I've always wondered, when discussing passive pre-amps, with and withoput transformers, what is the effect of a passive pre-amp without transformers, which has a varible output impedence from 50K ohms to near 0 ohms at max volume rotation, a point where it should be, for all pratical purposes invisible to amp? How does the sources output interact with the passive pre in relationship to the passives output, or does it? I've never understood any of this. Is it meaningful at all?
Does a passive with transformers present a constant output impedence to the amp? Is it affected by the sources impedence?
Or are these just meaningless questions?