Thank you Phil for your explanation
Our advice is that the sub should get signal from preamp.
Please, how can the amp "improve" the signal from the preamp or source? I think we know a thing or two about amp design.
The amp amplifies the signal and the noise too. And you want to feed that to your sub?
What's a sub? It is just a low pass filter with amp and speaker.
I had read several articles describing advantages of connecting subs to amps instead of preamps, here's a quote from PS Audio:
"each power amplifier has its own sonic signature. If you use the amp’s output (rather than the preamp's) to feed the sub amp, you maintain sonic consistency and improve system synergy."
As you state, you know a thing or two about amp design, probably a lot more than PS Audio and certainly a lot more than I do, so I will keep my subs connected to my preamp.