[HzMeister]

As the title says, I'm wondering if anyone can suggest a good amp to run from inside a computer that fits the following criteria:

Can be powered off of the 12v molex rail so when the computer powers up/down, the amp does too.
No on/off pop!
No interference, static, humming, noise
Sufficient enough to power two small bookshelf speakers from low to moderate volumes
Accepts a 3.5mm input or rca
Under $20

Any ideas?

[Speedskater]

I would look for a small power amp with it's own power supply.  Then use a power relay controlled by the PC's 12V supply to turn it on/off.

[HzMeister]

Any reason not to run directly off the 12v rail? It's a good quality seasonic psu with less than 1/3 of it's available wattage being used at max load and an overabundance of amperage.

After looking some more into this, others have mentioned that running a class t(d) amp (ta2020, tpa3116, etc.) will cause too much interference due to the fast switching nature of the amp. Given this, the tda7297 seems promising since it's a class a/b amp - not to mention that it's ridiculously cheap. The only thing I would be concerned about is that it only has a single 2200uf cap from the power supply. Will the single stock cap, or even an upgraded cap, be sufficient enough to smooth out the relatively dirty power? If not, is there any way to add more/bigger caps, etc. to clean it up?

[hifters1]

Not under $20 but:  http://www.cart100.com/Product/16959277398/

[randytsuch]

A PC is an electrically noisy environment, and the +12V from the PC supply will contain noise from the PC.  Just because your PC power supply has enough power on the +12 for an amp doesn't make it a good idea.

This is not an optimal solution, but it depends how much sound quality matters. 

IMHO, if sound matters, I would look for another solution.

[Vapor Audio]

Watts is a very simple equation = Amps x Volts.  Cars can make a lot of watts at 12v because they have a boat-load of amps, you won't have that off a standard wall outlet.  Best bet is use a separate standard 120v power supply inside if you want any sort of real power output. 

[krikor]

How about this? Not sure it has enough power for your tastes, but:

http://www.parts-express.com/dayton-audio-dta-2-class-t-digital-audio-amplifier-module--300-385

For that matter, there's a bunch of other possibilities at parts express:

http://www.parts-express.com/cat/audio-amplifier-boards-modules/3464

[HzMeister]

I ended up trying the $5 tda7297 for kicks and... it works really well. Hooked it up to the 12v rail and it powers on like a champ. There is not interference when using an external source such as an mp3 player but I'm pretty sure a create a ground loop when using the onboard sound card because I get massive feedback. A cheap ground loop isolator should fix it - I'll report back.

Once I finish doing the salis upgrades this little amp should be awesome.

edit: forgot to mention. dropped those garbage micca speakers for some pioneer bs22. night and day difference.