Effects loop question with a Peavey Ultra Plus

[Drache713]

So my head has a serial effects loop, no level or mix controls. Just the send and return jacks, no switch to turn the effects loop on or off. I'm running my GNX3000 in the effects loop for basic effects and such (chorus, delay, etc) and I'm probably going to experiment using it as a supplemental EQ and a level boost for solo's. My question is, what kind of level is my effects loop send jack on my Ultra Plus sending to the GNX3000? Is it Line Level or Instrument Level? Should I be plugging the send jack of the effects loop into the guitar input on the GNX3000, or the line input?

 

[WarriorOfMetal]

according to the manual for the Ultra Plus (i still have it on my computer, from when i owned one of these heads), it has a "low-level effects loop" and on the spec page, it says -10dB, 300mV for the send and return.

i believe that's considered "instrument level"