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

Thanks this is all good to know.

I was aware of the power up/power down sequence but since adding the L509X I leave the power amp on 24/7.

By adding the vintage valve pre, it sounds like I'll be having to power down the solid state integrated instead of leaving it on full time.

I'm only using the valve pre with the 509X at lower volumes, as it really adds to the sound of vocals at lower volumes.

I think wolf garcia's method is best.
I own an Atmasphere preamp and use it with Ayre MX-R amps.
I turn on the preamp first and wait for the DC offset light to go off before I turn on the amps. Luckily, Ayre has a DC sensor that will trigger the amps to enter standby until the problem is corrected.
I think your preamp is emitting DC and triggering the amps to shut down- which is the correct response to DC. Otherwise, they would get toasted.
B

You Never do this ,it creates a surge . Allways do the Opposite 
with tube gear preamp on first until stable ,30-40 seconds then amplifier, shut off in reverse order you can blow your tweeter in your speaker also you hear a pop or thump.  solid state pre not an issue ,or a stand by . But this is a good rule of thumb.

I'm glad this came up. I'm a newbie at this. I have an AR LS-16 (tube) and a SS Proceed HPA2 amp.

The pre-amp has a 45 second warm-up timer before anything will function.

The amp has two buttons. A tiny off/on button and a large large round 'standby' button.

When I turn the system on I turn the LS pre-amp on first then immediately turn on the amp which stays in standby mode until you hit the standby button. The are no audible clicks on pops through the speakers but you can hear clicks in both components.

When I turn the system off, I put the amp in standby then turn it off. Then I turn the LS pre-amp off. This way there are no audible clicks from the speakers.

Does this sound right?

Many tube amp designs shunt the outputs during shut-down.  Some amps will see this as a shorting of the input.