1Wamp: Open Hardware 1 Watt Guitar Amplifier.

By on January 5, 2016

Web site:

http://www.electrosmash.com/1wamp

Project Summary:

1Wamp is a 1 Watt guitar amplifier loaded with all the features of big amps. It was developed using free open source tools and there is a detailed electronic analysis so everybody can contribute improving it or adding mods.

This portable amplifier features:

- Tone/Volume/Gain controls.
- Speaker/Cabinet output.
- Headphones output with attenuator switch.
- Aux/mp3 input.
- Battery clip.
- 9V DC boss style power input jack.

Full Project:

The preamp stage with two J201 transistors is designed to give a tube-like sound, the Big Muff Pi style tone stage is able to produce a big range of tones and the LM386 output stage can drive 1Watt into any kind of speaker, from headphones to a Marshall 2×12 cabinet.

1Wamp-functions

There is a quick start guide explaining  How to build 1Wamp in 5 Steps

In 1Wamp Forum you can share your ideas and check topics like “how to fit the PCB in an enclosure”, use the lightplates, etc…

1Wamp Open Source Guitar Amplifier

Circuit diagram:

The schematic was developed using easy-to-find components:

1Wamp Schematic

The circuit can be broken down into 5 simpler blocks: JFET Input Stage, Tone Control, JFET Booster, LM386 Power Amplifier and Power Supply:

1wamp-schematic-blocks

The functionality is simple: The input stage isolates the amp from the guitar, keeping the signal quality and avoiding tone sucking. Then the tone control shapes the frequency response adding more bass/treble to the mix. The JFET booster will recover the signal after the tone control and prepare it to the Power Amplifier stage that delivers up to 1W.

The aux/mp3 input adds any line level input signal to the guitar sound, allowing to practice with metronome/mp3/youtube backing tracks.

There is a full analysis of every single part of the circuit, so you can understand the functionality of any component and mod or tweak it for your taste (cleaner sounds, more distorted, equalization..)

Bill of Materials:

There is a PDF with the Bill of Materials: 1Wamp-bill-of-materials

Find also below the complete bill of materials, with Mouser/Farnell references and alternatives:

1Wamp Bill of Materials
Reference Qty Value Description Mouser Farnell
Capacitors
C1 1 6.8n Capacitor R82EC1680Z350J
C2 1 10n Capacitor R82EC2100DQ50J
C3,C4,C6 3 47n Capacitor R82EC2470DQ60J
C5,C11,C12 3 100n Capacitor R82EC3100DQ70J
C7,C8,C9,C10 4 220uF Capacitor REA221M1CBK-0811P
Resistors
R12 1 10R Resistor MF25 10R
R13,R15,R16 3+2* 1K Resistor MF25 1K
R3,R8 2 2K2 Resistor MF25 2K2
R2,R7,R11 3 6K8 Resistor MF25 6K8
R5,R9,R10,R14 4 22K Resistor MF25 22K
R4 1 47K Resistor MF25 47K
R1,R6 2 1M Resistor MF25 1M
Pot1,Pot2,Pot3 3 50K Potentiometers RK09D113000D
Connectors
CON1, CON3 2 6.35 jack. Jack NMJ6HCD2
CON2 1 3.5 jack Jack FC68125
CONN4 1 2.1 jack Jack KLDX-0202-AP-LT MJ-179PH
Others
D1 1 1N5817 Schottky Diodes 1N5817
D2 1 LED Standard LEDs mm VLHW4100
D3,D4 2 1N4733A Zene Diode 1N4733A
8pin dip socket 1 8Pin IC 4808-3000-CP
Q1,Q2 2 J201 JFET transistors.
Plastic Knobs 3 6.35mm Knob 6.35 mm 450-2023-GRX
SW1 1 switch Toggle Switch 612-100-A1111
9V Batt Conn. 1 Clip 9V Battery 121-0526/I-GR
U1 1 LM386 Audio Amp LM386N-4/NOPB
Mechanical
PCB 1  PCB
Plexiglas Cover 2
Nylon Spacer 4 m3x16 Spacers R30-1611600
M3x12 screws 8 M310-PRSTMCZ100
Batt. opt clips 2 TAB38250568(MSTIN) TAB38250568
* Add Comp.
R2, R7 2 10K Resistor MF25 10K
R3, R8 2* 1K Resistor MF25 1K

PCB:

The PCB was developed using only free / open source tools: KiCAD.1wamp-pcb-tracks-render2

  • 1Wamp is an Open-Hardware project, so all the files are open so anybody can work with them: 1Wamp-Kicad-project
  • The transfers for the PCB are also available so in case you want to do your own PCB at home: 1Wamp-layout-transfers

 

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