LINE2AMP RevC v1 Assembly Guide and Manual
AssemblyThe LINE2AMP is about as beginner-friendly as a DIY kit can be. However, as with any soldering project it involves liquid-hot metal and noxious fumes. If you don’t follow safety precautions above and ventilate your workspace, you’re gonna have a bad time. You will need at least the following tools to successfully complete the project:
- Soldering iron (25w or higher)
- Needle-nose pliers
- Wire cutter/stripper
- “Helping hands”: a stable alligator clip to hold wires and components
- Desoldering braid or pump
- Don’t overheat the transformer pins. The pins are connected to the coil by a very light gauge wire that will break if overheated. The safe amount of time depends on the heat of your iron, but it should not take you more than eight seconds to solder the joint.
- Make a solid mechanical connection before solidering. Think of solder as a way of ensuring an electrical connection, not as the glue holding the components together. Employ twisting, wrapping, and crimping to make sure the wires and leads stay in place before you solder them.
Populating the PCB
1. Begin by identifying the four resistors included in your kit. If you are new to electronics, this is a good way to become familiar with the resistor color code.
2. Place the resistors in the positions shown above on the top of the PCB; then flip the PCB over and solder/trim the leads.
3. The transformer mounts on the bottom of the PCB. Pin 1 is marked by a notch on the transformer and a square pad on the PCB.
Wiring the Jacks and Switch
Determine the lengths of wire you'll need by placing the jacks and assembled PCB in the case and stretching wire between the pins you'll be soldering. Trim the wires, strip and tin the ends of each length. Identify the pins of the input jack. The three pins are tip (hot/+), ring (cold/-), and sleeve (ground), named for the segments of the plug they make contact with. The sleeve pin is indicated by a beveled edge on the body of the jack. The tip pin is that to the left of the sleeve when facing the back of the jack. Solder the lengths to the jacks and switch as shown above. You'll notice that the output jack contains two sets of pins. For our purposes, we'll use only the set that is to the left when facing "into" the jack.
Solder the black and red wires from the jacks to the PCB as shown. To make sure your LINE2AMP maintains the correct signal polarity, solder the red wires to the terminals marked "+".
Simply run a line-level signal (such as that from a audio interface, mixer, or tape machine) into the input jack of the LINE2AMP. Then, plug the output of the LINE2AMP into the guitar effect or amp of your choice. If the signal coming from the LINE2AMP is significantly noisier than the input, you might be suffering from a ground loop. In most situations, you can eliminate this noise by flipping the toggle switch to break the ground connection.
You’ll notice that the LINE2AMP does not feature a volume knob. This is due to the fact that the step-down transformer attenuates the audio signal by 18dB. In most cases this is plenty of gain reduction, but if you do require a quieter output signal you can always adjust the volume of your line-level output device.
ModificationsPlease follow the links below for modification instructions.
- Passive Pickup Emulator
- Volume control (coming soon)
- Impedance control (coming soon)
TROUBLESHOOTINGYou’re LINE2AMP doesn’t work. Congratulations! You’ve just signed yourself up for some real audio electronics learning. Having your project work perfectly the first time is nice and all, but you learn a lot more when something goes wrong. Most problems can be identified with the troubleshooting steps below.
Check Your Inter-ConnectionsDouble check that you are connecting your LINE2AMP to the correct devices and cables. The input of the LINE2AMP should be connected to a balanced, line-level output such as that from a mixer, audio interface, or tape machine via a balanced (two stripe) TRS cable. The output jack should be connected to an unbalanced, instrument-level device such as a guitar amp or pedal via an unbalanced (one stripe) TS cable. If any of these devices or connector-types are different from the above, your LINE2AMP may not work correctly.
Check the TransformerIt’s possible that you may have damaged the transformer during soldering. A simple resistance check will confirm whether or not your transformer is in working order. To get the most accurate reading, make sure no other devices are connected to the LINE2AMP. Then, set your multimeter to Resistance (Ω) and make sure the readings are within 10% of these values:
- Between pins 1 & 3: 440Ω
- Between pins 1 & 7: 0 (infinite)
- Between pins 5 & 7: 104Ω
- Between pins 3 & 5: 0 (infinite)
If all of those values are correct, the problem is not with your transformer. If the values are different, please contact me about purchasing a replacement.
Check Your Solder JointsIf you have confirmed that your connections to the LINE2AMP are correct and your transformer is not damaged, we can narrow the list of suspects down to your solder joints. Begin by doing a visual check for cold solder joints. Look for joints that are gray and cloudy instead of shiny and metallic, or that contain cracks or particles. If any look particularly eggregious, de-solder them, clean the surface with isopropyl alchohol, and re-solder them. While you are doing this, be sure not to heat the transformer pins for more than 5-8 seconds at a time. If the problem persists after re-flowing any cold joints, you can root out the culprit(s) by testing for continuity throughout the circuit. In order to test the jacks as well as the joints, plug a balanced cable into the input jack and an unbalanced cable into the output. Use a continuity tester or the resistance mode of your multimer to test for continuity between the following points:
- Input cable tip and pin 1 of the transformer
- Input cable ring and pin 3 of the transformer (the “ring” is the space between the two isolating rings of the plug)
- Output cable tip and pin 7 of the transformer
- Output cable sleeve and pin 5 of the transformer
- Resistance beetween the tip and ring pins of the input jack is the same as between pins 1 & 3 of the transformer
- Resistance between the two pins of the output jack is the same as between pins 5 & 7 of the transformer
- There is no continuity between the case and any of the pins of the transformer