Tube preamp into F/X loop of amp w/tube preamp

[cmhadden]

My amp head has a 2 12AX7 tube preamp. I was wondering if if is possible to run my presonus tube preamp (which has 1 12AX7) in the the F/X loop of the amp or would this damage my amp head? Or would it not be advisible because of sound degradation?

[username1]

Ive done this before with no problems using other brands of amps. It wont hurt anything so it is worth experimenting with to see if thats the sound you prefer.