Deafening noise once amp is turned on

[sonam]

This amp just went crazy on me; it gives out an annoying, screeching, loud, siren-alike noise when I turn it on, deafening really deafening. What could be the possible cause to that? It's a 2speakers hybrid amp btw.

 

[gsonique]

This amp

What amp ?
looks like you have oscillation.

"In plain English, the transistors have a frequency where their gain rolls off. This is the limit of their frequency response and it causes a phase shift that gets fed back through the feedback network (that sets the gain of the amplifier and reduces distortion.) Here's the important point; IF the gain of the amplifier isn't properly rolled off to unity gain at a point below the frequency cutoff of the transistors, then you can get oscillations. This is more often a problem with more modern amps that were designed for very wide band and high slew rate. "

 

[sonam]

A Marshall VS230R, I turn down all knobs and the problem still persist.

 

[gsonique]

Try pluging in and out your 14"jack in all the available 1/4" ports with the amp turned off.

 

[sonam]

that method works! everything is back to normal, thank ya!