The Best Preamp is no Preamp?

Bought a Carver TFM amp in the mid 90s. Sounded great with CD player going into it directly. I used the gain knobs on the front panel for each channel as volume knobs. Sounded clean.

Sometime around 2008 I bought a new NAD preamp...entry level stuff @ $700. I was expecting to lose a little resolution going into the Carver. Sounded soooo much better. More body, more bass...it had this softness and smoothness. It did not make sense at the time.

I had to turn the gain knobs on the amp all the way up to max (as recommended by the Carver manual) to use a preamp. I thought it was going to blow up...but it sounded beautiful.

The class A gain stages in preamps are designed to handle very delicate signals much better than the gain stages in your average amp.

Working Audio Engineer here. There are three functional ranges of signal:

• Mic Level - This is the miniscule signal that comes from a microphone. It’s tiny! That’s why microphones are run into preamps. The preamps job is the amplify the signal to:
• Line Level - This is the regular, useable, routable signal bouncing around a mixer, compressor, EQ, ADC, etc etc etc, including your DAC. It’s strong enough to power headphones, but you aren’t really gonna move speakers with it. That’s why you feed your line level signal to a speaker amplifier so you get:
• Speaker Level - This is when you’ve got serious juice and could do some damage if you aren’t careful. Whether it’s 20W, 200W, or 2000W, you’ve gotta make sure you are sending the right level to the right gear or you can blow things up.

So... No, you don’t need a preamp. Your DAC is already outputting a Line Level signal, which is exactly what your speaker amp expects. Why add more gear, more noise, more devices to the signal? Could it help - maybe. Could it hurt - definitely. Sound reinforcement systems don't have pre-speaker-amp "preamps" as a concept even.

(In case anyone is wondering, my at home rig at the moment is a Peachtree Audio Nova125, which has an integrated USB DAC. It's the only unit between the computer and the speakers.)

Sounds better, or different?

Time will tell you which is better for YOU, but usually, with every component in an audio system that has synergy, a pre-amp included provides the most enjoyable music reproduction.

Logic suggests that adding a complex preamp with many active components is likely to degrade sound by the distortion introduced in an otherwise pure signal passing from source to amp/speakers.

So what I'd like to hear on this issue from someone qualified is:

If a particular preamplifier can improve sound compared to eliminating it, what is it that the preamplifier adds or changes that makes the sound better?

And what is it that was wrong with the signal from source that required improvement?

Absent an (active) preamp one is effectively listening to the source device's output stage, which is most cases has been designed to drive a preamp and not a power amp. In addition, many digital volume controls lose resolution at lower signal levels. In your specific case, it's relevant that the Chord equipment has both a very well designed output stage and a very high quality digital volume control implementation. I'm not surprised that the setup sounds better than with the Marantz in circuit. Not only are you eliminating the electronics, but a set of interconnects. To echo previous posts, given well designed source electronics, no preamp will most likely be better than a poor one. Lastly, preamps  generaly do, of course, provide source switching which many people need - statement of the obvious perhaps, but relevant nonetheless.