If a bad joint is causing the problem the most reliable technique for reflow is to add just a bit of rosin core solder and only add it if the joint needs a bit more solder. Not sure if this is what you mean. If you are adding only flux to the joint when reflowing - adding more flux alone to a joint often makes things worse because the problem can be a cold joint that already has excess flux in between the wire and the terminal or pad.
It seems that we see people posting about using separate flux a lot lately. I'm guessing there is a YouTube out there suggesting this. It is not a good way to do our kits, point to point, or thru hole soldering in general. Rosin core solder has all the flux needed.
Yeah, maybe I was not clear enough; I have mostly just added some rosin core solder, like you said, though in some cases, I have just added flux depending on the situation. Will take that into account moving forward, though! Most of my experience is from SMD soldering, where I learned that technique. I didn't know it was not transferable to THT.
That kind of noise is almost certainly environmental. Have you tried the Crack in a different location? There may be some device in close proximity to the Crack that is spewing out that noise and it is simply being picked up by the Crack itself. This would be even more likely if the noise is present with nothing plugged into the inputs and the volume pot turned all the way down.
Now that you mention it, the issue actually appeared when I moved to a different city, so you might be onto something here. I have, however, recently moved once again to a different place in the same city, and the noise is present at both places. Maybe it is related to some of my computer equipment? I'll try to bring the Crack to my workplace and check if it's still present there. If this is the issue, are there any places where I might add shielding or filtering to mitigate this in the amp?
Are you using an adapter with the 6sn7? Maybe back to the 12au7 temporarily...John
I have replaced the 12au7 socket with a 6sn7 one completely, so I will unfortunately not be able to do that. I have, however, tried switching out the Ken-Rad tube with a Raytheon one with no effect on the noise.
Once again, thank you so much for the help everyone!
