CTX Assembly Guide

Safety Precautions, Warranty, and Disclaimer Improper soldering and handling of electricity can cause serious injury and damage to your property. Read and understand the instructions below before beginning your project. Follow the instructions, build carefully, and use the appropriate tools. Build at your own risk. DIY Recording Equipment, LLC is not responsible for any damage or injury resulting from the assembly or use of your kit. You are the manufacturer of your kit. It is your responsibility to turn this group of parts into a working piece of recording equipment. DIY Recording Equipment, LLC does not guarantee the success of your project and disclaims any Implied Warranty of Merchantability. Please visit the support forum for assembly support.
Damaged or Missing Parts All kits and parts are checked before being shipped to you. If something arrives damaged or if your kit is missing a part, please open a support ticket to inquire about a replacement. Missing parts will be replaced at our expense. Damaged parts should be returned for verification. If the part shows signs of use beyond what was necessary to determine that it was damaged, DIY Recording Equipment, LLC reserves the right not to replace the part.
Welcome to the CTX Assembly Guide

Thank you for purchasing a !

If this is your first DIY project ever, we recommend reading our Getting Started Guide.

Table of Contents

Required Tools

You'll need the tools below to complete this build.

Soldering Iron
We recommend an adjustable-temperature station, such as the $40 Weller WLC100.

You can use 60/40 "leaded" solder or lead-free. We recommend 60/40 because it flows better and is easier for beginners to use.

Wire Cutters
You'll need a pair of good "snips" for cutting of the excess leads after soldering.

Optional Tools

These tools aren't strictly necessary but can make your build a bit easier.

If you find the color bands on resistors a bit hard to read, you can use a meter to sort them with absolute confidence.

Desoldering Pump
If you accidentally solder something in the wrong place, a desoldering pump can save the day.

0. Resistor Calculator

Type in the value of the resistor you need and this tool will show you the corresponding color code.

Check Revision

This assembly guide is for mkI of the CTX, which was discontinued in 2019. If you bought your kit after 2019, go to the new CTX assembly guide.

Place Connectors

Identify and Sort Components

Before you begin assembly, it's a good idea to download and print the CTX Component Sorting Sheet (PDF). Sort the components by laying them out according to the sheet.

Standoffs and Connector

Insert the nylon standoffs into the four mounting holes. You should feel them snap in by inserting the flat side of the standoff into the Colour PCB. The other side is more rounded, which will make it easier to remove the Colour from the pallet.

Solder Connector

Solder the 8-pin connector with the longer leads facing down.

Place Resistors


Insert and Bend Resistor Leads

Bend the resistors and insert them into the corresponding holes shown on the silkscreen. Flip the PCB over and bend them against the holes in order to keep them in place before soldering.

Solder Resistors

Apply a small amount of solder while placing the tip where the lead meets the pad.

Trim Resistor Leads

Allow the new solder joints to cool for a few seconds and then trim the resistor leads as close as possible to the joints.

Place Larger Components


IC Socket and Capacitors

Insert the ceramic bypass capacitors CB1 and CB2. These components are non-polarized and as such have no correct orientation. Bend their leads to keep them in place. Next, insert the 8-pin socket for U1. U1 does have an orientation: align the notch on the body to the corresponding notch on the PCB legend. Hold the socket in place with your fingers or a piece of tape, flip the board over, and solder the capacitors and socket. Trim the capacitor leads as you did with the resistors. Note: We goofed and forgot to populate RLED when we took these pictures. Until we correct this, please ignore or mistake and populate RLED with all the other resistors.

Solder Transformer

Look closely at the transformer and find the four pins with small magnet wires attached to them. Insert the transformer into the PCB so that this row of pins faces the other components. The first of these wired pins will be inserted into the square pad on the PCB. If in doubt about the correct orientation, see the picture for the next step for reference. Flip the PCB over and solder in a 'zig-zag' fashion, alternating from one side to the other in order to prevent the transformer pins from overheating.

Insert IC

Finally, insert the IC into the socket. The TL071 IC's orientation is indicated by a circle next to pin one. Insert the IC with the circle facing the notch in the socket and PCB legend.

Final Checks

Before you wrap up, check the following things:

  • IC orientation: Does the dot/notch on the IC align with the notches on the socket and PCB?
  • Resistors: Do all of the resistor positions correspond the chart and/or sorting sheet?
  • Soldering: Is every solder joint shiny and clean? If one is cloudy or misshapen, try reheating it for 8 seconds and adding a tiny bit more solder.
  • Trimming: Are all of the excess leads trimmed down as close to the joint as possible?

All good? Congrats on finishing your build! Have a question or problem? Drop us a line.

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