Coil Audio CA-70S — Single-Channel Tube Microphone Preamplifier

The Coil Audio CA-70S is a standalone, single-channel 2U tube preamplifier built around the same American-style circuit, transformers, and high-end components found in the CA-70 PS6 preamp module—with onboard power and a streamlined control layout. The heart of the CA-70S is a two-stage, single-ended 6J7/6C5 vacuum tube circuit, delivering the thick, weighty character that defines classic Octal tube preamp tone. CT-110HN high-nickel input and CT-41 output transformers anchor the signal path alongside NOS tubes, PEC carbon pots, and selected signal caps and resistors. The CA-70S is hand-built and tested in the USA.

Key Features

• Two-stage single-ended 6J7/6C5 vacuum tube circuit with 42dB–54dB of available gain
• CT-110HN high-nickel input transformer and CT-41 output transformer
• Negative feedback tone adjustment with LOW filter
• Flexible input pad section for mic or line level operation (150Ω mic input, 20kΩ line input, 600Ω output)
• NOS tubes, signal caps and resistors, PEC 2W carbon pots throughout
• Slow-ramping, linear-regulated power supply to prolong tube life
• 2U all-steel enclosure with integrated power supply
• Hand-built and tested in the USA

Specifications

• Form Factor: 2U rackmount
• Channels: 1
• Tubes: 6J7/6C5 (NOS), single-ended circuit
• Input Transformer: CT-110HN high-nickel
• Output Transformer: CT-41
• Gain Range: 42dB–54dB
• Mic Input Impedance: 150Ω
• Line Input Impedance: 20kΩ
• Output Impedance: 600Ω
• Power Supply: Integrated, slow-ramping linear regulated
• Construction: Hand-built and tested in the USA