Is it safe to plug directly into a power amp?!

I read a statement in a recent post that I cannot locate using the search feature. Someone out there stated something to the effect that "if you have a good bass, who needs a preamp, just plug directly into your power amp." Is it akin to using a preamp with flat settings? Is it advisable? Consequences? Anyone actually done this and lived to tell about it? I'm really curious now, but I'm not going to try this with my Q5 until someone can attest to this.

 

Thank You!!!