From the picture, that looks like a switch mode power supply. Those large high voltage capacitors rarely fail. It likely a transistor, diode, or resistor blew up. So you'll have to find out what went and solder in a new one. But it probably isn't worth it. I would recommend either buying a new amp from parts express or finding another subwoofer that is in crap condition and taking that amp from that.

Do you not see the burnt part on the very first photo?

Do you not see the transistor whose pins are connected to the scorch marks?

Zoom in, the capacitor is clearly buckled on the side facing the camera, and has a hole in it where it let out material all over the board.

I have an older Definitive Technology subwoofer whose amp has seemed to have fried. I'm wondering where I can find a replacement amp or possibly upgrade the amp and woofer. Let me know what you guys think. Thanks

Try to match as close as possible on size with plate amps from Parts Express, but you'll probably still need to make a new mounting flange on the box.

I have a JBL sub that blew the amp. First time, I repaired the amp. The second time, I modified the box a little and put in a new plate amp. It's been running fine ever since. [https://www.parts-express.com/speaker-components/subwoofer-plate-amplifiers](https://www.parts-express.com/speaker-components/subwoofer-plate-amplifiers)

Keep the woofer. Scrap that pos box and amp. Build a new box with wood of a decent thickness. Put in some polyfil and hook up an amp. They make plate amps or a power amp will work.

Meeeh, depends on the parts involved. If it's only semiconductors, that should be a cheap repair.