MAX™: D.I.Y. XLR Probe Instructions

The JL Audio MAX™ Measurement System has two high-level XLR inputs that can be useful for taking high voltage measurements (up to 40vRMS), such as those from an automotive amplifier. This document shows how to assemble probes that can be used with these inputs, and others like them. If you are not using the MAX™ Measurement System, be sure to confirm the capabilities of your measurement system before taking measurements.

You'll be using pins 2 and pin 3 on a male XLR plug as your positive and negative leads, these should go to 4mm banana plugs that are commonly used for test probes. This will allow you to use various different probe types for your measurements based on application. For the ground connection (pin 1), we recommend using an alligator-style connection to allow you to clip it to the proper ground point in the vehicle (when needed). Generally a total length of about 6 feet is desirable but you can make your cables a bit shorter or longer as needed by your bay / testing rig. 

Image depicts Connector-Side view of XLR pin configuration (AES Technical Standard)

Before beginning, test to make sure that none of the pins have any internal connections between them (no continuity between pins). Then, solder the positive wire to pin 2 and the negative wire to pin 3. We recommend using test lead wires that are 16AWG or larger (as large as your XLR or banana plugs will accept). Once all connections are made, check them with your multi-meter for continuity between the pin and cable. Best practice is to also add heat shrink to each connection, then give them a good tug to make sure everything is done right before closing up the back side of the XLR plug. On the other end of each wire, secure your banana plugs in a similar fashion.

Image 2: Soldered and heat shrunk connections

Image 3: Banana Plug (4mm) Probe ends - for use with multiple probe brands and types

If you plan to make two sets of probes, it can be helpful to use different color wires for the positive and negative leads to help identify them while in use (for example, grey and grey with black stripe for one set, and white and white with black stripe for the other). The ground wire can be the same color for both probes, green is the most common color for this wire. 

When taking measurements of speaker wires, use the positive (pin 2) and negative (pin 3) probes on the positive and negative wires. The ground can be used to connect to a common ground if you should have some noise issues on your readings. Do not use pin 1 for voltage measurements!