At the end of the day, alot of arcade mods just involve really basic electronics. When I first looked at Stereo modding my Astro City, I figured that I would have to do some really complicated things to make it happen – turns out that it’s actually really god damn simple.
Modifying the Astro City for Stereo Wiring
When you start looking at games for your cabinet that allow for stereo, you generally start looking at options for a stereo amp as well (you should, because the difference is massive). A stereo amp doesn’t have to be a complicated option like an expensive Capcom Q-Sound, or some other shitty eBay amp. Literally all you have to do is buy a set of cheap PC speakers – 2.1 (left/right – subwoofer) – that is the amplifier you want. It gives you a tonne of options, not to mention a small subwoofer for a bit of bass inside the cabinet. Also it’s cheaper (but requires it’s own wall power plug too).
After looking at how the Astro was wired in relation to the stock Sega power supply (with the volume pot, but no amp), I figured out that the easiest way would be to simply separate the speakers from the wiring equation. Make them their own entity. That way you can just plug in whatever damn output you want, including the original Sega dual mono (yes that’s right, from the Sega PSU comes DUAL MONO). Observe:
I terminated the speaker connections inside the Control Panel and soldered them to RCA jacks (I used White/Yellow because that’s all I had, but I mean, as long as you keep one colour in conjunction with conventional stereo wiring, who cares). This makes them a simple input – kind of disconnected from the rest of the cabinet wiring. Connected in this picture, is the 2.1 output from a cheap set of Edifier M1360 PC speakers. I made a little plastic bracket to hold the connectors as well. It’s basically just wedged there, but because of short wire lengths and tape, it’s not really going anywhere.
By separating the speakers this way, you can literally just run RCA cables from whatever to inside the control panel and switch them over at will. This allows you to not only retain the original Sega DUAL MONO output if you want it, but it also allows you to add a simple 2.1 PC speaker set to the cabinet VERY easily. Inside the Astro City Control Panel, the audio wiring is connected to cabinets original wiring loom in a 4-pin connector. It is the first connector on the left with the following wiring:
||Pink w/ Blue Stripe
||Grey w/ Blue Stripe
||Pink w/ No Stripe
||Grey w/ No Stripe
The Sega wiring loom comes right up to that plug inside the cabinet, and on the front side of the connector is the speaker connection. So if you think about it, you are essentially just changing that 4-pin connector to dual RCA inputs (while retaining the option for exactly the same connectivity as before the mod). So what you want to do is split the wiring from the plug at the front of the connector, and solder RCA output plugs to it. Like so:
What I’m holding is the 4-pin plug, soldered to a set of RCA outputs (red/white). I just butchered a set of standard stereo cables I had laying around. I also used white/red tape to mark the correct sides on my soldering as well. In this picture, the Sega PSU Dual Mono is plugged into an extension cable that goes to a HIGH to LOW Line Converter inside the cabinet, but I’ll get to that a bit later. But before I had that setup, I just had the Dual Mono plugged into my speaker inputs (which makes it functionally the exact same connection as the original wiring when you started).
I know that some people think modifying the original Sega loom is sacrilege, but it’s clearly the best way to go about this mod without too many issues. Not to mention, my way is easy enough to reconnect the old fashioned way if you’re a bit anal retentive, or you’re selling your Astro to someone who is.
So what’s next? You’ve made your speakers a separated Left and Right capable entity now, with the option to just plug your JAMMA audio straight back in as normal. Great! At this point, I looked at what I should do with the speakers and opened the back of the cabinet.
The speakers inside the Astro City are an irritating 3 Inch, 4 ohm and amusingly unshielded. Unshielded speakers in a cabinet with a CRT monitor? Nice one Sega.
These are the speakers I removed from my cabinet sitting on my work bench. Being Sega branded does not make them any good, I can assure you.
Finding replacements for these is tough. A thread on Arcade Otaku suggested some Creative Soundworks SBS52 PC speakers because they are a simple drop in replacement, but around my place I discovered I had the remnants of a shitty LG Home Theatre system with a bunch of tiny little satellite speakers. Imagine my face when I opened one up and the speakers were exactly 3″ (but 6ohm – not that I really think that matters given the low power you’re working with here, realistically). The best part about them? Magnetic shielding (you can tell because they have a metal cover on the back your Sega ones don’t).
Changing these to LG speakers was an INSTANT and remarkable improvement over the terrible Sega ones. That was before I’d even amp’d them.
It pays to get creative and scrounge around to find speakers of this size. Otherwise I guess you could experiment with making templates for slightly larger 4″ car speakers or something like that, but I just swapped in the LGs after taking them out of the cases (the Satellite’s have the model number: LHS-D6246T if you want to look for them or something – 6ohm, max power 50w).
One small change I did have to make to cabinet wiring at that point was that the positive terminal speaker plugs were too small – I just changed them for wider connectors I had – you could probably just get away with wrapping the wire around the terminal or something if you had to, but in the interests of doing it properly, you would want to change them to wider connectors. Be careful not to strip too much wire away either because their isn’t really much play there.
I had a choice between weaker but cheaper Logitech LS21’s, or the the Edifier M1360 2.1’s for a little more. I decided on these.
When looking at amps for your cabinet, you need to figure out a few things. How you’re going to power them – whether you want a system that can just be piggybacked off the JAMMA connector (putting more load on the Astro’s already fairly weak Power Supply), or whether you will just plug them into the wall (a much easier option). But that leads to another question. How do you get a power cable inside/outside the cabinet? Illegally sever an extension cord so you can pipe it inside the cabinet without external modification, and resolder it yourself? Get an electrician? Or some use some other already existing hole inside the cabinet to pipe it in/out?
In Australia (and most countries), carrying out electrical work requires a LICENSED electrician. Don’t perform any work on power cables unless you are an electrician, or are planning to have it checked over by one. It’s illegal, and no one likes a house fire or electrocution.
Anyway, with that warning out of the way, I got an extension cord piped in so I could just plug the damn thing in without any hassles. Another thing I had to weigh up with choosing the Edifier system was that I would not have a Bass Adjustment like some other PC speakers in this price range have. That’s a decision you have to make I guess. I haven’t missed it, put it that way.
In buying these too, you basically are just throwing the satellite speakers straight out. You don’t need them at all, you just want the amp/sub/volume controls anyway. The M1360s put out 4ohm’s through the satellites at 2 x 2w. That’s right, low power. I mean, someone feel free to correct me if you like but I honestly think the ohm rating means shit at this level of power. As long as your speakers and amp choice are reasonably close together ohm wise, it’s not going to matter in this case. Worst that could happen I guess is that you’ll blow out your cheap ass PC speaker amp. Boohoo.
Anyway, even though the website says it’s as low as this, the sound output in my case has been excellent. It is miles ahead of the standard JAMMA mono in quality. In terms of placement inside the cabinet, there is a convenient spot right behind the cash box!
Please forgive the average photography, but you get the idea. It goes nicely right behind your game board and cash board in the back right corner of the cabinet. Initially I had the volume control where you see it here, but I actually figured it works much better literally right inside the main door – behind the gameboard.
Now that’s all powered up, let’s talk 2.1 wiring. Here’s a convenient graphical representation of what I’ve done:
(Click for full size)
For that guide I actually modified another persons guide that I found (I think it was on Arcade Otaku as well), though unfortunately I don’t have the link to credit. It basically sums up my system in one hit. Depending on which system you choose for your Astro City, you might need a couple of RCA -> 3.5′ (headphone socket) adapters and that kind of thing, it’s very much setup dependent. I’ll leave it up to you to figure out what conversions you need to make to wire it all up.
In this case, the audio input on the Edifier speakers needed to be a 3.5mm plug, so I used one of those and hooked an RCA adapter on the end:
I know I know, average photos. I basically just double side taped the 3.5mm -> RCA connector right on that strip between the main door/cash door/coin mech door. From there, you can either plug in whatever stereo game (CPS2, Konami GX, Neo-geo, whatever) you like and it’ll go to the Edifier amp.
So by now, you should be experiencing awesome stereo sound from games with Line-Level audio out! Awesome! This brings me onto a new point:
Adapting JAMMA Mono for output through your new 2.1 Stereo System
Easy. With this:
A simple High to Low Line Converter from our friends on eBay or your local electronics shop. These are generally used for car sound applications for shitty stereos with no RCA pre-outs, but in our case it’s for arcade gaming goodness. Mine came from eBay with bare wires for inputs, and RCA outs for… well.. output. To the bare wires I soldered yet more RCA inputs. Guess where I put those? That’s right, in the control panel. You know what else I plugged in from there? The Sega DUAL MONO plugs I made earlier.
So now your amplified JAMMA audio is plugged into a line level converter with RCA outputs. Now you can plug those RCA outputs, into the spot I pointed out previously, and you’re ready to rock and roll with your formerly baseless and flat old Mono games. The difference is phenomenal.
In terms of calibration – make sure you start with both the game volume, and the Sega Volume pots on basically a low or default volume. If it’s too high, you’ll not only blow the Line Adapter, you may damage the audio in whatever game you have running. The whole point of the Line Converter is to take the pressure off the game, and put it on the Stereo Amplifier. If you decide to forgo the Line Converter and try plugging your Dual Mono straight into the new stereo system, you may damage the game quickly. A sign of audio that’s too high through the adapter is crackling or popping.
Think about it – JAMMA audio: Amplified. Your stereo amp: Amplified. Amplified + Amplified = BOOM! Don’t risk it. Buy the cheap adapter.
To make life easier on yourself, it’s a good idea to label all of your extensions so you know what’s going on if you need to change something.
From this point on, you pretty much only want to adjust the audio volume from the Edifier volume control. And now that you have the option of both JAMMA audio or Stereo by changing inputs just inside the main door, you don’t even need to worry about getting into the Control Panel as much anymore. Your speakers can be left connected to the Edifier/whatever you chose system full time.
I hope this guide has helped – or at least told you a few things you might not have known about how your Astro City is wired up. This is without a doubt one of the easiest and most rewarding changes you can make to your Astro City and it is very much worthwhile investing some time in.
If there’s anything I haven’t covered here that you feel I might be able to help with, feel free to comment and I’ll get back to you ASAP.