The preamp section of a guitar amplifier turns the low-impedance guitar signal into a high impedance electrical current. The preamp op-amp chip then processes that electrical current and sends it to the power amp. Guitar amps are either integrated units, containing preamp and power amp sections, or stand-alone units. A stand-alone preamp unit is connected externally to a power amp, which is connected to an external speaker cabinet. Stand-alone preamps are typically rack-mounted for ease of operation. You can make your own guitar preamp using a self-assembly guitar preamp kit.
- Skill level:
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Things you need
- Preamp kit
- Soldering iron
- Wire strippers
Select a kit. A variety of online retailers sell self-assembly guitar preamp kits. The Quasar Electronics website lists a relatively simple, battery-powered guitar preamp. The London Power website lists a number of kits, including a two-channel preamp and an "American Style" guitar preamp. Some are more complicated to assemble than others. Read the descriptions and select the one that you feel best suits your skill level.
Inspect the parts. Check the circuit-board-mounted components for damage. If you are building a tube amp, check the tubes for cracks. Damage to new parts can occur in transit.
Load the circuit board. The circuit board is where the guitar signal is processed. Read the schematic for reference and fit each component in its turret. Board-mounted components typically include resistors, capacitors and an op-amp chip. Once the board is completely populated, place it on its front and solder the connectors to the metal rails that run along the base.
Place the potentiometers inside the precut holes in the front of the chassis.
Cut a 3-inch piece of wire for each potentiometer. Strip each end to expose the metal.
Solder one end to the top terminal on the potentiometer and solder the other end to the correct eyelet on the board. The potentiometers control the flow of current across the board, depending on the position of the dial. Attach the dials to the front of each potentiometer. Ensure that zero is level with the notch in the potentiometer pole.
Connect the IEC power supply or battery snap. In either case, solder the red wire to the positive eyelet and the black wire to the ground eyelet.
Solder the input jack to the first op-amp chip. Solder the output jack to the second op-amp chip.
Screw on the top and back of the chassis to enclose the preamp.
Tips and warnings
- Colour code the components with their turrets on the board with a coloured marker pen.
- Solder only in well-ventilated spaces.
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