UralTone Optic-28 is traditional optic guitar compressor. It uses carefully selected LDR / LED pair for adjusting the gain of its OP AMP circuit. The imperfection of LDR (light dependent resistor) and light sources is what makes optical compressors interesting. Every type of LDR and light source (lamp, led) has its own kind of attack and release curves.
You can use it as a solo boost to overdrive your tube amp and add little bit compression to make your guitar sing. You can tighten up your rhythm guitar sound or make your clean solo guitar sound really tasty.
Features
Knobs: Compress, Volume Switches: by-pass Power supply: 9V battery or 7-12VDC power supply Size: 80x55x21mm (box measures)
Follow the assembly order in the images below. We strive to keep the component models consistent, but the electronics market evolves rapidly, and sometimes we must switch manufacturers or series due to availability. If a component looks slightly different, don’t worry—each component has its value printed on its body.
Start the build with the footswitch. The first component to be soldered is the LED resistor. This resistor is packed separately in the hardware set bag.Press the footswitch onto the board. Note the installation direction—there is a notch in the threaded part that should face upward. The solder pads on the board are tight, so inserting the footswitch may require some force and persistence. The PCB and switch are durable enough to withstand this.Cut five-centimeter pieces from the wire included in the kit. Strip about 3mm of insulation, twist the strands together, and pre-tin the stripped wire ends. NOTE: Do not install the LED at this stage!Set aside the footswitch board and move on to the main effect circuit board. Start by soldering the resistors onto the board. Always begin with the lowest-profile components to ensure they remain flush with the PCB when flipped for soldering.Solder the IC socket onto the board. Note the notch in the socket, which indicates the orientation of the IC. Align this notch with the marking on the PCB.Install the film capacitors in their designated positions.Install the transistors in their designated spots. Their orientation is printed on the PCB to match the shape of the transistor casing.Build the opto-isolator. You can tape the LED and light-dependent resistor (LDR) together with clear tape to make it easier to insert into the heat shrink tubing.Slide the components into a suitably sized piece of heat shrink tubing and heat it until it shrinks. Squeeze the ends shut to prevent light leakage into the LDR. When enclosed, light leakage is not an issue, but the device cannot be used in bright light with the case open. NOTE: The LED is on the left in the image, distinguishable by its different leg lengths.Install the completed opto-isolator onto the PCB. Observe the LED polarity and the orientation as shown in the image.Solder the opto-isolator onto the board.Solder the electrolytic capacitors into place. Observe polarity—the white stripe indicates the negative lead.Side view of the electrolytic capacitors.Insert the IC into the socket. The orientation follows the PCB markings or the notch on the socket. Pin 1 is usually marked with either a small dot or a notch.Solder the potentiometers into place. First, solder just one leg to hold the potentiometer in place. Adjust its alignment if necessary, then solder the remaining legs.Solder the previously assembled footswitch board and battery clip. You may shorten the battery clip wires by about 5cm.Install the jacks into the enclosure. Place a star washer between the enclosure and the jack.Insert the DC jack into the mounting hole.Insert the LED into its mounting hole. Pay attention to the LED polarity. The shorter leg / beveled side is marked on the board. When viewed vertically (wires up), the beveled side / shorter lead should be on the left.This assembly is inserted into the enclosure.Install the circuit boards into the enclosure. First, thread the battery clip wires underneath the output jack. Be careful when installing the circuit board to ensure the DC jack does not fall out of place. (You can use an unpowered DC plug or adapter to hold it in place). If desired, install the faceplate. Hand-tighten the nuts and align the board neatly in place. Once everything fits correctly, solder the DC jack. The LED is installed by inserting it through the faceplate and soldering it in place.Solder the jack wires in place.
NOTE: UralTone kits use two different types of input jacks. Before soldering, check which version of the jack is included in your kit: https://en.uraltone.com/blog/input-jack/
Tighten the nuts on the faceplate and attach the potentiometer knobs. The effect pedal is now ready for testing!
Enjoy your playing!
If you have any questions or feedback, don’t hesitate to contact us!
Wellcome to our new blog site. We have tons of building instructions and other material in Finnish that we are currently translating to english. So lost of new material is coming soon!
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