This previous post describes the repair of an old Wharfdale SPC 10 active subwoofer. The process did not go as smoothly as I’d have liked, and I consequently thought I’d damaged the unit’s auto-standby feature.

The sub worked when first powered then after 25 minutes it went into standby, regardless of if there was a signal…even a big stinking bass one:

Trawling around the internet for a clue on how auto standby works (and whether I may have broken it) I came across this avgadgets.com post.

Read the instructions!

It turned out my crappy soldering had not screwed the subwoofer. The error was blithely running my receiver’s level calibration with the sub’s volume turned to max. Subsequently the gain on the sub was at -5.0dB so the signal through to the sub is too low: lower than the auto standby threshold in the sub.

The avgadgets.com post tells you what you are supposed to do, which should result in the gain on the sub being around +5.0dB or so at the end of the calibration.