^^
Amazing info. Thanks for making a lot of things clearer.
Yes, Thad summed it up quite nicely.
I had the exact same question a few months ago when I bought my power amp and didn't have a pre-amp. It turns out that my power amp ran quite happily when connected directly to the source (Squeezebox Classic). Since I only had one source, I didn't really need a pre-amp. The SB Classic also has a digital volume control that I was able to use to control the volume.
It turns out that I was losing quite a bit of audio quality with this setup however. Digital volume control apparently drops bits (again, rightly pointed out by Thad and other forum members) - i.e. the sound quality degrades significantly as you keep decreasing the volume. Since my power amp was quite powerful, I was running it at near minimum volume so I was losing quite a bit of audio quality due to my setup! In fact, it turns out that the right setup is always max out the volume at the source and control the volume only from the discrete pre-amp or the integrated amp.
I then decided to go for a pre-amp. I had two options - passive or active. The way I understand it is a passive preamp controls volume by decreasing the amplitude or power of the input source signal, and an active preamp has a separate mini amplifier that controls volume by amplifying the source input signal. The other way to think about it is that a passive preamp is like applying brakes to a car to control speed, and an active preamp is like using the accelerator to control speed.
Many of the discerning audiophiles prefer a passive preamp as it does the minimum amount of manipulation or interference to the source audio signal. As you can imagine, the amplification that an active preamp provides will inevitably modify the sound in doing so. In fact, square_wave once posted about a preamp being sold on DIY Audio that uses a light dependant resistor to control volume - i.e. this type of a preamp even prevents the volume control mechanism (pot) from introducing additional noise. That's as pure as it gets.
On the flip side, many people prefer the way the pre-amp colors or modifies the sound. I guess that's why a tube (or Class A) pre-amp is preferred by many along with a solid state power amp - the tube provides warmth to the sound, and the solid state power amp provides decent power levels. In the Pune HFV meet, from what I read, the Nelson Pass preamp got extremely good reviews.
Anyway, long story short, I just wanted to share my personal experiences with you regarding preamps. In my case, I chose an active preamp as I didn't want to lose signal quality. Adding an Emotiva preamp was a night and day difference - it hugely increased the audio quality, and in many Floyd songs, I could hear levels of detail I didn't even know existed! It is a highly detailed and resolving preamp, especially for its price. It is also built really well.
