After working with engineers at Mojotone, guitarist Alex Lifeson is putting his name on an exact replica of the custom amplifier used in his guitar rig. Dubbed the Lerxst Omega, the amplifier was created by Mojotone based on a vintage Marshall amp Lifeson used in the studio while recording the band’s latest album, “Clockwork Angels.” With select modifications made to the circuitry and an overwhelming attention to aesthetic detail, this 25/50 watt amp is a marvel in the world of modern sound amplification. And for a guitarist like Alex, who has one of the most distinctive and recognizable tones in rock music, the Lerxst has to live up to a …