Swooshing and Crackling

[nickarnal]

Hello. I build an N72 and 2 T15s last August. Every session I hear crackling and swooshing but it is random - there are times when it only happens once or twice and there are other times where it is consistent for five minutes. I imagine that this is a ground issue. Any tips on what to check? Everything is mounted in the chassis and screwed in.

Thanks,
Nick