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DIY Amplifier — Build a Great Sounding Audio Amplifier At Home

DIY Amplifier

In layman’s terms, an amplifier is one that takes a signal and makes it louder. You just need to connect the amplifier to the speaker to be audible loud enough to be heard. And in this world of DIY’s the amplifier is not behind. You can make a DIY amplifier with components that are easily available.

Below is a tutorial on how you can make a DIY amplifier:

Materials

  • 1 toroid transformer with double secondary windings: at least 120 VA max output, 2x 12-18 Volt. I
  • 2x 10,000 uF / 35 V electrolytic capacitors
  • 1x rectifier module KBU1005
  • 1x Anti-interference filter for mains supply.
  • 1x switch.
  • 1x male power plug, Euro model. These plugs are also sold with an integrated power switch.
  • 1x 3 Amp fuse with socket
  • 1x 10mm red LED
  • 1x 100 kOhm resistor to dim the LED
  • About two meters of heavy duty power cable.

Amplifier:

  • 2x LM3886 op-amps
  • 1x 22kOhm potentiometer, logarithmic scale.
  • Resistors: 2x 2.7 (2 Watt), 2x 680, 2x 1k, 2x 10k, 4x 22k
  • Capacitors electrolytic: 2x 47 uF, 4x 100 uF
  • Capacitors film (MKP type): 4x 0.1 uF
  • Something that can act as a heatsink for the op-amps. Use a piece of aluminum tube (square profile, 30×30 mm)

Connectors:

  • 1 set of RCA “audio-in” connectors.
  • 2 sets of lab connectors to connect the speakers
  • 1 set (male and female) 3-way XLR plugs, to connect the power supply to the amp.
  • A piece of aluminium to mount the connectors in.

Casing:

  • Use a birch plywood, 9 mm thick and alkyd-based clear varnish used for floors and stairs.

Directions

  • Make a casing for the amplifier. The whole thing can fit into a rectangle of 148.5 x 210 mm the size of half A4 sheet.
  • The top of the casing is a sheet of perforated aluminum.

  • All components of the amp are point-to-point soldered on the chip’s leads. For the power supply use a loudspeaker-cable and regular power cord to connect the components.
  • Connect the secondary coils of the transformer. The right connection will give a reading of 40-50 volts AC
  • Mount the rectifier bridge on a piece of aluminum.

  • Connect the power supply with the connectors and clamps.
  • Cut away leads 2, 6 and 11 from the op-amp (picture 1)
  • Use a third hand and non-hardening clay to fixate the parts to be soldered.
  • Start soldering the parts directly on the pins:
  • Solder the 22k resistor from pin 3 to pin 9 in pictures 2 and 3 (it’s the feedback path. The connection should be as short as possible). Cut away the protruding leads entirely.
  • Solder the 10k resistor between pins 4 and 8 (picture 4). This time, let the resistor protrude from the op-amps chassis. You need the length of the resistor’s leads to mount other parts on. Pins 4 and 8 are pretty crowded.
  • Solder the 100uF cap’s minus side to pin 8 and the 10k resistor (picture 5). Try to make “solder-time” as short as possible. By heating up the resistor it tends to get loose from pin 8.
  • Connect pin 7 to the plus-side of the 100uF cap with a piece of bare solid wire (I used jumper wire from a breadboard) (picture 6).
  • Solder the 680 Ohm resistor to pin 9. Take care not to un-solder the 22k resistor on pin 9 (pic 7).
  • Solder the 47uF cap’s minus lead to the plus-side of the 100uF cap. Connect the plus-lead of the 47 uF cap to the 680 Ohm resistor (pic 8).
  • Solder a piece of solid kern copper wire to pins 1 and 5 (pic 9). I bent the pins into a small arc so the copper wire wouldn’t roll away too easily. Let the wire protrude.
  • Finally, solder the wires to +V, -V and ground to resp. pins 1 and 5, pin 4 and pin the plus-side of the 100uF cap (pics 9 and 10).
  • Repeat for the 2nd
DIY Amplifier

DIY Amplifier

  • Connect the power, ground and signal plate.
  • Ground all the components in one place.
  • Connect a switch for volume control.
  • Start with choosing one of the XLR-plug’s pin as ground and connect it to the star ground. Also connect the star ground in the back plate with star-ground 2 on the “floor”.
  • Make leads for the V+ and V- connections with solid kern electrical wire. The wires are mounted in 16 amp connectors which are screwed onto the wooden floor. Solder leads from the XLR plug to the V+ and V-.
  • Glue a piece of alu tube (30×30 mm) over the width of the floor with epoxy.
  • Connect the potentiometer to the lines-in and ground through the heat sink. Then mount both amps on the heat sink. Start connecting the wires one by one, cutting them as short as possible. Use shrink wrap to isolate the soldered connections where possible.
  • Build a wooden case and paint it.
  • Mount the parts of the power supply in the case.
  • The toroid transformer is mounted on the floor with a 60 mm bolt.
  • Drill 2 35mm holes to fit in the big capacitors.
  • Now’s the time to play the amplifier.

This DIY amplifier has good sound and is really easy to make.

Also Read: DIY Ultrasonic Cleaner

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