#1
i have a tube combo amp that has an effx loop and external cab
output but this is all .

are there anyway to line in just using the amp without the
speaker so i can use speaker impulse ?
#2
Depending on the amp, you might be able to use the FX Send to your recording interfact with the master volume at 0.
That'll give you the pre-amp, which should be enough really.
If that wont work, you will probably need a loadbox that has a direct out or something else along those lines that can take the speaker load.
There are other workarounds as well, like having a pedal that splits your signal in the FX loop - one end going to the recording interface, and the other end going to a pedal that can mute the signal, such as a volume pedal for instance... just make sure to bring the master volume to a reasonable level before using the amp like normal again after that though
Things with strings:
Ibanez J.Custom, Prestiges, RG8, SR5 bass etc
LP's, Strat, Tele
Noiseboxes:
ENGL Retro Tube 50
5150 III 50W
Orange Terror Bass
#3
i thought about the effx send but that's only preamp tubes
on my amp also i thought i read that no signal to the speaker
could damage the amp
#4
Yeah that'd be minus the power section. Worth trying though just to see if you like it with just the pre.
As long as you have your speaker hooked up to the amp (or well in this case you're running a combo) you're fine. It is essentially the same as killing the signal via a volume pedal in the fx loop, so don't worry about that.
Things with strings:
Ibanez J.Custom, Prestiges, RG8, SR5 bass etc
LP's, Strat, Tele
Noiseboxes:
ENGL Retro Tube 50
5150 III 50W
Orange Terror Bass