Hi. I'm not an incompetent person; I do motorcycle mechanics on old jap bikes for a hobby, have been screwing around with computers (up to light programming) for 15 years, and have used a soldering iron once or twice. I've used basic wiring diagrams to troubleshoot motorcycle mechanic issues before.
I bought a pair of Dayton B652's new off of Parts Express, an external USB DAC (Creative X-fi SB1240) off of craigslist, and a lepai 2020A+ off of craigslist. The lepai didn't come with a power supply, so after a little research (people saying the 12v 2amp that comes with it is underpowered, should use a 5amp for its full potential--which 5amp? one guy recommended a particular one off of ebay, Li Shin, that did not produce noise on his, after buying another 12v 5amp off Amazon that did produce noise and did not increase volume on his) I got this:
12V 5A AC DC adapter power supply Li Shin LSE9901B1260
power supply on ebay.
All the parts finally came in the mail.
I inserted the wires into the back of the speakers, and then to the amplifier. (It's only a 2.0 system, so yes, I did this part correctly. I've hooked up many speakers and amplifiers over the years, just never a 'home-built' system) I then plugged the power supply into the wall. Then to the amplifier. Flipped the switch on the amplifier. Blue light! Good! :D
I turn the volume all the way down. I plug in the included RCA-to-phone cable's phono side into the Lepai's "mp3" input. I plug the RCA ends to the output of the X-Fi DAC.
Lastly, I hooked the external sound card to the computer--originally, the USB cable I was using to hook it up seemed to be a little less than par (the guy who sold it to me gave me two cables in the box, one that looked 2nd rate with a little bit of insulation torn away, and another nicer one. The nicer one was being used elsewhere, so I grabbed the second rate one, figuring it would at least work if he included it in the box). I think this is not the problem, but I am mentioning it for the sake of being thorough and not leaving any detail out.
The reason I think it was actually less than par is that the blue LED light on top of the sound card was dimly/partially lit, maybe even flickering, but using the nicer wire a minute later produced a full, solid blue light.
Hooked that up. Windows Vista SP2 identified and started installing the drivers. I'm sitting there wondering about the quality of this cable, when all of a sudden, I smell something--christ, what is that smell? I panic, because I have smelt this before at some point, maybe soldering, maybe breaking something else in my childhood, but I know that's a bad smell. I immediately unplug the sound card, wondering about that cable, smelling the sound card--it smells like it on the outside, but it seems fine. I go to grab the better USB cable from the table nearby. I walk back. Smell is stronger. And I notice the amplifier light is out.
I disconnect everything but the power from it. Turn it off, turn it on. Blue light comes on, then quickly dims. I do this two or three times and get the same result. I unplug the power. I walk outside to try and air out the smell. My roommate walks out a minute later and asks if something is burning.
What the hell happened?
I used only a setup thoroughly vetted by many others with a great deal of experience. My only guesses are:
1. The power supply was actually a piece of ****, and not correctly spec'd
2. The amplifier, which I got off of craigslist, was actually dysfunctional
3. Something with the DAC?
I consider #2 to be unlikely, because the guy seemed really honest, and even told me that (I asked him if he was SURE it worked, because I had recently bought an amp for a friend that didn't work off of CL and the guy claimed it 'must have been damaged in transit') "If it doesn't work, come back to me and I'll give you back your money. That guy was full of ****, sorry you had to put up with that." He was a well dressed, nice guy.
#3 is a long shot; I highly doubt an error there would blow the amp. I didn't even send any music through it, and the cable error seemed to be undepowering the unit, not shorting anywhere.
Any ideas? What should I look for?
Here are some pictures from when I took it apart.
The whole board, for context:
Back side of the power input here, looks fine:
The power switch; doesn't look like the best soldering job, but looks fine:
Power knob (with a blue glowing LED around it)... I think it's ok too.
Some of this looks a little suspicious:
Pretty clearly some burned solder joints here:
The top side of those burned solder joints, where it connects into the Tripath chip:
WHY ME? I was so excited. I guess I should be thankful the least expensive part is the part that blew. I only paid $10 for it.