Wiring diagram for Ampin Jean Hiraga class A amplifier kit
This wiring guide is designed for the Jean Hiraga Class A Amplifier Kit. Whether you are planning your build or have the components on your bench, following this layout is essential for achieving the ultra-low noise floor this legendary circuit is known for.
Installation & Wiring Instructions
Building a Class A amplifier requires strict attention to "lead dress" (wire routing) and grounding. Use the following steps to complete your assembly.
1. AC Mains & Soft Start
Safety First: Connect the AC mains through the Power Switch and then to the Inrush Limiter (Soft Start) board. This protects your bridge rectifier and household breakers from the massive current surge required to charge the capacitor bank.
Safety Earth: Connect the ground wire from the mains plug directly to a dedicated bolt on the metal chassis.
2. The Power Supply (PSU)
Rectification: Connect the 22V-0-22V AC leads from the transformer to the AC terminals of the bridge rectifier.
Star Grounding: The Center Tap (0V) of the transformer must go directly to the main Ground (GND) bus on the capacitor board.
Thermal Note: Bolt the bridge rectifier to the chassis or a dedicated heat sink using thermal paste; it will generate significant heat during operation.
3. Noise Management (Ground Loop Breaker)
To eliminate speaker hum, wire the Ground Loop Breaker (the resistor/capacitor/diode parallel network) between the Circuit Ground and the Chassis Earth.
This ensures the amplifier is safely grounded while breaking the loop that causes 50Hz/60Hz interference.
4. Module Connections
DC Rails: Run +V, -V, and GND wires from the PSU board to each amplifier module. Twist these wires together to minimize electromagnetic radiation.
Input Signal: Use high-quality Shielded Coaxial Cable for the RCA inputs. Keep these as far as possible from the transformer and AC wiring.
Speaker Outputs: Connect the Red (+) post to the PCB "SPK OUT" and the Black (-) post to the PSU "GND" terminal.
Pre-Power Checklist
Transistor Isolation: Ensure all power transistors are electrically isolated from the heatsink using mica or silicone pads (unless the heatsink is intended to be live).
Thermal Sink: NEVER power up the modules without a substantial heatsink attached. Class A transistors reach operating temperature almost instantly.
Transistor Isolation: Ensure all power transistors are electrically isolated from the heatsink using mica or silicone pads (unless the heatsink is intended to be live).
Thermal Sink: NEVER power up the modules without a substantial heatsink attached. Class A transistors reach operating temperature almost instantly.
Purchase the Kit
Ready to build your own? You can find the complete PCB sets, matched transistor kits, and specialized power supply components at the link below:
Ready to build your own? You can find the complete PCB sets, matched transistor kits, and specialized power supply components at the link below:
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