This ^^^
From posts on this thread I've been getting concerned that I've had levels /outs / DI boxes completely wrong for 40 years. However, aside from me giving specific voltages for the 3 levels (agedhorse has rightly used more generalised values but not miles away from my guesstimates), I was saying the right thing. I tried to say from the outset that sticking a standard DI box between the combos speaker out and the speaker seemed like a bad idea. I was unaware that the range of DIs available would allow this, so I've learned something... I think. LOL