The load was 3 ohms. It sounded great, until it didn't sound at all. It was almost inevitable. I can see what they've done and why they've done it. I have another version of the board (also driving a 3 ohm sub) the specifications show 12-24v (50w+50w+ 100w) - but it does have a small heat-sink. On the blue-tooth version they decided it could cope with max 20v without the heatsink if they reduced the claimed output to 25w+25w+50w. Why wouldn't they - it saves money.That must have been playing fairly loud? What speaker impedance was used? And how did it sound before the failure? Is there any visible sign of failure?
So others can learn from this experience without repeating it.
Despite the general anti-Chinese sentiment going around, I have great respect for them. They don't mess about. I told them it blew-up, they said, "Your money will be refunded within 3 days."