But I still have this pan effect (due to delay time changing). It clearly miss a room reverb, but I’m looking for what is before the reverb, do you have a clue ?
You are searching for a sound from the first 15 seconds?
Try a short digital doubling stereo delay with about 4 repeats. Maybe 1/32th , so try 40, 60, 80 milliseconds. These delays aren’t panned hard left and right. The overall sound has little space.
I don’t hear panning, just the exact (digital) repeats that drive the breaking tube amp sound.
I think that’s it, no reverb, just a delay pretending early room reflections.
This is just my idea, maybe something’s missing, though.