A Few Words on TPA3116D2 Audio Amplifiers

My plan for sound on the Kraylix arcade cabinet is to use two 4″ JL Audio speakers plus an 8″ woofer for bass. Of course part of having an integrated all-in-one solution for an arcade cabinet means some form of audio amplification is needed – I’m not about to cram a stereo receiver in the cabinet or something along those lines! Thankfully there are tons of decent and cheap audio amplifier boards available these days.

The TPA3116D2 is a popular chip by Texas Instruments used these days in audio amps. It’s very power efficient and hence doesn’t need a large heatsink. Small complete boards using these chips are extremely cheap and readily available on eBay for between 10$ and 20$ including shipping! I did a bit of reading on them online and it seems like results are mixed – but at those prices why not take a gamble and buy a few different ones to test them out? They seem like too good of an option to pass up, especially compared to other options for amps which can easily get in the 100$+ range. I bought three different ones in the “2.1” configuration (two main channels plus a subwoofer channel), each under 20$, hoping for at least one “good” one. I hooked them up to some small speakers plus an 8″ sub for testing. Here are my observations after listening to each for a few hours.

Heres’ the first board I tried:

Kraylix-audioamps 001

It didn’t have screw-down terminals for the speaker wires, so I had to solder the speaker wires in directly. Not a difficult task, but my speaker wire was fairly heavy gauge and the small holes on the board wouldn’t fit all the strands! I cut roughly half the strands away and soldered the speaker wires in. This board has a 1/8″ mini jack for line-in, and three dials – sub volume, main volume, and overall (sub+main) volume. So, how did it sound? Pretty decent, actually! I played a range of music and videos, including bass-heavy songs that would push its power consumption quite hard – no problems at all, and the board didn’t even get hot under prolonged testing. Then I paused the music and noticed a problem – an audible whining noise coming from the speakers. This board seems to have noise problems that are pretty obvious when audio isn’t playing back, no matter what the volume knobs are set to. Bummer. I even tried with two different power supplies (which are not included) but got the exact same results with both.

So, I moved on to board #2 to test, hoping for cleaner audio:Kraylix-audioamps 002

This board has the same volume control configuration, but came with nice knobs to install on the potentiometers. And notice how it also has screw-down terminals for not only the speaker wires, but also for the power supply in case you don’t have one with the right connector. Those are nice features over the first board. So how did it sound? Clean! Good sound at this one, and no audible whining noises! This one would work nicely in the arcade cabinet.

But I had yet another board to try out – here’s board #3:Kraylix-audioamps 003

The nice knobs came pre-installed, it has screw down speaker wire terminals, and it uses RCA jacks vs the 1/8″ mini-jacks on boards #1 and #2. I got nice clean sound out of this one, too! But the biggest difference between #3 and the other two were actually in the configuration of the dials – where as the first two had only volume controls, this board has two volume controls (sub, main) and the third knob is a low-pass filter frequency control for the sub channel. This is a very useful feature for tweaking the sound of the woofer, and for that reason I will most likely use this board in my Kraylix arcade cabinet.

Those were the main differences I found. There were some common points, too, though – they all produced very reasonable volume levels without any clipping, and none of the boards heated up much at all. The bass channel of all three sounded pretty similar, too, and although these boards are advertised as 2.1 channel (where the .1 is a subwoofer channel), I think it’s a bit of a stretch to call it a subwoofer channel. They all sound to me like the output drops off significantly below say 100hz or so. They’re more like a bass channel, which honestly will suit my arcade cabinet build just fine.

For what it’s worth, I have no idea how consistent the quality is on these boards, or why I got a whining sound from the first one but not the other two. It’s possible my board #1 was just a bad copy, but who knows. It’s hard to argue with the price – I think these boards are a tremendous value.

My plan is to install board #3 inside the Kraylix, right next to the coin door – this should allow for easy access to the volume controls while playing.

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Fabricated Kraylix Marquee Holder

With the cabinet off getting painted, I turned my focus to other parts of the build. First off, the artwork! I’ve been working on customizing my control panel and marquee art for a while now, and it’s finally done and off to the print shop. While the marquee will be back-lit and the control panel will not, I decided to do the entire art on backlit film – it makes for just one file to print, and it’s an easy way to assure the colors will be consistent between the control panel and the marquee.

I then started looking at how to mount the artwork to the marquee. The Kraylix kit came with a clear plastic panel for mounting the marquee. It’s presumably acrylic, but I’m not certain about that. The marquee art could mount either in front or in back, but with just four screws to hold it down I’m not sure I like either option – I would prefer to have something that will keep the artwork absolutely flat to the marquee clear panel. I was curious what other builders were doing about this, so after reading some forum posts I found a solution I really liked – sandwiching the artwork between two clear panels! I went to Tap Plastics and bought a sheet of 1/8″ clear acrylic to fabricate my own custom marquee holder.

Tap Plastics cut my acrylic to the proper size, but there are still a few items that need taking care of – rounding the corners and drilling some holes. I clamped some wood blocks to each side to give the material some stiffness and started with the coping saw to cut the rounded corners, using the original panel as a template. Acrylic is a very hard material and it quickly became obvious doing a rounded corner wouldn’t be easy…Kraylix-marqueeholder 002

So, I turned to the Dremel. What an awesome tool. I first used the cutting wheel to do a series of rough cuts right outside my cut line:Kraylix-marqueeholder 003

Then moved over to the sanding barrel tool to smooth out the curve and get right on the desired line. Make sure you wear proper eye protection while doing this, by the way, as hot molten plastic bits will fly!Kraylix-marqueeholder 004

Much easier and faster than the coping saw! All that was left was drilling the holes for the screws that attach it to the cabinet, and I used a purpose-made drill bit for drilling into plastics. Notice how it has a much more acute tip vs a conventional drill bit:Kraylix-marqueeholder 005

Four holes later, all done! Both pieces are clear, by the way, they are simply covered with protective film:

Kraylix-marqueeholder 006

My custom holder (above, bottom) has the same shape as the clear plastic that comes with the kit (above, top)- all for 7$ and about 15 minutes of work. Of course I could have just ordered a second marquee panel with my original order from Kray, which is what I would recommend to anyone ordering in the future… If you didn’t, though, fret not – it’s pretty easy to make your own.

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Painting the Kraylix Cabinet

After much consideration, I finally decided to have someone else paint my Kraylix cabinet for me (although I did the prep). The decision came down to not having a great space to do the paint in, and the desire to use automotive paint which is far more durable than rattle-can spray paint. I’m particularly concerned with the edges of the MDF, which can soak up quite a bit of paint – thankfully my cabinet will be in good hands with someone who’s done this sort of project before. I wrapped the top bezel in plastic and slid it into the bed of the truck on some foam sheets: Kraylix-paint 001

A cargo strap went around the whole lot to secure it, and off it goes! Can’t wait to see what it looks like when the paint is done.

That said, I couldn’t help myself – I kept a few pieces that won’t be visible when playing to paint myself. These are the marquee back panel, the monitor mounting bracket, and the cabinet back panel (from bottom to top, below). The first of these three pieces will be painted white – it will get white LEDs later to light up the marquee, and the white paint should help spread & diffuse the light better. The latter two parts will get painted black, just like the rest of the cabinet.

My poor-man’s paint booth? The back yard 🙂 Thankfully it was a very calm winds day, so the parts would stand up on the sawhorses without any fuss.Kraylix-paint 002

Here are the parts after a few layers of primer. The biggest problem when painting anything outside a proper spray booth is dust & contamination ruining your finish, but I’ve found that as long as what you’re painting is a vertical surface, contamination is greatly minimized (especially on a calm winds day). Spray paint on a part makes for an extremely sticky surface until the paint is cured, of course, so it’d be much more difficult to get decent results with a horizontal surface.

The primer dried relatively quickly in the sun, and after a light sand it looked pretty good! The marquee back panel got some gloss white, and the other two got gloss black. It’s hard to tell from photos, of course, but here are the two black panels after a few layers – they look pretty respectable!Kraylix-paint 003

I’m already counting the days until the cabinet is ready to be picked up, but in the meantime I have plenty of other parts of the build to focus on – getting the marquee & control panel art finalized and printed, and getting all the controls & electronics ready.

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Assembled Kraylix Gaming PC

As I described in my Kraylix opening post, my Kraylix arcade cabinet will be both JAMMA capable (primarily to play Capcom CPS-2 games) but will also have a modern gaming PC to play more modern titles such as Street Fighter IV and Street Fighter V. Sure, a PS4 would be cheaper, but I like the ultimate flexibility that comes with using a PC. A few days ago, I went to Fry’s and picked up the components necessary to put the PC together. At times like this, I really like shopping at Fry’s – their prices are very competitive, and you can’t beat picking out parts and having them right there on the spot.

At first, I thought perhaps I would make my own motherboard mounting bracket to install directly in the cabinet, but after thinking it over I decided to go with a standard computer case. It simplifies the mounting of other parts such as the power supply, storage disk and graphics card. Graphics cards in particular are pretty hefty these days, and I really didn’t like the idea of having it hang on the motherboard just by the PCIe connector. The case also grounds, shields and protects the components inside the PC – since there will be other parts in the cabinet, that is an important consideration. Here’s the Mini-ITX (compact) form factor case I ended up using test-fit in the cabinet:Kraylix-pc 003

The case is a Thermaltake Core V1 and definitely fits very nicely into the cabinet with plenty of room to spare for the eventual installation of CPS-2 boards. As compact as it is, it fits a full size ATX power supply and has plenty of space for a modern graphics card, too:Kraylix-pc 001

And here’s the top-down view. I’m using the OEM Intel CPU cooler, but there’s room to upgrade to potentially upgrade to something better, too:Kraylix-pc 002

Note how the Mini-ITX motherboard is barely larger than the CPU cooler! It’s tiny. Here are the full specs of my build:

  • Intel Core i5 6500 (Skylake) CPU
  • 16GB DDR4 RAM
  • Nvidia Geforce GTX 960 GPU
  • 480GB SSD

Should run most modern games (as of 2016) at or near 60fps @ 1080p, and all in a super compact form factor. The computer will get modified to remotely operate the power button later on, but for now since the cabinet was just about to go out for paint I just needed to make sure everything would fit together well. And it does! 🙂

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Prepared Kraylix arcade for paint

With the Kraylix cabinet assembly complete, it was now time to prepare it for paint. The Kraylix has many chamfered edges which need to be sanded down smooth. Thankfully MDF (which the cabinet is made of ) sands down very easily – I able to get through most of it with just one evening’s worth of work. Boy does it ever make a mess though, you’ll rapidly get sawdust all over when sanding MDF! I recommend wearing a dust mask or respirator to avoid breathing that stuff in. MDF thankfully mean the surfaces of the panels themselves are super smooth and don’t require much prep.

Perhaps the biggest piece that required prep before paint was the top arch. It’s a sandwich of multiple layers of MDF (pre-fabricated by Kray) – although the edges line up pretty close with the cabinet, it’s definitely not perfect and some type of filler is necessary to seamlessly blend the pieces together. Here’s a look before any filler was applied:

Kraylix-sanding 004

Notice the big quarter-circle gap in the chamfered edge in particular – that will need to be filled in. I used Bondo Gold as I had problems when working on the Space Shuttle cabinet with Bondo (the regular kind) clogging up my sandpaper very rapidly – the Gold kind definitely seemed to perform a bit better in that regard.

Here’s a view of the outside edge of the arch – the sandwich layers are clearly visible, but what you can’t see as well is even though I’ve started with the sanding, the layers don’t feel completely flush to each other. That will also need filler. Anything that you can catch your fingernail on would be completely obvious once painted, and the goal is for this to look like one smooth continuous surface. There’s also obviously a gap between the arch and the side arm below that will need filler as well.

Kraylix-sanding 005

Here’s the inside of the left part of the arch after a few rounds of Bondo and sanding. More sanding is still needed, but the quarter-circle gap is gone! Note that the half-circle gap you see will be behind the marquee and hence not visible, so it’s not worth filling it in. Kraylix-sanding 001

And here’s the outside of the arch once close to finished – a pretty smooth transition between each of the faces and edges now!Kraylix-sanding 002

I got the top arch and a few minor other patches over the rest of the cabinet done in about a day’s work on the weekend.

A few tips on using body filler:

  • Mix small batches at a time as it will start to cure the moment the two parts are mixed together. I seemed to have a few minutes working time at the most before my filler would start to solidify and be hard to spread. Fast curing does mean less of a wait to shape & sand, though!
  • Apply as little as possible to get the desired results. Any time you use more than required, the excess will need to be sanded which makes a mess and isn’t fun.
  • Before the filler fully solidifies, you can carve out any excess with a blade – the “cheese grater” approach. Indeed, it kind of feels like slicing through cheddar cheese!
  • If you have a large area to fill in, multiple passes are needed. Build layer upon layer instead of trying to fill it in all at once.
  • Don’t breathe that stuff in as you sand – wear a mask or respirator!

Same procedure for the control panel, which I completed the next day. This is the part your hands will rest on when playing, so I definitely took the time to sand everything down completely smooth. Kray ships the control panel pre-assembled and there was already filler between some parts, but some screw holes on the side edges need to be filled in and I went ahead and patched a few other areas smooth as well. Here it is sanded and ready to go!

Kraylix-sanding 003

At this point the cabinet is ready for paint! It’s looking like I’m going to hire that part out, as I don’t really have a great place to do it and I like the idea of using automotive paint (which I definitely can’t do at home) since it’s so durable. The most time consuming part is prep, though, and since I’ve done that I should be able to have it painted fairly affordably.

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Kraylix Assembly – Day 2

Today I finished assembly of the cabinet. The glue around the arch had set overnight, so I removed the clamps and took a look at the results – pretty good! Some filler will be needed to seamlessly blend the top arch to the side arms, but that should be a fairly straightforward task.

Kraylix-assembly-d2 005

Next up was to install the screen bezel – it is secured with six wood screws, three on each side. In general I have found the Kraylix kit to be extremely sturdy and well built, but this is one area where I feel some extra bracing could improve the design further. The screen bezel is fairly thin and somewhat flexible, and the design leaves it unsupported across the top and bottom. Once installed I could definitely flex it quite a bit with relatively little force. Since the panels above and below don’t form a 90-degree angle with it, though, how best to add some bracing? You could fabricate a wooden piece built to just the right angle, but I came up with something way easier – I used some small hinges from the hardware store. The hinge conforms to the angle needed, but nevertheless adds the rigidity needed to prevent the screen bezel from flexing away from the support piece that runs along its edge. Note the light shining through between the two pieces, as they don’t even touch each other! That’s very much intentional as this edge won’t be visible in the completed machine.Kraylix-assembly-d2 001

Perhaps the most complex part of the kit is the control panel, but thankfully it comes pre-assembled and pretty much ready to go! I removed the top and bottom panels to take a look inside – all the necessary routing to mount joysticks and buttons has been already done by Kray. The only thing the control panel will need is a bit of sanding and lots of dust removal before paint. Here’s the view of the upside-down panel, where you can see the inner routed channels for the controls.Kraylix-assembly-d2 002

Note that in addition to the 8+8+2 top-side buttons, there is room for 4 more buttons on the bottom. What you can’t see on the photo is that there is also room for side-mounted buttons, two on each side. I can’t imagine running out of buttons on this panel…

One other task I did today was to test-fit my screen to the cabinet. No photos, unfortunately, as I was too busy holding the screen up to take a photo. The kit comes with a wood mounting bracket with holes pre-cut to some popular monitor/TV mounting patterns. For this project I’m using a Vizio D32-D1 and I’m happy to report it fit the cabinet just fine. It also worked great with the kit’s mounting bracket which didn’t require any modifications whatsoever. Once I was satisfied the screen would work out, I removed it and stashed it away in a safe place – it won’t go back into the cabinet until after painting is done.

Here’s a photo of the state of things after day 2 – rough assembly complete! Kraylix-assembly-d2 004

Next up will be patching with filler and sanding to get ready for paint! It’s remarkable how easy the kit was to assemble and how quickly it went together. At this point I can wholeheartedly recommend the kit without any hesitation if you’re interested in such a design – it really is a nice piece of work. See the Kraylix Arcade website for it and other variations Kray sells.

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Kraylix Assembly – Day 1

Today I started putting together the Kraylix kit! But before the first screw even goes in, it’s time for my first mod.

One of the nice things about building a kit vs buying a pre-made cabinet is it’s quite easy to customize it to your needs. The Kraylix V4 2-player comes standard with holes for two 4″ speakers – That’s certainly fine for midrange and treble, but what about bass? I definitely think something a bit bigger is in order to get good full-range sound… So I started planning for the addition of a woofer to the cabinet. I happened to have a spare woofer from a subwoofer box whose amp overheated and fried itself dead – the woofer cone was fine, though, so this is a good way to re-use it! I cut a hole on the front panel and test fit the woofer – perfect fit!

Kraylix-assembly 001

Okay, I admit, I cheated a bit – I took this panel to a local car audio shop and they cut the hole for me. I don’t have a router and wanted a super clean cut circle… Car audio shops do this all the time since they commonly build speaker enclosures, so they did it for me – took them a whole minute and a half! The woofer as seen above may look small, but it’s an 8″ diameter speaker. The hole on the right is for a coin door, in case you’re curious.

Much easier to cut this hole before the panel built into the cabinet, of course. That was the next step, building the bottom of the cabinet. It went together super easily, pretty much like any flat-pack furniture would. Kray uses a combination of wood screws and locking cam-on-dowels. Here’s the bottom of the cabinet assembled – it took about 30 minutes of work at most: Kraylix-assembly 002

Next the tall side arms are installed and affixed using nuts and bolts (for easy disassembly later if needed), and the top arch is installed using wood screws and glue (hence the clamps). The glue will set overnight, so that’s it for today. Boy, this is starting to look like a real arcade game! Pretty cool!Kraylix-assembly 003

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