What a classy amp, made in Sweden by EBS and a few years old now. It was suffering from an annoying hum, even with no instrument plugged in, I traced this to poor earthing on the preamp panel which relies on a good contact between the chassis and the metal bodies of the potentiometers, I removed the panel and gave the chassis a good rub with some sandpaper where the potentiometers make contact. While the panel was out I replaced the valve which is not a preamp valve, but rather a buffer between the preamp and the power stage. Once bolted back together there was no hum at all, so good to gig for many more years.
