I'm having kind of a recurring, transient problem with my GK 400RB-iii combo. Within a few minutes of startup it suddenly sounds strangled. Real quiet and flabby. I've learned that I can instantly remedy this by smacking all my strings and sending a big ugly signal to the amp. It works great after that. Sometimes it does this twice within the first 10 minutes of playing. More often not at all. But most often once. Does anybody have an idea how to permanently fix this? It's an obnoxious problem more than anything else. Turning the amp off doesn't fix it. The only thing that seems to work is a big nasty slap.