"Luckily, Foster, who has worked with the likes of Joe Perry, Melissa Etheridge and Cheap Trick, has an on-site guitar amp tech, Simon Murton to work with, and before each show, Murton will bias each amp while Foster plays Young’s guitar through them. The only certainty is that over time there are going to be casualties mid-show and the other amps will have to pick up the slack.
“We push those amps way beyond where they should ever be pushed,” explained Foster. “We know damn well we're going to blow a few up now and then, but it doesn't matter. I have to be able to sustain a note at certain spots on that stage and it takes all 12 of those amps to make that happen.”
"Foster, however, says the secret is more straightforward, and there is no single overdrive pedal that will do the job. “The thing with AC/DC, in general, their tone is really clean and clear, the tone comes from sheer volume,” said Foster. “To get Angus' tone, and you turn it up all the way until the speaker completely exerts itself, meaning the cone moves forward but can't move back, then you back it off to where it's got movement again. That's where that sound comes from.”
Thereafter you are instructed to hit those strings as hard as you can and make the amp fight back"