So there are a lot of ways that you can add sound to your Retropie or more specifically
Raspberry Pi arcade. One of the ways that I have seen done commonly and I think it’s
a great idea is to simply use the HDMI audio out and use the speakers that are in your
monitor. Unfortunately a lot of times monitors either don’t have speakers or the speakers
that are in them are just horrible! And sometimes I have seen people if the amplifier in the
monitor is good enough just replace the speakers, and that works fine.
What I see more often than not is that people will just use the 3.5mm output on the Raspberry
Pi and just avoid that altogether.
In my case I like to use these USB powered speakers and those work great. There’s no
amplifiers, no wiring, no nothing. You just plug those into the USB port and then you
plug the 3.5mm audio jack into the Raspberry Pi and you’re done. There is no configuration
needed.
Well, my wife has pointed out to me that this is a little bit of a problem because when
the kids are playing, specifically the grandkids, are playing the arcade its really noisy and
she can’t just walk up to it and turn it down. What she has to do is go into the software
config and then you have to move the joystick over left and right to adjust the volume.
And that’s not ideal especially if they are in the middle of playing a game.
And so what we’re going to do today is that we’re going to add a 3.5mm volume control
to the tabletop arcade using a headphone jack and it's really simple but there’s some
things you need to understand as we go through it.
So the first thing that you might think is that you can just use a regular potentiometer
to control the volume and if you only had mono output that would be correct. A regular
potentiometer can only control one channel not stereo. So there is a thing called a stereo
potentiometer (or a dual gang potentiometer as it is sometimes referred to) which can
control both the left and the right channel. So you’ll need one of those for this project.
So I recommend a 500K potentiometer, at least that’s what seemed to work for me in my
testing. And so let’s get started.
I started by setting the tabletop arcade upside down on the workbench. I selected the side
of the arcade for the volume control location, mostly because I thought it would be the most
convenient place.
The power supply will be in our way, so I just moved it over here for now.
Using a center punch I marked where I need to drill.
And this is where things get tricky because the potentiometer’s shaft will not fit all
the way through the MDF. But of course I have a fix for that!
If we drill a pilot hole through the MDF, this will allow us to use it as a guide on
the other side.
With that guide hole we can center a 1-¼” Forstner bit on the back side. According to
my measurements we need to drill approximately ½ inch deep. Take your time and go slow.
From the other side, we need to drill a ¼” hole for the shaft. I’ll use this scrap
block of wood to prevent blow out on the back side.
And with that the potentiometer fits perfectly!
Next we need to cut out 5 strips of wire. Four for the stereo channels and one for ground.
I’ll have a complete wiring diagram for this on TheGeekPub.com.
Next up I tinned the leads of the potentiometer and attached the stereo channel wires to it.
Red for left, and blue for right.
I then covered all four terminals with heatshrink tubing. This will protect them in case they
ever accidently make contact with something.
I clamped my heatgun in my vice and fired it up. Just slowly turn the tubing over the
geatgun for two to three seconds.
Using a heatgun is the proper way to shrink the tubing and won’t damage it like a cigarette
lighter.
I added a second larger tube of heatshrink around all four wires to act as a jacket.
I’m just doing a small section here, but I’ll do the whole length off camera.
Finally, we’ll solder the other ends of the wire to the headphone jack and plug, again
using heatshrink to protect them from shorts.
And these plastic covers just screw over to complete everything. There’s one for the
jack and another one for the plug.
And that completes the cable! Let’s install it!
We’ll just insert the stereo potentiometer into the cavity that we drilled out earlier
and hold it in place with a ¼” nut.
And I found this cool looking volume knob on amazon. I like it.
We’ll disconnect the speakers from the Raspberry Pi and connect the input of our potentiometer.
Then we’ll plug the speakers into the output jack.
Then we’ll drop the monitor’s power supply back in place and screw it back down.
To finish things up we’ll zip-tie the volume control’s cable in place for safekeeping.
And so the volume control is complete. Let’s try it out with a little Ms. Pac-Man. Ah yes.
My wife will be very, very happy about that modification.
Some of you have probably noticed or thought during this video, “It sure would have been
easier to install that if we had done it from the beginning.” And you are absolutely right.
And so what I am going to do (and it probably won’t be up in time for when this video
goes live) is add a volume control option in several locations so you can decide if
you want it on the back or on the side or wherever. And I will drop those in the plan
files. So you can pick where you want it and do it during construction and it won’t be
nearly as hard.
That’s all for this video. If there are any other modifications that you’d like
to see me make to any of my arcades, drop a comment below and I will see if I can do
it. See you in the next video.