Quoted from davegauth:DIY Round 7....
Let's talk amplifiers.. The second Whoooaaa moment...
This is an area that scares many people and probably one of the biggest roadblocks that stops people from going any further in the DIY sound upgrade area. What amplifier do I use, how do I wire it, where do I connect it, and so on...
I covered the stock class D amplifier chips built into the Spike board a couple pages back, with its specs and limitations. Now it's time to upgrade that stock amplifier in order to get the most out of your pinball sound system. Updated the stock amplifier can net you 2x,3x, even 4x more power going to your speakers, and it's easy and inexpensive to do.
Let's demystify some things...
The first question usually is - What amplifier do I get, will it work with my machine? The answer is as simple as - Any, and Yes.
Any amplifier will work, however; you are most likely going to settle into a class D mini amplifier that will cost around $30-$125ish. If you are spending more for an amplifier you are going beyond the upper limits of "Bang for the Buck" performance levels. Class D simply refers to the type of amplifier, sometimes it's called Digital Amplifier - though it's incorrect as that is not what the D stands for. All you need to know about class D amplifiers is they based off amplifier micro chips, they are inexpensive to make, small in size and are very efficient turning most of their input power into output power with little heat generation. The majority of consumer level amplifiers sold in big box stores like Best Buy etc. are now Class D. Almost all blue tooth speakers are Class D. Almost all bookshelf speakers are Class D. They are everywhere. Mini-amplifiers are simply just the parts of the electronics that are associated with amplifying the incoming signal(RCA) and sending out an amplified signal that powers the speakers. When you strip all the extra stuff off of a bookshelf stereo - CD Player, speakers, casing, display, buttons etc. You are left with just the amplifier electronics allowing mini amps to be small and inexpensive.
Will it work with my machine? YES it will work with ANY machine. There is no mystery here, no dark secret, no rocket science or engineering needed. If you can get an audio signal out of your machine, then you can use any amplifier on any machine you want. Think of it this way, If you purchase a nice bookshelf stereo for your home, do you wonder if it will be compatible with your phones Bluetooth? Probably not - you assume that as long as the Bluetooth connects to the stereo then the phone will provide the necessary signal to the stereo and the stereo will simply do it's thing. Your pinball machine is no different. You are basically turning your pinball machine into a stand alone stereo. Yes the speakers are still mounted in the cabinet, and your amplifier will live somewhere in or on the machine. But they will be completely separate systems, the only link between them will be the sound signal connecting the pin to your new stereo.
Second question often asked - how do I wire it all up? It's easier than you think, so don't ever complicate this to start.
Your amplifier will need 3 things. An Audio signal, speaker wires, and a power source.
- Audio signal, we covered this pretty good a few pages back. In summary, an adapter of some kind will create the RCA level input you need for the amplifier.
- Speaker wires, the stock speaker wires used in your pin will just be disconnected at the speakers and not used anymore. It makes little sense to try re-using the stock wires. They are too small(gauge wise) and too short(length wise) to bother with them. Simply disconnect them, leave them in the pin to hook back up again later, or remove them to keep everything super clean. I'm pretty sure everyone here has purchased a roll of speaker wire and wired speakers before. This will be no different, positive to positive - negative to negative, left - Right - sub. easy stuff. As far as wire size, 18-16ga will do just fine(I use 16ga).
- Power supply. Ok - I admit this is the one that throws everyone for a loop. BUT don't hurt your brain and overthink this one. Eat the elephant one bite at a time and don't get to far ahead of yourself. The most important thing here is how much power do you need and NOT where do I plug it in. This part gets a little technical, because depending on the amplifier you choose to go with, you will have to have an understanding of how to figure out how much power you need and hence the size of the power supply. Fist off - keep in mind power in equals power out.(It's more technical than that, but for simplicity) An amplifier can not put more power than it takes in. So if you have an amplifier that says it can do 50 watts x 2 for the backbox speakers and 100 watts for the subwoofer. Then that adds up to 200 total watts of output. Meaning you will need a power supply that will give you 200 watts of input power. All power supplies will have specs written on them. Output power is generally indicated in Volts and Amps. (Think of a water pipe, volts being water pressure and amps being size of the pipe, and watts being how much total gallons of water made it through the pipe) The formula is simple: Volts x Amps = Watts. In the example above, if you need 200 watts and say your amplifier calls for a 12 volt input. Then you can do the back math and determine that your power will have to be 12volts x 16.7amps = 200 watts. If you were using a mini-amplifier with a requirement of 24 volts input then it would be 24volts x 8.4amps = 200 watts. Easy right? No matter which type of power supply you choose to use, a plug and play power brick, or metal cased power supply with terminal lugs - the math will be the same.
Curve ball time...... There are a couple rules of thumb when choosing a power supply.
- Amplifiers are stupid optimistic about their ratings claims. In the case above that amplifier you determined needed 200 watts. Really only needs about 60-70% of that to run optimally. Anything beyond that will usually push the limits of the amp into distortion, clipping, and noise that isn't pleasant. That 1984 Hugo says it can do 85 on the highway, but you are best to stick with 50mph for best results. There is much more that goes into this, but as a general rule of thumb plan for about 50-75% of capacity and you will be just fine.
- Voltage matters. Amplifiers will put out the most wattage when the voltage matches the higher end of their specifications. This is super technical, I'll link to a video if you want to geek out. But in general a simple Class D amplifier is limited by the voltage it receives. The voltage determines the rails, or parameters/limits the amplifier can amplify in. So if you have a mini amp that says it can operate from 12 - 26 volts, you will get significantly more output running it with a 24 volt power supply versus sticking a 12volt supply on it. Again, super technical - just remember run closer to the upper limits of the input voltage.
For the geek in you -
- There are other considerations and technical things that can come up. But for now let's not over think this, as it's really pretty easy.
And lastely, Where do I connect the amplifier power to in the machine? This is easy - and one step at a time, keep it simple.
- Start by wiring it directly to the wall with a separate plug. This will work just fine. Then with everything working you can think about how you want to connect it to power inside the pin and make it a 1 button turn on. There are a few ways to wire it into the pin for 1 button turn on. However; the general consensus is not to tap any power off the boards. Yes, it can be done - but it is simply not worth doing it. It's best to keep the boards completely isolated from your amplifier wiring and avoid any possibility of board issues later. AC Power for your new amp can simply be tapped in right after the main power switch in the backbox.
And there you have it - Amplifiers demystified. Hopefully - maybe - just a little bit.....
Hope this helps, feel free to add to this or correct/highlight any helpful thought you may have.
Next writeup - we'll cover the types of amps that can be used and pro's and con's etc.
Austin, TX
