This module is part of my Eurorack series. It is a simple low frequency oscillator (LFO) with an adjustable range. The output level can be attenuated and it is possible to blend between triangle and square signal.
Buy kit or PCBs in my storeKey features#
- adjustable frequency
- adjustable output level
- blend output between triangle and square signal
- amplitude 10Vpp
- frequency range 0.25-50 Hz
- easy to build, all through hole components
- 4HP
How it works#
There is a potentiometer to control the LFO’s frequency. It is generating a triangle and a square signal and the output can be blended seamlessly between both signals. It can also be attenuated with the level potentiometer. The maximum amplitude of the LFO is 10Vpp (10V peak-to-peak, from -5V to +5V). Its frequency range is roughly 0.25 Hz to 50 Hz. It gets even higher up to several hundred Hertz but it is hard to control and amplitude is going down.
Assembly#
The build is pretty straight forward. The module only consists of through-hole components and is easy to assemble. There are three boards: a front panel, a board for controls/jacks and a board for the circuit.
First, solder all parts on the component board. Keep the jacks and potentiometers for the end. Begin with the components with the lowest profile and work your way up. Screw the jacks and potentiometer to the front panel before soldering them. All components have a fixed designator and a component value printed on the board. Additional information on the parts can be found in the BOM below.
See the Component Basics guide for help identifying parts.
BOM#
Link to interactive BOM of the component board
| Reference | Value | Footprint | Description | Qty |
|---|---|---|---|---|
| C1 | 2u2 | Capacitor_THT:C_Rect_L7.0mm_W3.5mm_P5.00mm | film capacitor, non-polar | 1 |
| C2 | 100n | Capacitor_THT:C_Disc_D3.0mm_W2.0mm_P2.50mm | ceramic | 1 |
| C3, C4 | 10u | Capacitor_THT:CP_Radial_D5.0mm_P2.50mm | electrolytic | 2 |
| J1 | CONN1 | Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical | 4-pin socket 2.54mm | 1 |
| J2 | CONN2 | Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical | 4-pin socket 2.54mm | 1 |
| POWER1 | Conn_02x05_Odd_Even | Connector_IDC:IDC-Header_2x05_P2.54mm_Vertical | IDC 10-pin | 1 |
| R1 | 100R | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| R2 | 100k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| R3 | 220k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| R4 | 1k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| R5, R6 | 10 | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 2 |
| R7, R8 | 4k7 | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 2 |
| U1 | TL074 | Package_DIP:DIP-14_W7.62mm_Socket_LongPads | 1 |
Link to interactive BOM of the control board
| Reference | Value | Footprint | Description | Qty |
|---|---|---|---|---|
| D1 | Dual LED | LED_THT:LED_D5.0mm | single LED can also be used | 1 |
| J1 | CONN1 | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | 4-pin header 2.54mm | 1 |
| J2 | CONN2 | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | 4-pin header 2.54mm | 1 |
| J3 | OUT | Connector_Audio:Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | Thonkiconn 3.5mm jack sockets | 1 |
| R1 | 1k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| RV1 | B100k LEVEL | Potentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Vertical | linear, vertical, threaded, 6mm | 1 |
| RV2 | B100k LFO WAVE | Potentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Vertical | linear, vertical, threaded, 6mm | 1 |
| RV3 | RATE 1M | Potentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Vertical | linear, vertical, threaded, 6mm | 1 |
Schematics#
