Oscillating pedals while amp is in standby...

[oregomike]

So, I ran across a weird thing today. I was doing my usual practicing. Had some pedals going; Afterneath, Belle Epoch Deluxe, etc.
After a while, I took a break and switched to standby. Came back after about an hour, and switched the amp on and was greeted with this super loud hum and had to immediately turn the amp off. It sounded like everything was turned to 11 and left a pedal cable unplugged somewhere. Seriously freaked me out for a sec. Checked volume (maybe I accidentally hit the volume knob or something). Checked cables. Nope. Everything was the way I had left it. Then turned off all of the pedals and tried again. Hum was gone. Everything back to normal. I turned the pedals back on and everything was fine.

So, question: Can modulation pedals, specifically reverb and delay that have some oscillation, cause this? Should I be turning the pedals off while amp is in standby? This really was a horrible sound I've never heard from my amp before. It sounded like the tubes were going to explode. I'm sort of a noob with tube amps, so maybe this is a thing I need to be aware of.

 

[Grandy]

I have a cheap analog Artec delay. At one time I was playing with the knobs, turned the repeats up for self oscillation, then turned it off. Later I turned it back on and it was oscillating loud as you know what. I'd forgot the repeats were up. The pedals you mention are digital but oscillate so ... I have the Afterneath and you have to be careful with the knobs not have it out of control.

 

[2L man]

I can't think any direct mechanism between turned On effects and then turning Stbt switch On after a break. Switching Stby On just make amp operate and amplify the sound what effects and guitar possibly produce. If setup is sensitive to this it could happen anytime? Then try guitar volume first and effects volumes which are On towards the amp and finally amp volumes and noise source is before the volume knob which kills the noise.