Turning off tube preamp first sends solid state amp into protection?


I have been experimenting with using a vintage Luxman CL40 valve preamp as a separate preamp stage for my L-509X integrated. Because I leave the solid state amp on 24/7, I accidentally turned off the preamp while the 509X was still in Separate mode. The integrated immediately went into protection mode with the power light blinking. I powered it down into standby mode, then brought it back up and it remained in protection mode. It wasn't until I unplugged the 509X and plugged it back in that everything was cool. 

Did I do any potential damage here? What it it happens again? It's pretty easy to accidentally turn off the preamp when I'm leaving the 509X on all the time.
128x128jsqt
 I definitely agree with what some of the other folks have said here about operational sequence.  I always try to remember this about my main amplifier: “last on, first off. “
 
 I switch on everything else first and wait until it is fully powered on and only then turn on my main amplifier. When I’m done listening I switch the main amplifier off first before I switch off the other gear. 

 I hope this helps. 
The turn on/off order has nothing to do with tube vs. solid state. You turn on the pre-amp and sources before the power amp because the amp can’t send any of their on/off noise to the speakers until it is on. And you turn off the amp first for the same reason.
Thanks guys. Small correction to my post: When pushing the standby button on the amp to the standby position there is a tiny pop from the speakers and a click within the amp. Turning the pre-amp off first (I don't do it anymore) makes a loud pop in the speakers.
It’s pretty easy to accidentally turn off the preamp when I’m leaving the 509X on all the time.
My suggestion is use a IR remote controlled plug/outlet for the CL40 valve preamp and a remote control with macro, program a set of command sequence to turn off the CL40 valve preamp:
Mute the L-509X, change the input out of HT bypass, power OFF the remote controlled plug/outlet for the CL40 valve preamp.
To turn on the CL40 valve preamp:
Mute the L-509X, change the input out of HT bypass, power ON the remote controlled plug/outlet for the CL40 valve preamp, change the input to HT bypass, un-mute.
smh @ wolf_garcia. Do not listen to his awful advice.

ALWAYS power the amp on last!
ALWAYS power the amp off first!