Did you turn them up to 11? I knew this electronics guy who got his start soldering wires for Apollo rockets and NASA. His name (I think he’s still around) was/is John “Dawk” Stillwell of Freeville NY. He had his own business called Dawk Sound Limited. He specialized in amp mods. Ritchie Blackmore, Keith Emerson, and Chris Squires were among his clientele. Back in the ‘70’s Jim Marshall even came stateside to see what Dawk was doing to his amplifiers. Many of the mods became production items.
Dammit that was my line!
I remember hearing about them... they changed the preamp system and had a few more mods that could be performed. Seems like one of their mods was a built in attenuator to get the overdrive sound at lower levels for small clubs. Man... that was a long time ago!