How To

Hey Everyone,

Just wanted to post a quick update.  When I was describing my sound system tuning process to a friend, it occurred to me that this could be a pretty cool little update.   I am going to keep it semi-simple as this can be a wormhole of confusing information.

So here is what is going on.  Whenever you have a very powerful sound system that you hobbled together yourself, it is pretty risky to just tune your subwoofers by ear, especially if the output of your amp is close to the RMS rating of your subwoofers.  You can easily blow up a speaker by sending clipped output signal to them from the amp.

What is a clipped signal?  What does it look like?  For this conversation, we are going to pretend that our sound is a perfect sine wave.  The image below shows our perfect sine wave on the left.  On the right side, you can see that the sine wave is now flattened at the top and bottom.  This is called clipping.

Image credit goes to http://modernmixing.com/

Image credit goes to http://modernmixing.com/

Clipping happens when an audio signal is pushed louder than the amp can handle, so some of the data is cut off from the signal itself.

Now, back to my machine…  What I need to do is make sure that none of the audio signals are clipping on my machine, but still drive the amp and subwoofer as hard as possible.  So here are the high level steps that I took to verify that everything was ok.

  1. I created a sound sample which was a perfect sine wave running at 50hz (50 cycles per second) and set it to be the default music on the Total Annihilation machine.  (see image below)
    50hz
  2. I then disconnected the audio cable from the computer to the subwoofer amp and hooked up my oscilloscope to the output signal from the computer.  This allowed me to physically view the sound wave on my screen, you know, with my eyes.  This is called checking the pre-amp signal (in case you wanted to know).
  3. I then started a game and took a look at the 50hz sound wave that was now playing.  You can see from the image below that the signal is nice and smooth (no clipping).  Yay!
    sine-wave
  4. Next I plugged the computer audio cable back into the subwoofer amp and disconnected the subwoofer.
  5. The next thing I did was turn down the amp gain all the way to 0% (this is important).
  6. The oscilloscope was then hooked up to the high level output of the subwoofer amplifier, just like how the speaker is hooked up.
  7. I started another game to get the 50hz signal playing.
  8. Then I turned the gain amp up slowly until I could start seeing the sine wave.  I kept going until I saw a bit of clipping in the signal and then backed it down slightly under that limit.  This is simply called the amplifier signal (post amplified signal).
  9. Success!  This now has set my amp to it’s maximum clean output and I will not have to worry about blowing the (not cheap) subwoofer in my game***.   ***Yes, I could technically still blow it, but we do not have to talk about that now…
    20160622_192517

OK, OK, so there are a TON of technical details and nuances that I purposely left out of this post as it would have made it not fun to read.

Well, that is about it.  You now know how to properly check your audio amps for clipping.  All you need is some time and an oscilloscope.  🙂  Also, the sound system has never sounded so good in Total Annihilation.

See you guys/gals at Expo 2016!

Hey Everyone,

After populating my V1 playfield and testing a few things out, I discovered that my upper right kickback design was not very smooth and I just could not live with the design as it seemed amateur to me.  I ended up replacing the upper right side of the design with some straight inline drops with a scoop behind them.  I am going to do some really cool ball locking tricks with this setup and it will be much better than the original design.  Below is a rendering of the upper section of the V2 playfield that I updated.

A

So on a separate note, I have gotten a bunch of questions on how the hell I am milling a full sized playfield on an X-Carve that is only capable of doing 31″ x 31″.  The process is not that difficult.  Here are the high level steps that I perform to get my playfields cut.

Step 1: Export the full DXF file of my playfield from SolidWorks.  You will notice in the 2 images below there are 2 little lines sticking out of the right and left side of the playfield.  These will be referenced in the next few steps.

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Step 2: Import the full DXF into my CAM program and delete all the lines and artifacts ABOVE the 2 guide lines.  I then program the CAM and save as “Playfield Bottom”.

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Step 3: Import the full DXF again to a new document and delete all the lines and artifacts BELOW the guide lines.  I then program the CAM and save as “Playfield Top”.

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Step 4: It is important to make sure that the X (left/right) axis is the same for both the top and bottom playfield.  I ensure this happens by setting my X axis to the tip of the left guide line.  This will ensure that the left and right positioning of the 2 cuts are parallel.

Step 5: Start cutting the bottom part of the playfield and return the machine to X0 Y0 when complete.

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Step 6: Once the bottom part of the playfield is cut, I unlock and slide the stock down and align the tip of the left guide line to the center of the end mill bit.  Once I am happy with the Y alignment, I lock the stock back in place.  I then proceed to cut the top part of the playfield without resetting my X or Y axis in the software.  The machine will pick up where it left off and hopefully continue like it was all cut at once.  It is not perfect every single time, but it is damn close.

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Step 7: Let the machine continue and do not set your beer by the Emergency Stop button.

Hey Everyone,

So I have been getting a few questions about how to properly connect an LED sign to my tournament software.  It is actually pretty simple and I will walk you through it below.

Supported Displays:

First things first, let’s talk about supported displays.  Currently, I have only tested the software with my BetaBrite 213C and my Alpha 220C.  These are some of the most common signs you can find that are affordable.  The BetaBrite signs also came included in the Tournament TOPS Kits from Stern Pinball.  I plan on testing other types and brands very soon.

Display Connection:

BetaBrite Connection Info2

This diagram illustrates the display connection to your PC

These signs use a serial (aka. RS-232 or DB9) connection to your PC.  This type of connection is now very uncommon and is most likely not included on that nice new laptop you bought.  Don’t worry though, many products still use this protocol and there are USB to Serial Adapters available for cheap.  I would recommend getting a USB to Serial adapter with the FTDI Chipset as I have not tested any other type.  If you are lucky enough to have a serial connection on your PC then this is not a problem.  I still like to use the USB to Serial adapter since it will also extend the range of the cable that came with your display.

Cable 1

BetaBrite Serial Display Cable

Speaking of which, you should have received a cable with your display that has a serial connection on one end and a network type plug on the other.  If you do not have this cable, don’t worry as they are inexpensive and can be found on eBay.

Once you have all the necessary cables you will need to hook them together and power up the display.

Configuration:

Configuring the sign to work with the software is probably the easiest part.  The one thing you will need to know is what “COM Port” number that your serial connection is set to.  This is a whole number that is usually under 10.  You can find this number by going to your control panel in windows and selecting Device Manager.  Your serial port will be listed under the “Ports” section and have the COM Port displayed in the title.

Once you have this port number, you can now open up the Tournament Manager application.  At this point be sure that your display is connected properly and powered on.  Click on the options tab and then click on the BetaBrite Options tab.  First select the COM port for your serial connection and then check the “Primary Display Output Enabled” checkbox.

Your display should show the test message!  From here you can setup a “Standby” message that will display on the BetaBrite while you are setting up the tournament.  You can use it to say when the tournament is starting and how much it costs to enter or whatever you want.  🙂

References:

BetaBrite Cables on eBay

USB to Serial Cables on Amazon

As always, let me know if you have any questions.

–Scott