(Topic ID: 81398)

Adding an amp for a subwoofer

By djb_rh

10 years ago


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#1 10 years ago

In this post:

http://pinside.com/pinball/forum/topic/psw10-amp-only-mod-for-tron-le

I detailed how I removed the amplifier section of a PSW10 and added it INTERNALLY to my Tron LE and connected it to the Flipper Fidelity subwoofer I had already installed in the cabinet. That works very well, but costs about $70-90 depending on when you buy the sub.

If you want a cheaper alternative that doesn't cannibalize a PSW10, you can use a car amplifier. I purchased this one:

http://www.amazon.com/Boss-Audio-R1002-2-Channel-Amplifier/dp/B004S50ZB2/ref=sr_1_2

It's $29 shipped if you have Prime. All I did to connect it was make a power cable to connect to the Stern 3 wire accessory plug (remember you have to connect the +12V to both the power input *and* the "remote" input to cause the amplifier to turn on). Then unplug the subwoofer and make a cable that will connect to the wires you unplugged and go to a single RCA jack. I tried going to the speaker level inputs on the car amp (that's what I used on the PSW10), but it was expecting a much higher level there, apparently. But the RCA plug worked. Then make a cable to connect from the speaker output on the amplifier and go to the speaker in your cabinet.

You will still want to tweak the "input level" knob on the amplifier to taste. You may want to make your cables all long enough you can move the amp to the coin box area to make setting the input level easier, because I found that a setting I liked with the cabinet and coin door open was a tad too much once I put the glass back on and closed the door. Made things rattle. But turning it down just below the rattle level was a big improvement over having no amp on the sub.

Yes, I know, it won't sound "as good" as a PSW-10 sitting on your floor. If you don't mind a PSW-10 on the floor and want the best sound possible, DO THAT. If, however, you don't want an external subwoofer, this is an easy and cheap mod that will get you much better bass out of your pin.

Another note: I would be careful about what car amp you choose. Some are power hogs and may suck too much current from your game power supply. I tested this amp first using a separate power source and current meter, and at normal levels it seemed to bounce between about a half amp and no more than two amps. I do not have any idea how much current it's okay to take from the game power supply in a Stern or otherwise, but this amount appears to work fine. I do believe in this configuration you are unloading the internal game amplifier, so some of this use is offset by less current use in the game's internal amplifier. Note that the PSW-10 solution, either internal -or- external will not have this potential pitfall because it connects to 110VAC, not the internal 12VDC.

--Donnie

#2 10 years ago

It might be easier to get an actual subwoofer amp with a built in crossover and runs on 110v (goes on sale for $28 all the time):

http://www.parts-express.com/dayton-audio-sa25-25w-subwoofer-plate-amplifier--300-782

I'd worry that the Boss amp will end up killing or stressing your 12v supply (or at least blowing the fuse). The Boss has a 7A fuse on it!

#3 10 years ago

Yea. It's not ok to run the car amp on 12v. A 200 watt amp at 12v can draw 16 amps from the circuit. To keep it in safe range, you'd want to keep it around 2amp draw or less. And that's around 25 watts, which is not significantly more than the tda2030 you ready have built into the sound board. The 110v option is way safer and better.

#4 10 years ago

Hmm, I do like that Parts Express subwoofer amp option a lot. Didn't see that one in my poking around. Damn, where were you in the other thread when I was cannibalizing a PSW10?

As for the car amp and load, I know 200W would kill the thing, but that's why you adjust it so you're not doing that. Like I said, I watched it under "full load" for "more than enough" for that little speaker and it was spiking to 2A.

But yeah, I may go back to that Parts Express amp next time it's on sale. Note that for that option it's still a good idea to make yourself a 110V plug that goes to the DBV plug near the coin door to get you switched 110V.

--Donnie

#5 10 years ago
Quoted from djb_rh:

Hmm, I do like that Parts Express subwoofer amp option a lot. Didn't see that one in my poking around. Damn, where were you in the other thread when I was cannibalizing a PSW10?
As for the car amp and load, I know 200W would kill the thing, but that's why you adjust it so you're not doing that. Like I said, I watched it under "full load" for "more than enough" for that little speaker and it was spiking to 2A.
But yeah, I may go back to that Parts Express amp next time it's on sale. Note that for that option it's still a good idea to make yourself a 110V plug that goes to the DBV plug near the coin door to get you switched 110V.
--Donnie

So if it was spiking at 2a, using ohms law, that's spiking at 24 watts. The built in amp in the board handles roughly that. So you aren't benefitting by having an external amp at all.

#6 10 years ago
Quoted from djb_rh:

Damn, where were you in the other thread when I was cannibalizing a PSW10?

lol

#7 10 years ago
Quoted from markmon:

So if it was spiking at 2a, using ohms law, that's spiking at 24 watts. The built in amp in the board handles roughly that. So you aren't benefitting by having an external amp at all.

And if most class AB car amps are about 45% efficient, then where are we at?

#8 10 years ago

Is the amp in the game 25W for just the sub, or everything? Because it's still driving a lot of output to the back box speakers and there's definitely more bass that sounds clearer this way.

--Donnie

1 month later
#9 9 years ago
Quoted from djb_rh:

Is the amp in the game 25W for just the sub, or everything? Because it's still driving a lot of output to the back box speakers and there's definitely more bass that sounds clearer this way.
--Donnie

On tron LE and stern games, there is a dedicated amp for the cabinet sub. One reason it might have sounded better is because you had a volume control on the external amp. If you put an lpad or resistors on the backbox you can basically accomplish the same thing.

#10 9 years ago

I've been playing with little Lepai 2020A+ amplifiers here, PartsExpress forum has a thread about simple modifying for better sound and power, could have some potential. different input coupling caps could change it to bass only.
the stock Lepai might pull 12v at 2A pushing a real 8.3wpc, modded near doubling that. they're a class T amp and about 90% efficient. 8w might not seem like much, but through efficient speakers it can be VERY LOUD, no joke. amps today are insanely over-rated because the FCC allowed them to be rated at 10% distortion for output, the little Lepai (bone stock) can do an honest 8.3wpc before distortion begins hitting 1%, is actually pretty impressive.

if a game has decent stereo sound power to begin with another option would be a goldwood 10" DVC woofer with each voicecoil wired in series to the original speakers. the woofer can do 96 Db on 1w oughtta put some bass in your face pretty good without wiring in a secondary amp. same kind of tactic could be applied to a pair of 6.5" or 8" woofers, the 6's being 33 sq in each roughly 66 for a pair, 8's roughly 50 sq in each for 100, and a single 10 about 78 sq in, so if theres room a pair of 8's could hit a little better than a single 10.

wiring passive in series (low pass filters if desired), a pair of MCM 8's might be a good choice, their specs claiming 94 Db on 1w, 8-ohms, is pretty good for an 8. if factory speakers are 4 ohm you can replace them with 8 ohm and wire them parallel back to 4 ohms shouldnt hurt the amp, could maybe hit a little better. pricewise compared to a "kit" I'm talking dirty, a pair of MCM 8's might be 30 bucks with shipping included:
http://www.amazon.com/MCM-Select-55-2950-Woofer-Surround/dp/B008BWA004/ref=sr_1_5

#11 9 years ago

that little dayton sub plate amp, very nice for sure and a great add-in option, really simplifies things too. the high inputs parallel tap from existing left-right speakers, gain and low freq crossover controls going to two woofer outputs for seperate woofers or a single with dual voicecoils, you really cant go wrong with something like that.
my previous post moreso about doing it passive, works well if added speakers are very efficient, but honestly, the price of low pass filters or crossovers can be approaching the price of that nice little plate amp depending on where you're looking too.. definitely the better! same stuff still applies about a pair of 8's or a DVC 10, whichever theres room to install easier. djb (OP), as to price, that dayton and a 10" goldwood dvc, or a pair of the MCM 8's, is gonna run about 70 bucks for the amp and speaker(s) both, about half the price of most speaker kits I'd looked at.

if a game already has a (powered, not line level) subwoofer output, the speaker itself can maybe get upgraded. efficiency rating (how many Db at 1w 1m) has more meaning than how many watts max it'll put up with. a speaker rated 95 there can sound about twice as loud as one rated 86-87 Db, but that can also depend on what frequencies they're pushing into a speaker to derive the Db output from, can get "fun" when trying to compare em. the goldwood dvc 10 I'd mentioned hitting 96 on a watt is also derived from both coils active parallel, is only 2 ohm load. not a big deal to run them in series to make 8 ohms, it -could- do better than many 8 ohm single coil, dont know for sure.

might be moot point? that dayton plate having 2 outs for woofers might want 2 8's or a dvc 10 (or 12 hehe).
best bang for the buck (95 Db/w/m) I've seen for a single coil 8 ohm 10 is another MCM: http://www.amazon.com/MCM-Audio-Select-55-2951-Surround/dp/B008BWA05O/ref=sr_1_13

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