I recently got a used Rivera Chubster and I really like the amp. However, there is a lot of hiss the amp makes when I'm not playing, guitar volume turned down, etc. I've read since it is a higher gain amp, they can be noisy. I've also read somewhere that using a 5751 tube might lessen the hiss. So my questions is, if I get a 5751 tube where do I put it? V1, V2 or get one for both? Thanks for any help.