SHO hiss when turned on

[geiristudio]

I'm making a SHO, and I've successfully made a few of them with no problems. However, this ones being a bitch. When I turn it on there's a lot of hiss. It sounds like it has a huge amount of gain, but the hiss isn't related to the pot because it stays the same no matter if I turn the pot up or down.

Can anyone give me any ideas what could be causing this ? Like I said, I've made others that sounded fine.

Thanks!