The HC1 is an expandable, high-powered headphone amp designed specifically for critical studio monitoring. The HC1's circuit employs parallel amp stages for greater power and lower distortion. This parallel-opamp concept has been known in theory for decades and was put to practical use in Douglas Self's "5532 OpAmplifier" power amplifier. As a result, the HC1 sounds clean and clear even at high gain and when driving low-impedance headphones. Because everyone's monitoring needs are different, the HC1 is designed to be customized. The power and audio input connectors are screw terminals, so you can attach whichever jacks you need without soldering. You can also daisy chain multiple HC1s to make a multi-channel headphone amp. The HC1 is a great project for intermediate builders who enjoy the challenge of choosing their own chassis and inputs. Features High-current, dual-amp design Screw terminals for power and audio input Stereo, unbalanced audio input Accepts 9v battery or DC wall-wart power input Mounting holes for case mounting Runs about 50 hours on a single 9V battery Does not include power or audio input jacks Partial Kit Includes Printed Circuit Board (PCB) 2x NE5532 opamps All resistors and capacitors required TRS 1/4" headphone jack Volume potentiometer and knob Screw terminals for power and audio input Source Your Own Power supply or batteries Chassis Input jacks Specs Mechanical Size: 2″ x 3.5″ (51 x 89mm) Mounting Holes: 4x #4 (Ø.125", 3.2mm) Full HC1 Mounting Dimensions (PDF) Electrical: Input Impedance: 20kΩ Current Draw: 10-20mA Gain: 0-10dB (customizable) Power Supply: 9 to 44VDC Resources HC1 Assembly Guide HC1 Schematic (PDF) HC1 Bill of Materials (PDF) HC1 Mounting Dimensions (PDF) From the Bench: HC1 Headphone Amp Design (YouTube)
