I have moderate gain on the external preamp. I put like -6dB or on the return block to get the volume even with the other (factory) presets. The issue I think is the modeled preamp just sucks all the volume out of the signal chain. For now I'm using an amp block instead of the preamp block and it works the way I want it to. The Quilter 101 has a solid state (class D) power amp so I probably want to use an amp block anyways. I do have a Vox AC30 that I will want to use occasionally though so I might want just the modeled preamp for that.
To simplify, using a blank preset, if I do:
Guitar in -> preamp block -> 1/4" left out -> Quilter effects return
I get no volume. If I do:
Guitar in -> amp block -> 1/4" left out -> Quilter effects return
I get the expected volume level.
Is the the expected behaviour of the preamp block?