There are two types of amplifier output circuit: Push-pull output circuits that are wired so that the output current is split and runs in parallel and single-ended output stages that are not split and run in a linear fashion. Single-ended amplifiers can generate more power from less current. Single-ended tube output circuits are used in both audio and instrument amplification. There is less distortion in a single-ended amplifier because the output currents do not cross over. You can construct your own single-ended tube audio amplifier with a self-assembly kit.
- Skill level:
Things you need
- Single-ended amplifier kit
- Schematic (comes with kit)
- Magnifying lens
- Soldering iron
- Latex gloves
Acquire the parts. Select a single-ended tube audio amplifier kit that best suits your needs. If you already own speakers, check their maximum power rating, which will influence your amplifier selection.
Inspect the parts with a magnifying lens to check for damage, such as cracks on the tube and oxidisation on the resistors and cathodes.
Open and study the schematic, which illustrates the layout and nature of the circuit. Use a coloured marker pen to colour code each component with its symbol on the schematic. This makes populating the circuit board easier.
Load the circuit board. Kits come with a blank printed circuit board that have pre-drilled turrets. Fit each board-mounted component into its turret, according to the schematic. Push each part into the turret so that the connectors protrude through to the other side. The amount and type of board-mounted components varies from kit to kit, but typically there are resistors, diodes, tube bases, an IEC power supply and op-amp circuit chips.
Wire the circuit board. Carefully place the board face down once all of the components are loaded. Use a soldering iron to fit the connectors to the metal strips that run along the base of the board. These metal strips connect each individual component.
Assemble the chassis, which forms the housing of the amplifier. The transformers, potentiometers and tubes are chassis-mounted. Load the power transformer in the largest square hole. Ensure the solder lugs are level. The location of this hole depends on the model of the amplifier. For example, the power transformer on the 6T9 amp is centrally located on top of the chassis. Install the output transformers in their pre-drilled holes and ensure the solder lugs are level. Fit the potentiometers into the pre-drilled circular holes on the front of the chassis. Wire the transformers to the tube bases according to the schematic.
Load the circuit board. Wire it in to the base of the chassis. Fit the IEC power supply to the chassis, and wire it to the board. Connect the red wire to the positive eyelet and the black wire to the negative. Solder a wire to the output terminal of each potentiometer. Connect that wire to the relevant eyelet on the printed circuit board.
Load the tubes. The tubes slot vertically into the tube base.
Tips and warnings
- Practice soldering on scrap wire and metal before beginning. Solder drip can create diversions in your circuit.
- Use caution when dealing with high-output electrical devices. Consult a qualified electrician, if necessary.
- Wear latex gloves to protect the tube glass from skin oils.
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