How to build a Soundeasy probe?

Making a soundeasy probe should be an easy task if you have some skills in electrical engineering. Otherwise, following the schematic on the soundeasy help section can be a little confusing. This guide will show you how to make a rig, that you can use to make impedance and SPL measurements. This means you will need to make the soundeasy probes. Also the rig will feature RCA cables and adapters, so that you have to make fewer solder operations. Also the rig can be disassembled at every joint.

Stuff you will need

I’m gonna list the stuff you will need and links to where you might find them. I’m using high quality connectors and cables, because I used cheap ones before and had all kinds of problems. For cable I used 2.5 mm2 in cross section, which is 14 AWG. A bit thick for this application, but when impedance is important, the ticker and shorter the cable, the better. Here is the list of the components needed (Amazon affiliate paid links) :

I need the XLR to RCA cable because I use a Focusrite Scarlet 2i2 (Amazon affiliate paid link) audio interface. If you use something else, with different input connectors, get the appropriate cable. Additionally, you will also need a soldering iron, solder and electrical tape.

Soundeasy jig build

This will actually teach you how to make a plug and play soundeasy jig, but also how to make the soundeasy probes. Here is the schematic of the jig :

soundeasy probe jig schematic

The schematic is pretty self explanatory, but I want to make a few clarifications, where confusion might occur. When you are soldering the cable that goes from the amplifier to the first RCA male connector, you will connect the positive terminal only, which you will find in the middle of the connector. Same goes for the last cable that connects to the speaker (the RCA female socket -> alligator clip -positive side). This might be confusing, since the connector has a positive and negative terminal, yet we are connecting just the positive lead. You can connect the negative side to the ground, but it’s not mandatory. However, when we get to building the soundeasy probe, that’s a different story.

Soundeasy probe build

Let’s start building the probes! Gonna go step by step, with pictures.

Step 1

Get one RCA male connector and disassemble it. Take the screw off as well.

rca connector malerca connector mare disassembled rca connector male disassembled 2

Step 2

Get the RCA female socket and stick it inside the RCA male connector. After that, screw in the tiny screw firmly.

rca male female connector socketrca male female connector socket 2rca male female connector socket 3

Step 3

Get the 47 kOhm and 22 kOhm resistors. Make sure they are low wattage ones. This will ensure that they have a small footprint. 0.25 W will work nicely with our setup, as they have to fit inside our little contraption-adapter thingy. Snip the ends of the 47 kOhm resistor.

rca adapter resistors rca adapter resistors 2

Step 4

Place the 47 kOhm resistor between the positive poles of the RCA male connector and the RCA female socket. No soldering is needed here as I managed to fit the resistor snugly in place. Here are 2 pictures, one with flash, and the other without.

soundeasy probe half complete 2 soundeasy probe half complete

Step 5

Now it’s time to test your soldering skills. First of all, fetch the 22 kOhm resistor and solder one end to the positive pole of the RCA female socket. Secondly,  solder the other end to the negative pole of the RCA female socket. This will effectively solder in place the 47 kOhm resistor as well, but only at one end. After that, i used some superglue to make sure the whole thing is tight. Don’t want to rely only on that tiny screw. After you are done, make sure you repeat the process, as you need two soundeasy probes. Here is how it should look like :

soundeasy probesoundeasy probe 2soundeasy probe 3

Make sure the wire from the 22 kOhm resistor doesn’t touch the golden part of the adapter (the negative pole of the RCA male connector). Probably You should use some electrical tape to ensure this, but I haven’t bothered. And now the probes are complete.

The 10 ohm resistor thingy

Besides the probes, I installed the 10 ohm resistor in a similar fashion. Problem was, the resistor was rated at 1 watt, and it was pretty bulky. As a result, I had to get creative, as it didn’t fit in our adapter. I got the RCA male connector and the RCA female socket as before, but I used the casing from the RCA male connector as an extender. I have snipped the ends of the resistor, but not as short as before. Soldering was needed at both ends, since it didn’t fit tight as before. And the rest was glued in place, so it stayed in one piece.

10 ohm resistor connector10 ohm resistor connector 2

Final thoughts

Here is a pic with the final jig, resting on the floor apparently :

soundeasy jig

This jig has several advantages. It’s completely modular. Every piece can be plugged or unplugged. If a soundeasy probe is faulty or malfunctioning, simply plug it out and repair it, or replace it. It doesn’t take much space. On the other hand, it can get quite expensive, if you use quality connectors like I did. However, it shouldn’t be a problem if you use cheaper ones, but I had a bad experience with them before, and I pretty much avoid them.


  1. Image source : link.