DIY bass amp projects are a great way to achieve a custom sound and look for your rig. You can save money on equipment by building your own bass amp. You can purchase a ready-to-assemble bass amp kit to build yourself, or you can salvage the parts and put them together. Amp kits are easier, while salvaging is typically cheaper. If you are not particularly experienced, amp kits are a good place to start, as all the components are compatible.
Decide on which type of amp you want for your DIY project. Tube amplifier kits are more expensive and require more maintenance but create a warmer sound. Solid-state, transistor-powered amplifiers are cheaper and require less maintenance but tend to have a harsher sound. However, this tonal distinction is less acute in bass amps than in guitar amps.
Acquire your parts. There are three main components in a bass guitar amp: the speaker, the preamp and the power section. If you are purchasing a DIY bass amp kit, all of the necessary parts will come in one package along with a wiring diagram, instructions and surface-mounted components such as resistors and capacitors. Depending on the kit, the cabinet will either be pre-assembled or pre-cut and ready for assembly.
Prepare the cabinet. A salvaged cabinet will have all of the necessary compartments and struts to screw into. If you have a kit cabinet that is not pre-assembled, glue the sides, bottom and top in place and leave them to dry for three hours. Then nail the corner joints together. Leave the back and front until the end.
Install the preamp, which houses the dials and input jacks. The front panel must be exposed at the front of the amp. It sits on the highest ledge inside the cabinet and lies horizontally. Slide it into place, but don't wire it yet.
Install the power section. The power amp houses the mains input, which must be exposed at the rear. This section sits next to the preamp on the top shelf or below it on a separate shelf. Slide the power section into its space. Install the amp chassis on the second shelf. This houses the circuit board.
Fit the speaker. Screw the speaker into the struts that run horizontally across the inside of the top and bottom panel. Speakers typically have four screw holes that run along the circumference of the front end. This is where you screw it in.
Wire the components together. Solder the input jacks to the input terminal on the preamp. Solder the power section to the chassis according to the schematic, then wire the chassis to the preamp. Solder a wire to the output terminal of the preamp and connect it to the speaker.
Test the amplifier. If you're happy that it is working, screw the back panel on and mount the front grille.
If you are salvaging your parts, it's smart to go for a large cabinet to accommodate any upgrades. It also affords you extra room to work with when wiring and soldering.
Make sure the speaker is securely screwed in. A loose speaker will create an unpleasant flapping sound when you play your bass.