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Eurorack LFO

Eurorack Modular Lfo Utility Easy-Build Through-Hole

This module is part of my Eurorack series. It is a low frequency oscillator (LFO) with an adjustable frequency range. The output level can be changed and blended between triangle and square signal.

The PCBs are available in my store

Key features
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  • adjustable frequency
  • adjustable output level
  • blend output between triangle and square signal
  • amplitude 10Vpp
  • easy to build, all through hole components
  • 4HP

How it works
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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).

Assembly
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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.

BOM
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Link to interactive BOM of the component board

ReferenceValueFootprintDescriptionQty
C12u2Capacitor_THT:C_Rect_L7.0mm_W3.5mm_P5.00mmfilm capacitor, non-polar1
C2100nCapacitor_THT:C_Disc_D3.0mm_W2.0mm_P2.50mmceramic1
C3, C410uCapacitor_THT:CP_Radial_D5.0mm_P2.50mmelectrolytic2
J1CONN1Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical4-pin socket 2.54mm1
J2CONN2Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical4-pin socket 2.54mm1
POWER1Conn_02x05_Odd_EvenConnector_IDC:IDC-Header_2x05_P2.54mm_VerticalIDC 10-pin1
R1100RResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor1
R2100kResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor1
R3220kResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor1
R41kResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor1
R5, R610Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor2
R7, R84k7Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor2
U1TL074Package_DIP:DIP-14_W7.62mm_Socket_LongPads1

Link to interactive BOM of the control board

ReferenceValueFootprintDescriptionQty
D1Dual LEDLED_THT:LED_D5.0mmsingle LED can also be used1
J1CONN1Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical4-pin header 2.54mm1
J2CONN2Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical4-pin header 2.54mm1
J3OUTConnector_Audio:Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHolesThonkiconn 3.5mm jack sockets1
R11kResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal1/4W 1% resistor1
RV1B100k LEVELPotentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Verticallinear, vertical, threaded, 6mm1
RV2B100k LFO WAVEPotentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Verticallinear, vertical, threaded, 6mm1
RV3RATE 1MPotentiometer_THT:Potentiometer_Alpha_RD901F-40-00D_Single_Verticallinear, vertical, threaded, 6mm1

Schematics
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