Dumb question......why do you need a preamp?

I run a 'vintage' audio system (so, equipment from the 1960s / 1970s; and things like a Reel to Reel tape deck, etc.) and I recently switched from a fully integrated solid state receiver (which is basically a tuner / preamp / amplifier all in one unit) to a tube preamp / dual solid state monoblock amplifiers.

In all fairness, the receiver I had was a very good high output unit for it's time (160 wpc) and the sound quality was also very good... I have noticed, however, what I feel is an improvement in overall SQ with the separates setup; and more specifically, adding tubes in at the preamp stage adds a certain quality and fullness to the sound that I did not even know was 'lacking' in my previous configuration.

I thought perhaps it was simply confirmation bias on my part; but I have gotten similar comments from my family members that they too hear a pleasant difference since my 'upgrade'...

With an integrated amplifier you do not need to use a preamp, but there may be reasons you might want to. If your integrated amplifier does not have a built in Phono section is one reason off the top of my mind to add a preamp.

All the best.

Two reasons to “need” a pre-amp

1) to deliver a particular sound that you like 

2) features that may be useful. A volume control would be most common.  
 

If you already have these then you do not need a preamp.  

Preamps do impedance matching which is very important. I've played the game hooking up DAC's directly to my Power amplifiers but in the end my active preamp always sounded better!

@erik_squires

A good example of having separates is an electrostatic speaker

Can you explain what this means, please?