Ok, didn't really know where else to post this thread.
Lately I've been keeping myself to my acoustic guitar but I felt for some electric guitar after a while and as I was packing up an old amplifier and just tuning the guitar and started playing. It was all working fine when just playing with the "normal" sound without grain/noise. But as soon as I started the grain, the amplifier made this really high sound like if the volume was on max and it started to beep and I quickly shut it off. I dunno where else to turn atm and I've tried different guitar volume settings and see if that was the problem but it wasn't.
Any advices?