Passive Speaker Output Fried Interface

Hello everyone!

So today I failed to use my brain - the following happened:

I tried to connect my vintage sony Hi-Fi-System to my SSL 2+ interface. Since it only has the red and black connectors for passive speakers as an output, I figured I'd simply make a makeshift cable and connect it to my interface. In the two inputs of my interface I plugged a double mono-jack to cinch cable. At the end of the cinch cable I wrapped around a wire so I could plug it into the output of the Hi-Fi player. It worked for 10 seconds, then a pop came through the speakers as if I had just unplugged them and the interface stopped working. For the most part at least.

What works:

-Power LED is on

-4k Buttons light up

-Gain LEDs work (on startup, shows gain when pushing the 4k button, blinks when dis-/enabling +48V)

-miscellanious buttons (I think)

-USB connection (is recognized by the PC, able to reset and update firmware)

What doesn't work (anymore sadly):

-input (not via mic, not via line)

-output (not via speakers, not via headphones)

What's weird:

-4k buttons glow very bright red when disabled (should be off), when enabled they glow slightly dimmer red

4k button engaged

4k button disengaged

back of the board

Question:

Since part of the electronics seem to still be working I'm hopeful I could try and repair it. However, I lack the knowledge to identify which part might be faulty. Where do I start looking? How do I do it? Is it even doable (maybe too small of a part to replace by hand?)

A few quick inspections don't seem to reveal any obvious faults like undone soldering spots or popped capacitors.