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

If you didn't change the gain setting on the atom  the impedance mismatch from the smsl might have fried the atom and the scarlet if it was plugged into the atom. 
What you did was plug in rca outputs of the atom (now acting like a preamp) into the inputs of the SMSL SA-98E (this is an integrated amp which means a power amp & preamp in one unit). So, you are feeding one preamp into another (don't do that). It worked fine with the active speakers because the speakers have built in amps and the atom is acting like a preamp in that configuration, which it should.

" What inputs are safe for the smsl amp?" 
Line level inputs, cd player, DAC, tuner, phono amp, etc.

What you needed to use was a power amp only for your setup. That would be rca preamp input, speaker outputs, no volume control or headphone jack.
Unless your integrated can be reconfigured to be used as just a pre or just an amp with the use of jumpers or a bypass switch,it's not possible to plug in an outbourd pre.The inputs are only for source components.
@djones51 I think this is what happened, I certainly didn't unpress the gain button, and looking at the atom manual, it specifies the use of low gain when using it with speakers. 
So from what I understand my setup could work as long as I change the gain button on the atom every time I want to use the speakers? That seems pretty risky if I can fry 200$ worth of equipment at the press of a button or lack of thereof.
@dill : You can connect a preamp into another preamp. Just keep the volume control low so you don't overdrive preamp #2.