powering PC speakers in a MAME cabinet

[krick]

I'm still in the parts gathering phase of my MAME cab conversion.

I was at Target last night and I picked up a set of crappy Labtec speakers for $15 with intentions of hacking them up and using the amplifier to drive the two speakers that are already in my cabinet.

However, I had intended to power the amp using the 5v or 12v that power supply in my computer.  It turns out that the speakers have a power "brick" that puts out 9.4V at 400mA.  Grrr...

I know that I could probably rig up something using a linear voltage regulator to knock the 12V  down to something close, but I'm far too lazy for that.


So after a little digging, I found some crappy internal speakers that are powered off of the PC's 12v  power supply.  I think these will hack up nicely.

What do ya guys think?

http://www.tigerdirect.com/applications/searchtools/item-Details.asp?EdpNo=495587&sku=C375-1001

[krick]

JUst found the same thing cheaper at CompUSA.com...
http://www.compusa.com/products/product_info.asp?product_code=50277791&pfp=SEARCH

[krick]

and even more choices...

http://www.pricegrabber.com/search_attrib.php?page_id=77&form_keyword=bay&ut=442c23100905a4fd

[Nailz]

http://www.oscarcontrols.com/speaker/index.shtml

[crashwg]

Why not just hook up the power "brick"?

[krick]

Why not just hook up the power "brick"?

Because that would require me to put a power strip inside my cab.
I'm hoping to avoid that if possible.

[CthulhuLuke]

I HIGHLY suggest Oscar's method, just make sure the speakers you get are stereo speakers, well I mean you can get a mono set of speakers, but it sounds much clearer when you have a stereo output.  It hooks up exactly the same as a mono, but it's stereo ya know.  Usually a stereo set of speakers is only 5 dollars more, I got my set that came w/ a subwoofer for $15.99.  Cyber Acoustics at Fred Meyer, works like a charm.

[krick]

I think everyone is missing the pont of my post.  I intend to use the oscar controls method.  The only difference is that I want to ditch the power brick and power them off of the PC power supply.

I just wanted to run my plan past a few more sets of eyes to see if there was anything I was overlooking.  Ya know, maybe someone else had tried this before and found a problem with it that I didn't consider.

[Macros]

Check out my post at the end of this thread.

http://www.arcadecontrols.org/yabbse/index.php?board=5;action=display;threadid=13387

[SirPeale]

Just found out how to reference specific posts, wanted to show you all.

http://www.arcadecontrols.org/yabbse/index.php?board=5;action=display;threadid=13387#msg117358

Note the #msg and the message number at the end of the URL.

[krick]

Check out my post at the end of this thread.

http://www.arcadecontrols.org/yabbse/index.php?board=5;action=display;threadid=13387

That would definitely have done the trick.  I chickened out and ordered the drive bay audio unit at the top of this thread.  Buy.com ended up having the best price.  I just returned the Labtec speakers to Target.

Though I did do a little digging and found this page that sells pre made 9v regulator circuits as a kit for $10.99 or fully assembled for $20...
http://www.eidusa.com/Electronics_Kits_9_Voltage_Reg.htm


Here's a few more links to more complex voltage regulator units...

http://www.circuit-innovations.co.uk/317.html

http://www.electronics123.com/amazon/catalogue/c3-3-8.htm

[krick]

Ok, I got the bay speaker unit yesterday, hacked it and wired it up last night.  Suprise...  it sucks.

The power output is woefully inadequate.  The internal speakers are an amazing 0.5 watts each.  So you can imagine the volume it's capable of delivering to a pair of 8 watt cabinet speakers.  And as a final insult, they pick up noise from the 12V line in my computer.  In particular, when my CD-ROM drive is spinning, you cain hear a faint whine in the speakers.

So back to the drawing board.

I've come up with another idea... USB powered speakers.

http://www.pricegrabber.com/search_getprod.php/masterid=584110/
http://www.partshelf.com/bensp868usbp.html
http://baber.com/baber/speakers/benwin_sp691.htm


Any thoughts?

[AlexC]

I thought about doing it that way but it was just going to be too much trouble, I just went with these instead :
http://www.amazon.com/exec/obidos/tg/detail/-/B0000AZJZB/ref=ase_slickdeals/103-7291015-1213447?v=glance&s=electronics
They are awesome speakers for the price and have the volume control box that you can run to the outside of the cab.

[1Spoon]

Why don

[krick]

Why don

[ashardin]

USB speakers will be woefully underpowered anyway.

To get the results you want, I'm afraid you are going to have to bite the bullet and find a way to get power to those speakers.

Another idea is to switch to a 12 volt speaker solution.  Car audio is 12 volts, you could get a small power booster or 20wx2 car amp and run it off of a computer power supply.  I still think you may experience noise problems from this (due to the fan inducing a whine).

You might just want to find a way to get power to amplified speakers.

[krick]

I just found this at Happ Controls...

http://www.happcontrols.com/amusement/jukebox/495140200k.htm

It runs off a 12VDC and I think it could be powered off of a PC power supply.

It's a little expensive (about $60) but would make for a really professional installation...

[krick]

Cool!   They have the amplifer by itself...

http://www.happcontrols.com/amusement/jukebox/495140100.htm

$41.35 with enclosure
$32.65 without enclosure

[Xiaou2]

 according to the specs... its max power is only a mere 8 watts.   I think most cheapie boom boxes have more power in them.

  you may want to reconsider...

  Imop... game sound is pretty important.  Clear, clean, deep bass, powerfull... : )  I may pop a surroud system in mine... not sure yet...

[krick]

 according to the specs... its max power is only a mere 8 watts.

I did consider that but I want to keep my cabinet as close to original as possible.  I want to use normal cabinet speakers and I want it to sound as close as possible to the real thing. Cabinet speakers are usually less than 10 watts.  Some, like the 4x4 ones I'm getting from Bob Roberts, are only 5 watts.  So, hey, it might sound crappy but the real thing sounded crappy too.  I think it's a more "accurate" emulation of the whole arcade experience.


I can always "upgrade" the sound system later if I decide I want something better and more powerful.  If I did, I'd probably go the 12v car audio amp route and use car audio speakers.


...
Krick

[Sylentwulf]

Aren't car amps and speakers powered off a straight 12V from a car battery? Couldn't you use the same in an arcade cabinet off the 12V line?

[alank2]

I too had many issues with the audio, and here is my audio story!

I first ordered a 20W amplifier from www.canakit.com, a UK194, which costs $14.96 assembled plus shipping.  They make a smaller UK153 you might consider (5W).  My speaker came with the cabinet and is single 6x9, 8 ohms, shielded.  You can get the speaker at www.mikesarcade.com.

Because I went from stereo (output from sound card) to mono (one speaker), I used a 10k resistor on the left and right audio line.  So you would have the Left line then a 10k resistor then the right line and another 10k resistor, then the 10k resistors hookup together and become your mono sound input.  These resistors keep the audio signal from feeding too much current from left to right or vice versa when the signals are not identical.  I then added a 47k resistor from the joined 10k's to the input signal on the amplifer to cut down the volume just a little more.  Someone also suggested connecting a 15k resistor to ground from the 2 10k resistors to prevent more signal loss.  I must admit that I don't understand what the 15k does, but things sounded better with it so I kept it.

I did have some trouble with potentiometers.  I had the idea of mounting the volume switch through the cabinet, and I needed a new potentiometer to do this.  I tried various ones, but couldn't get the one I needed (easily or cheaply) which was a 20K audio taper.  In the end, I mounted the volume in the coin door instead of on the top of the cabinet as I hoped.

I did start with the PC power only to also find it has way way too much noise to be useful.  Use a good quality power brick.  Also add a large enough capacitor to help eliminate any noise across the power leads.  Also, items like the fluorescent light will cause noise when flicking on and off.  I handled this issue in one way so far by replacing the lights of america fluorescent light with an electronic ballast (www.fulham.com) and now no more flicker, it just comes on when I turn the cab on.  There is still a noise in the amp when the light turns on, but at least it isn't on/off/on/off/off/on/off/on with respective noises.  I have heard that putting a line filter on the fluorescent light will also help the situation.  Mike at mikesarcade also has these.  I am going to add one of these to the fluorescent light as well.

Make sure you use SHIELDED cable and that you connect the jacket/ground wire to ground.  This will greatly reduce the noise in the audio signal.  It is also a good idea to ground the heat sink on the amp itself.

In the end, I tore my UK194 apart and rebuilt a sound circuit based on one TDA2003 IC chip instead of the 2 it had.  This resulted in much less current use (50ma instead of 200ma), but only 10W amplification.  10W will still more than enough for what I needed.  I did this hoping to improve my potentiometer volume situation, but knowing what I know now, I would have just left the original UK193 intact and used it.

If you want a single kit with a TDA2003 amplifier, velleman makes one K4001 at www.vellemanusa.com.

Hope this helps!

Alan

[southpaw13]

Hello, I used a 30 watt RMS car audio amp and it worked great!  I turned the power gain down and had more than enough power.  No noise problems...

[krick]

I did start with the PC power only to also find it has way way too much noise to be useful.  Use a good quality power brick.  Also add a large enough capacitor to help eliminate any noise across the power leads.

I found this dc power supply noise filter circuit in a book I have called "Do-it-yourself Projects for Guitarists" by Craig Anderton.  He recommends adding this circuit to any power bricks that are adding hum to an audio circuit.  It's a great little book.  In addition to useful circuits like the one pictured here, there's plans for a DC power supply and a small 8 watt amp that would be perfect for driving cab speakers.

[krick]

I just wanted to give an update.  I'm still using the hacked "bay" speaker unit.  After using it a while, it's really not that bad.  Yes, the 0.75 watts per channel is really weak and the intermittent power supply noise isn't wonderful.  But over all, it's actually useable, at least until I can settle on something better.

I may try to add the power filter circuit that I posted above to see if it helps any with the DC noise.

I've got a really cheap set of USB powered speakers on the way.  They're a whopping 2 watts per channel but I'm sure they'll sound far better than what I've got now.

...
Krick

[Wienerdog]

Holy smokes that was too much work...

Are you sure you aren't trying to solve the problem with the most complicated solution possible?

It sounds like the problem is that computer speakers are powered by a "brick" which needs an AC outlet, but you don't want to run a power strip into your cab.  Are you sure you didn't dismiss the "cut the cable" option too soon?  Is there another reason you don't want to use the supplied power supply?  

You have an AC line running into your cab.  Split that line before it goes to the existing cab power supply and run it to a power strip.  Plug your speaker power supply into the power strip.  I think the common problem with audio is that most of us want more than an 8watt output.  Since you are not bound by those desires, go with the easy solution and save some money on the experiments.

[PedroSilva]

Why don't you hack some cheap powered speakers ... it's easyer, cheaper, faster and normally it works fine ...  

[krick]

Ok, I got my USB powered speakers today.  This is basically what they looked like before...



...and this is what they looked like after...



I temporarily connected my cab speakers through the headphone jack (which is electrically equivalent to connecting them to the regular solder points) to see what the little 2 Watt per channel amplifier could do and they sound pretty damn good if you ask me.

I don't detect any noise from the PC power supply and the volume seems to be more than adequate for my little 5 watt cabinet speakers that I bought from Bob Roberts... http://www.therealbobroberts.com/

Now I just need to connect my new speaker wire harness and figure out a way to mount the amplifier board in the cabinet.  I'm thinking about slapping a piece of sticky backed velcro on it and mounting it to the wall of my cab in a place that I can reach from the coin door.  Either that or I'll drill some small holes in the corners of the board and try to mount it with screws and standoffs a la J-PAC.

All in all, I'm very happy with the way they turned out.

[Brewser]

What have you guys done about the volume controls?

[Silverwind]

I bought a sherwood receiver on sale at outpost.com for 79.99.  A little robust but eh what the heck.  Real easy connection to my PC through the sound card digital output.

I had a pair of 6.5" component speakers laying around that I'm going to use.