Desperate for some amplifier help!!

[vast]

I grabbed an ebay 12v bike amp for my build but it seems as though there isn't a ground that I can hook up, so I'm getting a lot of hdd noise through the speakers. 
Looking at the reviews http://www.dealextreme.com/p/100w-hi-fi-stereo-amplifier-for-car-motorcycle-color-assorted-34408#forum it seems that the pcb isnt connected to the case for ground 

I've seen a lot of people having mixed success with these kinds of amps, so I'm thinking of just grabbing some usb speakers tomorrow and hacking the amp from inside.  Is this a better idea to go for?  Or should i take a chance on another 12v bike amp?

I'm hoping to have a massive push this week so that i'm in a position to get my steel CP fabricated the week after.

Thanks in advance fellas!

[BobA]

Check the jack for mp3 input.  It should be attached to the metal case and therefore any of the screws on the back should be case ground.  You could also check the RCA plugs for audio in.  The outside of the female fitting should also be ground.

I have a different model and it was easier to remove the 12V from the PC and use a wall wart of the appropriate power.  Got rid of the noise completely.

[vast]

Cheers Bob, the rear and front panels are separate from the main chassis.  I did try screwing the ground into the rear of the amp with no joy.  I basically have the adaptor from the amp connected to the 12v (red) and common (black) on the molex with an extra cable attached for ground from the 2nd common on the molex to a screw on the amp, sound right?

When you say remove the 12v from the pc are you talking about just using a standard wall outlet power supply?

[BobA]

Yes I use a stand alone 12V plug in the wall (wall wart) and use it to power my amp.

[whammoed]

Typically red is the +5v and yellow is the +12v.
An amp has to have special design considerations if using the PC's power supply or it will be noisy, so definitely use a separate supply.
I have built a nice little chip amp that can run with no noise from the pc power supply, but don't know if i'll end up producing it for my website.

[elkameleon]

http://forum.arcadecontrols.com/index.php?topic=111337.msg1187553#msg1187553

I had the same issue, had to use a wall wart to fix the issue, it was cheap and easy (I had a junk 12v supply ready for the taking).