Potential Tube Amp Issue

Question

So, I cocked up today. I recently moved house and dragged out my amp head and cab today, hooked everything up and was jamming away to check it all still worked fine. Sounded a little odd, but I put that down to me not hearing for it a while. After about an hour, I then decided to find my delay pedal and stick it in the FX Loop. This is when I noticed I hadn't plugged my cab into the speaker output, but plugged it into the line out instead. I naturally immediately switched the amp off and corrected the mistake, switched it back on and everything sounded perfectly fine. I'm a little worried I may have damaged the amp, as I know you're never supposed to run an amp with no load. What are the chances I've damaged the amp?

Specifics: Amp is a Bugera TriRec

Cab is a Marshall 1960AV

Ran from Line Out to Cab for about 1 hour Immediately changed the cables upon notice of my mistake

Thanks!

Answer 1

If your amp works and if it sounds OK you haven't damaged it. We all know that tube amps shouldn't be operated without a load, but depending on the exact circuit and on the power tubes, most tube amps can survive such a condition for a while, and it looks like yours has survived. I haven't actually experienced a single case where the tube amp would be damaged immediately in such a case. What may have happened is that the life span of your tubes has been decreased a bit by operating them without load.

Some amps switch on an automatic dummy load if the speaker jack is not connected (my Koch Twintone does so); in that case the tube amp doesn't even notice if you don't connect a speaker. You can check if yours has such a built-in dummy load. But if not, no worries, the amp still works and it is probably more resilient than you think.