I recall one 'Folk Festival' where there HAD to be Amplification for Main Stage , and the Sound Man was NOT (In the Irish sense) Sound .
Martin Carthy on , Solo , with Vocal Mic and DI'd Guitar ! The 'Sound Man' was working overtime , the result being a completely flat output from the Speakers ! At one point , with Martin doing an Unaccompanied song , there was total silence from the speakers for about fifteen seconds . NOT GOOD !!!