Friday, December 27, 2013

Enclosure for KF5INZ "Easy Digi" Sound card interface

To follow up on the last KF5INZ "Easy Digi" post, I wanted to show you the enclosure that I made for it.  This post will be more pictures than typing, because it is easier to show than to type.  Plus I'm feeling kinda muddled this evening and am having trouble typing.  Blood sugar must be messed up again...

I decided to use the venerable Altoids tin for this project.  They work great for this sort of thing.  Plus the mints are delicious!

I decided to use 1/8" Stereo jacks for all I/O ports.  I've done this before on a past project and it works well.

I marked the locations for the audio jacks by putting them in the bottom of the tin and marking the location with a Sharpie.

If you look close, you'll notice that the line is a bit higher than the jack, this is due to the pens thickness and ends up giving a perfect location for the jack with enough room to close the lid.  I discovered this method after messing up and putting one just a bit too high.

I found the perfect method (courtesy of Don, K3RLL) for making holes in Altoids tins.  A simple, basic, paper hole punch makes just the right sized hole and leaves a nice clean edge.

You can see where I have tried using a step drill.  Not nearly as clean.  All jagged and full of burs.

Test fitting the jacks in place to verify that the lid would close with the slip ring in place.

 Now to connect the PCB to the jacks.  I started by soldering the wires to the board with plenty of excess wire to reach the connectors.  I then did a test fit to get the proper wire lengths and attached the jacks with the whole mess outside of the tin.  I used heatshrink tube to clean up the clutter.

I used two layers of double-sided tape to hold the board into the tin to avoid any short circuits.  I cleaned the inside of the tin with alcohol before sticking it down.

And the finished product!  The flash made pictures difficult due to the shiny tin, but you can see the cable routing.  This was a quick and easy project from getting to kit to having a completed and usable sound card interface!

Here are the details on the cabling.  The jacks on the left go to the rig, and the jacks on the right go to the PC.  Something like this:

Rig Left (To Rig) Right (To PC) PC
Spkr RX Audio RX Audio Mic
Mic TX Audio TX Audio Spkr
Mic PTT PTT Serial

The columns labeled rig and PC denote what ports the jacks on the interface connect to.

I hope that you enjoyed the little picture show!  Best of luck with your project.  If anyone is interested I will post about how I built the cables.


Richard, KK4JDO


  1. I read something about the transformers are providing isolation, to prevent AC Humm, caused by ground loops..
    Seems like grounded audio jacks would defeat the propose of the transformers..?.

    Maybe it might keep RF off the soundboard cables & PC.. If you had a high SWR during transmit..

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  3. Besides the grounded audio jacks circumventing the isolation The only issue I see is there is No RFI suppression. You really need to add a bunch of ferrite beads to each input and output line. There are two ways to do this external clamp on ferrites (Expensive) or ferrite beads installed internally over the wires before soldering (very Cheap and effective)