all tube phono preamp creating a crackling, fire-like sound


Hello
I just purchased an all tube phono preamp from an Audiogon seller. the preamp uses the following tubes:
5u4gb, Ob2, 6v6, and 5 12ax7. My problem is that one channel sounds totally awesome but the other channel is unlistenable with a crackling, fire like sound which a friend of mine said sounds like frying bacon. I have changed all of the tubes except for the 0b2. I have also tried a multitude of various interconnect cables, none of this has made any difference. The sound will go away for a couple of seconds and then it comes back, it also comes in waves, starting off low and then getting louder. I also ruled out it being a speaker problem by switching  speakers and their channel. 
Does anybody out there have any experience with an issue like this, and if so, what was the problem and how did you resolve it? I love this unit and I'm about to send it back the manufacturer, where hopefully the problem will be resolved.
thank you
dpoud
That sizzling sound is something Ive heard many times I was using a Schitt Freya and had to replace tubes often I was paying extra for the higher rated hand picked tubes and still the sound would return .Ill say one thing you get what you pay for .I recently got fed up and spent some cash for a Mcintosh c2600  Absolutely night and day My system is a Mcintosh 452 into a C2600 wilson sophia 3 speakers audioquest water xlr and a Mcintosh sacd player I have also just purchased a Pro-ject rpm 5 carbon turntable .Im in NYC so we are under a super quarantine right now .I have no regrets on my setup and now have plenty of time to sit and listen.Spend as much as you can afford to on components.Your ears will thank you .I often purchase used on this site.
I had the same problem that you reference in your post.  I went through a process of elimination that felt like eternity.  It turned out that there was a bad tube.  Double check your tubes....  Good luck!
That is exactly what a tube sounds like as it begins to crap out.  It can last a long time like that but eventually it will wear out and quit.