SMSL 98E killed my setup?


So today I got the SMSL SA-98E amp from amazon after waiting for 50 days. I was pretty excited since I could finally test out my new passive speakers. My setup up to then was a scarlet solo and a jds atom amp to drive my HD600s. So I unplugged my headphones, connected the rca outputs from the atom into the rca inputs of the smsl, and hooked the speakers to the smsl. When I tried to play music, the speakers made a high pitched buzzing sound not too different from a sine wave, and there was no hearable trace of the music I was trying to play. I started troubleshooting, rechecking the speaker cables were connected properly etc. I noticed that the buzz became much quieter when I unplugged the rca inputs of the smsl, and upon reconnecting said inputs, the speakers made a very loud sound like when you touch a live guitar cable; I immediately turned the smsl off, but the atom amp and the scarlet solo didn't survive the ordeal. Their lights were off and they showed no sings of life. Since then, my atom amp has turned back on but it outputs an
obnoxious sound like the one that came out of my speakers, even without any input at all, and my scarlet solo hasn't turned back on.
Have I killed my scarlet solo and atom amp? If so, was it something I did wrong with the wiring or can plugging a defective amp kill other components through rca?
Any help appreciated

santiagol
Question: When you plugged or unplugged the cables connecting the Atom to the SMSL, did you have the components turned off? If not that is what might have caused the damage.
 The atom was turned on, and I think the smsl was also turned on. I also had the volume cranked pretty high on the atom, with GAIN turned on.
I'm still surprised that the atom and the scarlet died but the smsl is intact
@almarg 
Plugging and unplugging live components into each other can cause damaging transients! Don't do it! Turn everything off before plugging/unplugging cables!
@roberjerman 
I now think that I simply had the volume too high on the atom. I will definitely be more cautious next time!
I will also turn the components off before pluggin/unplugging!
What is a "Scarlet Solo"? A headphone amp? Does it have a volume control and a pair of RCA output jacks? If so, yes you can plug it into the SMSL.