impedances - 150 ohm (MIC), 20k ohm (LINE)
  • Output impedance - 600 ohm
  • Interchangeable (optional) input and output transformers
  • NOS tubes, signal caps & resistors, PEC 2w carbon pots
  • Hand built and tested in the USA
  • Important!  CA-70 modules require a PS6 power supply for operation

Note:  The CA-70 modules ship directly from Coil Audio.  Please contact us for estimated delivery times.

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