integrated amp vs Pre&power amp combination.

The question can't be answered because the answer really depends on the integrated at hand and the pre-power combo at hand, and then of course the peculairities of the physical setup and your application.

If gain is needed there are physical limitations to the integrated and the pre-pwr is the next tier up. However, some pre-pwr are not as good as some integrateds and vice versa. And when you have to sell a product, designers probably get caught up in what's going to sell versus what would've been the best sound for the money in a finished product.

The advantage of the seperates is that preamps are low voltage low current devices and power amps are high current high voltage--too big a power amp in the same box will eminate a strong enough magnetic field to interfere with the preamps circuits, although you can shield like brian said. Also, both pre and pwr in an integrated will often share a common power supply, which is not necessarily bad, but.. if you need a lot of power for your amp its usually best to give the pre its own pwr source too. And, if its a high powered class A amp being horribly inefficient there's going to be so much heatsinking to deal with too it becomes mandatory to stick the preamp in a separate box for cost reasons alone. Tecnically you could have a 5 foot wide chassis and you could get them far enough apart and deal with the heatsinking but its certainly not cost effective, especially from a marketing standpoint. It comes down to matters of cost, performance, and flexibility. If you've got to drive long runs of interconnect to remote locations then a pre is necessary. The only real plus for the integrated is that a passive linestage can be done nicely and save cost and improve performance since there is no cable interface the source would have to drive. Passive control units in place of a seperate pre in a pre pwr combo are not necessarily that great since the source is getting bogged down. Active loudspeakers offer the potential to be the best with the necessary electronic equalization, so from that standpoint, pre-pwr is the best. I don't know enought about those digital loudspeaker systems--the real kind that convert the digital signal into a a soudwave all in one step so...