I recently bought the book called 'The Recording Engineers Handbook' by Bobby Owsinski. On Page 56, he says...
"Why A Separate Preamp?
You might ask, if nearly every DAW interface and console has its own mic pres, then why use an outboard one? There's usually only one answer: because a dedicated unit sounds a lot better.
An outboard mic pre generally provides higher highs and lower lows (meaning it has better frequency response), and it's sound output is clearer and cleaner."
A little later on the same page, it says the following...
"Vintage Mic Preamps
They just don't make them like they used to. At least that's what a lot of engineers think when selecting a mic pre. There's a sound to these units that's been difficult to duplicate in modern gear, except in rare exceptions. Because of this philosophy, some of the most desirable mic amps were made in the 60's and are actually cannibalized sections of recording consoles from that era.
So why does the old stuff sound different (let's not use 'better' because it's such a relative term) than the new? Very broadly speaking, it's the iron inside, meaning the transformers and inductors used routinely in older gear that gets substituted with modern electronic equivalents because of size, weight, and cost. So why not make transformers like they did back then? Although some companies try, the fact of the matter is that many of these transformers were custom made for the particular unit and just aren't available anymore. Another factor in the difference of sound can be attributed to the fact that older units used discrete (individual) electronic components that could be properly matched to the circuit, while modern units tend to utilize cookie cutter-type integrated circuits (a complete circuit on a chip) to attempt to achieve the same end."
Thought this was an interesting take from a pro and kinda validates my own affection for vintage gear. Curious about other's on ts.com thoughts on this subject.
[***Note that the above passages were taken directly from 'The Recording Engineers Handbook' without permission. All rights are reserved by Bobby Owsinski.]