Arcade cabinet amp wiring

[Add221]

Hi I'm looking for some help,I've just built my first ever mame cabinet and all has gone well but I am an absolute noob when it comes down to certain things,so here goes ,I bought a little amp from http://www.arcadeworlduk.com but don't know how to wire up the power,contacted them and they were of little help, all they said was to power it from a spare molex ,now I know what a molex is but have never done anything like this before.i was wondering if they was some adaptor I could get to power it from the mains(uk) but if not i would appritiate any help,diagrams,vids,etc preferably aimed at 5year olds so I can follow it( I am that dumb with electronics).  Please help

[sandheaver]

The power supply on the computer you're running in the cabinet should be able to provide the power required. 

Is this the one you have?  http://www.arcadeworlduk.com/products/Arcade-Speaker-Amplifier-With-PCB-Feet.html

This product picture should help you, if so: http://www.arcadeworlduk.com/product_images/a/471/sound-amp-2__19475_zoom.jpg 

You'll need a spare connector that would plug into your PC power supply, then run the black & yellow wires to GND & +12V connectors on the bottom right.  Then, on the bottom left you'll put the mono audio in, then on upper right you'll wire those two to your speaker directly.

Does that help?

[Add221]

Yep that's the one,the instructions you have given make it clearer ,thanks

[sandheaver]

Well, if you have further questions, post them here; I'll see them and answer as best I can.

[BobA]

That works well but if you get a hum on your audio then swap the 12V molex connection for a 12V wall wart and you will get rid of the hum.   The wall wart has to be sized to handle your amp.   There is no sure fire way of knowing if you will get a ground loop and therefore a hum until you wire up your particular amp and speakers.

[Add221]

Wall wart?,is that a normal adaptor? If so what should I do just cut the end of? And last question what amp should I use (sorry said I was a bit simple in this area)

[Add221]

When I say amp I mean ampage

[sandheaver]

When I say amp I mean ampage

0.5A would be enough amperage, I imagine.  Depends on the watt rating of the amplifier.  The product page doesn't say, but I think it's safe to assume it's a 5W amplifier, or less.

5W over 12V = 0.42A.  add 20% on for inefficiencies and you get 0.5A.

someone please correct me if I'm wrong on that math.

[kahlid74]

Your equation looks right Sand, but amperage doesn't really matter here, because most Computer power supplies provide plenty of it over the 12v rail.

What you would do is take a spare molex on the PSU from the computer.  Cut the Yellow and black cords from it.  Strip a 1/4" off the end of the yellow and black.  Feed them into the amp where yellow is the 12volt feet and black is the ground.  Then you're all set!  the Computer PSU will do everything else for you.

[sandheaver]

Your equation looks right Sand, but amperage doesn't really matter here, because most Computer power supplies provide plenty of it over the 12v rail.

What you would do is take a spare molex on the PSU from the computer.  Cut the Yellow and black cords from it.  Strip a 1/4" off the end of the yellow and black.  Feed them into the amp where yellow is the 12volt feet and black is the ground.  Then you're all set!  the Computer PSU will do everything else for you.

Agreed, but someone else mentioned there'd be too much noise in a computer PSU.  You don't think so, I take it?

[michelevit]

I can confirm that powering an amp on the same computer powersupply will cause unwanted noise.
Solution...
My cab has two ATX powersupplies, one for the mobo and one for the amplifier.

[sandheaver]

I can confirm that powering an amp on the same computer powersupply will cause unwanted noise.
Solution...
My cab has two ATX powersupplies, one for the mobo and one for the amplifier.

Why don't you just add a filtering capacitor?  That's what they're for and they work very well to combat hum.

[BobA]

The hum is not usually due to ripple on the DC supply.  It is usually due to a ground loop which can be hard to eliminate.

[kahlid74]

Your equation looks right Sand, but amperage doesn't really matter here, because most Computer power supplies provide plenty of it over the 12v rail.

What you would do is take a spare molex on the PSU from the computer.  Cut the Yellow and black cords from it.  Strip a 1/4" off the end of the yellow and black.  Feed them into the amp where yellow is the 12volt feet and black is the ground.  Then you're all set!  the Computer PSU will do everything else for you.

Agreed, but someone else mentioned there'd be too much noise in a computer PSU.  You don't think so, I take it?

So I've been on both sides of this.  I'm not an expert but my experience has been, that with a high end power supply, the noise is canceled for you.  I used an Enermax $79 PSU and there was no noise.  I used a cheap 350 watt PSU that came with a $20 dollar case and the noise was nightmarish.

[Add221]

Right I finally found the time to try and wire my amp up and it works,thanks to you all for your help,advice and instructions, there is a slight hum but I have got my vol on the frontend up high so I'm hoping a few tweaks will sort it,thanks again to you all

[michelevit]

I can confirm that powering an amp on the same computer powersupply will cause unwanted noise.
Solution...
My cab has two ATX powersupplies, one for the mobo and one for the amplifier.

Why don't you just add a filtering capacitor?  That's what they're for and they work very well to combat hum.

I have a surplus of pc power supplies and it was a simple quick and free solution.

[Binkles]

I've got this amp as well, on the left of the picture, where do you get that ground?

Understand that the right hand side is the 12v and ground...

[BobA]

Ground is black and 12V is yellow.  Both blacks on the 4 pin molex are the same ground.