So many users of the line 6 spider iv amps have had issues with the tones going thin or tinny, or muffled and low volume etc. I have a line 6 spider iv 120 and had the same thing start with mine. Well mine was what I call a cascading issue that led me to find what this issue is probably in almost all of your problems too. Seems the main board or brain has a few components used in circuit boards called voltage regulators. basically is drops the voltage down to what it needs to be and then the extra basically causes heat or is the by product which is correct and normal. the regulators have little metal tabs connected as a heat radiator to get rid of heat.......well the one regulator , which is one right beside the plug from the amp supply is the one that gets a little to hot and has a built in kind of thermal safety and kicks out or doesnt run like it should and that is when the sounds get weird, cut out, reset amp, etc. mine caused one of the solder joints on its 3 connections that was weak to start to crack and then when it got warmer it really kicked in to awful mode. so the solution? it is simple and cheap like 47 cents..... they make a heat radiator or fin that attaches to it with a clip, screw, or a thermal glue that is nothing more than an aluminum piece with fingers that is about size of my thumb and now not one issue ever!!!! you can get them on ebay, amazon, etc. there are 2 voltage regulators that are side by side on board and have metal tab, 3 legs connected to board. easy to just attach them and heat issue is gone!! hope this helps someone.