Do-It-Yourself Headset

November 2019


A few years back, I posted a page about my long process for developing a slim-line headset to fit under a leather helmet.

This provided the building information in a rather round-about way.  All well and good....but for someone JUST looking to build a headset, it was perhaps a bit too confusing.

Plus some of the information is out-of-date...as in giving Radio Shack part numbers for components.  Radio Shack closed down a few years ago, so the part numbers aren't as much of a help.

This web page strips away the extraneous information.  It provides just what you need, if you're wanting to build your own headset.

This web page assumes that you need a headset that plugs into an aircraft in the normal way.  This may mean the standard pair of jacks on the panel of a Cessna, it may mean an Icom with a headset adaptor.

Building the headset will take some minor electronics work, mostly soldering wires to plugs and jacks.

Parts List:
Let's look at the Microphone side, first.

Microphone

Building your own headset microphone means solving some electrical and some mechanical issues.  Electrical, in the sense of connecting the microphone element to the microphone jack of the airplane, and mechanical, which addresses the issues of how to support the microphone on your head.

Microphone Electrical

It's pretty straight-forward, really:  There are two contacts on the microphone element, and they have to be wired to the ring and sleeve terminals on the microphone plug.

That is literally all there is to it.  The schematic on the right shows the connectivity.  The mike plug end has three electrically-separated sections, and the microphone element is connected to the sleeve portion (the longest section closest to the middle) and the ring connection (midway between the tip and the sleeve.

Pretty darn simple...and it's too darn easy to wire to the TIP, instead of the ring.  Watch that.

Why is the Tip left blank?  Because it's used for the push-to-talk switch.  Connect the tip to the sleeve, and the radio PTT is activated.  That's usually on the aircraft side of the interface, and you shouldn't have to worry about it for your homebuilt headset.  The existing PTT switch will work fine.

I like to use shielded cables to connect the microphone, as stray signals can feed back.  I use ordinary audio cable, the kind of stuff you use to connect speakers to stereos.  Connect the shield part of the cable to the sleeve on the plug.

The microphone element has two sockets with set screws for accepting wires from the plug.  As I mention in the main article, 12-gauge Romex wire is perfectly sized.  But it's really a lot easier to use a U-173/U microphone attachment plug.  This is a little assembly that costs just $2 and includes everything needed.  Buy several.


The assembly consists of an outer shell, a top and bottom for the body, and two pins.  The two pins are sized to fit the microphone element, and the assembly puts the pins exactly the right distance apart.

You'll need to solder wires to the pins, assemble the body, and slide it inside the shell, with the wires existing the hole on one end of the shell.  The wires will need to be very fine gauge to fit through the flexible neck of the microphone boom.  We'll be cannibalizing an LED flex light for the boom, just use the wires from inside of it.

Assemble the connector WITHOUT soldering wires, attaching to the microphone element (tighten down the connection screws) then remove the shell and two body halves.  This holds the pins in the right position for soldering.

This diagram shows how the wires need to be soldered to the pins.  NOT to the end of the pins but to the "wings" in the middle.



Microphone Mechanical

It's good we know how to wire up the microphone element, but it doesn't do too much good if the microphone element isn't supported by your lips.  We need some sort of structure to hold the mike.  On a standard headset, the microphone boom just connects to the ear cups.  But we're using ear buds for our homebuilt headset, so that's not an option.

The diagram to the right illustrates how I make my microphone booms.  The main part of the support is a big "U" shape of wire that goes over my ears and tucks down to the lower part of my head in back.  The boom basically rests on my ears....though, a bit later, I'll show how I modify this.  On my last several headset, I've used some Romex wire (solid copper house wiring), doubled it, and bent it into shape.  The frame goes over the other ear in exactly the same way.

You can see the U173 plug that connects to the microphone element (hidden under a foam cover in this illustration).

Between the two, you see something labeled "Flex Tube".  This is metal tubing that bends...the microphone wires run on the inside of the tubing, and the tubing itself is attached to the main frame (I use safety wire wrapped around the two).  The cable to the microphone plug connects to the microphone wires outside the flex tube, then follow the route of the bent frame.  The whole frame is covered with shrink tube when it is all together and working...including the area where the flex tube is wired to the frame.

You don't HAVE to use the flex tube.  You can run the Romex frame right down to the U-173 plug, bending it as appropriate to put the mike element on the corner of your lips.   But for the most part, the flex tube is nice...you can pivot the mike away from your lips if you want, and it's more adjustable than the hard bending of the Romex.

So, where do you get this flex tube?   I bought a flexible LED light from Amazon (designed to plug into a USB port, and used the flex tubing from it.  Search Amazon for "LED Flex Light"; they sell for about $10 and provide enough flex tubing for two headsets.

Try not to damage the wires inside; you can re-use them to connect your U-173 plug to the coaxial cable that goes to the microphone plug.

From this point, it's just assembly.  Wrap the flex tube and end of the frame together with safety wire, cut the flex tube to the right length, epoxy the U-173 shell to the end of the flex tube (you might have to ream out the shell slightly), then run the wires from the U-173 connector through the flex tube, solder them to the audio coax you're using to connect up the microphone, and route the coax along the frame.  Use a bunch of black shrink tube to cover the whole frame and the interface with the flex tube (don't use the shrink tube on the flex tube itself), run the cable for ~3 feet, and install the plug.


One final fillip:  While the microphone boom is light, it's still putting some weight atop one's ears.  I actually found it a bit uncomfortable.

So I added a support strap, as you see in the picture to the right.  This is just a strip of velcro, with the ends curved around the parts of the frame that go over the ears.  I size this so the frame sits slightly above my ears and takes all the weight off them.  It's very comfortable.

Headphones

Compared to the microphone, there's little work required for the headphones.

Just about any commercial ear plug/ear bud will work.  I have a set of ear buds that actually an automatic noise limiter (ANL), like the top-of-the-line aircraft headsets.  These were expensive for ear buds ($100) but it's still hundreds less than a standard ANL headset.

I found a better options:  Plugfones.  These are foam ear plugs with speakers built into them.  They have passive noise attenuation equal to those of a standard headset, and provide very good volume to the ear.  What's more, they're cheap (about $25) and you can buy spare ear tips cheaply as well.

I *really* like these.  I hate standard ear buds because they're hard; these are soft and very comfortable.

They actually have two types of ear tips.  One is the standard, foam like the typical ear plugs.  The others are flanged silicone rubber, similar to ear plugs used for percussive sports like shooting.

One huge advantage of these is their low cost:  You can put a spare set or two in the airplane, and have some backup headsets.

The big DISadvantage of these is that they have an 8-ohm impedance.  Standard aircraft radios expect speakers with 300-ohm impedance, and these won't work without a matching transformer.

Connecting to a Handheld

But if you're connecting your homebuilt headset to a handheld radio, you don't NEED a matching transformer.  The handhelds want an 8-ohm speaker, and that's what ear buds supply.

So all you need is a way to plug the 1/8" plug for the ear buds into the 1/4" jack on your radio's headset adaptor.  That's real easy, nominally... they sell simple adaptors that allow plugging-in a 1/8" plug into a 1/4" jack.  Often, these adaptors even come with your ear buds.

However, there's a problem:  The ear buds (and adaptors) are set up for stereo (two audio channels), but the radio only outputs one.  That means only one of your ear buds will work.

The good news for those willing to spend $10 is that you can BUY adaptors to do the job.  Check on Amazon for a "1/4 Mono to 3.5mm Stereo Adapter".  This one is $10 for two, and they work just fine.

If you've got a stereo adaptor just sitting around, you can modify it as shown below.  Cut a slit between the tip and ring of the adaptor, then fill the slit with solder to connect the tip and ring.  I used a Dremel tool with a cutting wheel to cut the slit, but you can probably do the same thing with a triangular file.  Just smooth the solder down afterwards so it goes into the jack without effort.



Connecting to an Aircraft Radio

For the ear buds to work on an aircraft radio, a small impedance matching transformer has to be used.  I use an XICON 42TL004 transformer, purchased from www.mouser.com.  They're just $4 or so, I'd pick up several to have spares.

The "Primary" side of the transformer is marked with a large black "P".  The two outer connections of the Primary side are connected to the plug going to the aircraft radio, while two outer connections of the secondary side go to your ear buds.

The following diagram shows how the impedance matcher should be wired.  A 1/4" plug is connected from the aircraft headset jack to the PRIMARY side of the transformer, and a 1/8" jack is connected to the secondary side.  Because (again), the ear buds will be stereo, the tip and ring connections on the 1/8" jack are wired together to give the same signal to both channels.

The biggest problem right now is that jack for the ear buds.  This is a 1/8" inline stereo jack, but I'm having trouble coming up with a definitive part number for it.  Radio Shack used to carry them, and I've found them on the shelves at various electronic component stores, but can't seem to pin down a specific part number to help you order them.

One way to do this is by installing the transformer inside a small plastic box, with a standard 1/8" stereo jack.  Search for "1/8 stereo jack" and you'll get a lot of options.

Feedback Squeal

When I first used this adaptor with a standard aviation headset, I got a squeal in the headphones when I transmitted.

It appears there was some sort of acoustic coupling between the headset microphone and the headphones.  Not sure why this happened on the handheld radio with the adaptor vs. a standard aircraft radio without an adaptor.

But the solution was pretty simple:  I reduced the "sidetone" volume.  "Sidetone" is when you hear your own voice when you transmit.  Most, if not all, handhelds should have an adjustment for this.  Here's the instructions for my Icom ICA5 (and I'm betting most radios work this way).

1.  Select an unused frequency
2.  Turn the volume down a bit so the squeal won't hurt.
3.  Press the Push-to-Talk switch to transmit
4.  WHILE transmitting, adjust the volume down.

At some point, the squeal will stop, and you will still be able to hear yourself talk (albeit at a lower volume level).


Ron Wanttaja
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