I don’t know where to put this. My SG keeps on going out of tune between songs. I played one song last night and then went to the next and it sounded flat. I got out my tuner and sure enough it was flat. The only string I have ever had a problem with was the G string but now every string is flat. This is a conundrum. I can’t figure it out. Any ideas?
I've been an SG Special owner since 1967. Gibsons are notorious for the G going out of tune. The reason lies with the headstock design. If you compare the angle from the nut to the tuning machine with your PRS, you'll see that the angle on the Gibson is far greater, and that the PRS offers close to straight string pull.
Why the angle should affect it more or less, I have no idea. But I found the same problem existed with mine.
Back in the day when Gibson designed their headstock, it's possible that players used a wound G - this is just a guess on my part, since 1967 was so long ago my brain from that era has dissolved into dust.
I do know that wound Gs were more prevalent then, I just don't remember what was on my guitar originally.
One of the reasons that PRS designed one of the first Non-Fender style guitars with straight string pull on all the strings was to keep the tuning more stable. The original string pull with the winged tuners that came on the first factory designs was just about perfectly straight. It deviates a little now with the current, non-winged tuners, but not enough to affect the tuning.
However, even the very slight angle from he nut to the current tuner's peg on the G is far, far less than with the Gibson.
Anyway, I believe that's your answer.
I'm guessing that you already stretch your strings well, and that you wind enough wraps on the peg of your Gibson to prevent slippage. If not, do that. Otherwise there isn't much that can be done. You might try a different brand of strings, or go to a higher gauge string. There is something called the String Butler that was designed for Gibsons. It's a non-permanent gizmo that puts the strings straight at the nut, and it just clamps onto the strings. I haven't tried it and can't vouch for it, but I'd sure try if I had to depend on a Gibson for my work.
There are lots of reasons I find PRSes superior to Gibsons, and one of them is staying in tune much better, but there are an awful lot of little tweaks that PRS simply thought through more carefully or in light of acquired knowledge, compared to Gibson. When you get a PRS, you really do get a guitar where the details were sweated over to the nth degree for players.
My Gibson lives with my son in LA. I don't miss it.