Bass amp vibration

[Nigbassman]

Hi, I've got a Hartke a100 combo bass amp. works fine for about an hour or so but then when I play G on the E string, I get a terrible vibrating warble (can only describe it as a fast 'wow wow wow'), all other strings and notes fine. Any suggestions what i can do about it? Thanks

[BassmanPaul]

Could well be a flaky decoupling cap. A tech should be able to fix it for you.

[Nigbassman]

Thanks Paul, i appreciate it!