High pitched squeal when the input jack is used
It doesn't matter whether all the controls are set to zero. Or, whether a guitar is actually plugged in. Once the 1/4 inch jack makes contact with the input and the amp is turned on it squeals loudly. I managed to fix it somehow and the amp worked. Then I began to change the channel presets and when I turned the amp modeling knob to insane it started happening again. Then I remembered that's exaclty what I was doing when it triggered the first time. It sounds like the amp is in some sort of infinite feedback loop. Absolutely nothing I've tried will remedy the situation. It's a Spider II 75 Watt Amp.
Music - Line 6 - Spider Iii 15 Modeling Guitar Amplifier 15 Watt
Answers & Comments
Sounds like your master volume is turned up too much. The channel volume will make the squealing go away(caused by high gain and humbuckers). The best thing to do is dial in your favorite presets and change the channel volume to the correct level with the master volume where you usually keep it. I use my Spider Valve at master volume at about noon and the channel volume between nine o'clock and noon. Let me know if this does not solve the problem......