High end stereo preamps? Worth it?

@antigrunge2 

Given high output voltages of modern DACs, the Pre becomes a glorified attenuator.

This was a common viewpoint a few years ago and continues to work well for some, but others who have tried running their systems DAC-direct or through a passive preamp have perceived a loss of dynamics and tonal density and have since gone back to using preamps or buffers.  If you take a look at my post from noon yesterday, you can read about other factors that affect sonic performance with/without a preamp that go beyond simply having adequate voltage to drive the amplifier.  BTW, digital becomes analogue when it comes out of the DAC.

Hey @cakyol , where were you 20 years ago?  If I had known about the $2K limit on preamps back then, I would have saved a lot of money!

@fastfreight 

In each setting, the overall sound and especially soundstage was improved by inserting a preamp.

My experience exactly after trying multiple types of passive volume controls and DAC direct to amp approaches.  I am using a unity-gain buffer, so no gain like a traditional preamp but active buffering of the signal, which seems to preserve the tone and dynamics that I find missing with passives and DAC direct approaches.  To answer the OP, "high end" preamps presumably handle the signal better than lower cost approaches (i.e., better design, better power supply, less shortcuts, better parts) but more dollars don't always equal good sound so to your question of "High end stereo preamps? Worth it?" my answer is, having a preamp or buffer is better than having none, but to the value - it depends on the preamp. 

@fastfreight 

Many have posted how a quality preamp improved their systems. None will be able to tell you the science. To many of us, It just sounds better..

I agree using a preamp (either a unity-gain buffer or an active preamp with gain) sounds better than passive options (and I have owned multiple resistor-based passives, TVC passives, and my current DAC that can directly drive the amplifier using a volume control implemented by adjusting the reference voltage.... out of the signal path).  

Some here have actually shed light on "the science" related to the improvements of active circuitry between the source and amplifier.  The issue is not just a factor of having enough voltage to drive the sensitivity of the amplifier but is also related to driving the interconnect cable, impedance matching, and more. If you search these forums, there are informative posts by knowledgeable folks such as (the late and well-liked) @almarg, and @atmasphere the long-time owner/designer of amplifiers and preamplifiers of the same name.  Nelson Pass has also commented on the subject in his comments about the Pass B1 Buffer Preamp:  
https://www.passdiy.com/project/preamplifiers/b1-buffer-preamp

Wading through the many "passive vs. active" posts here could lead you to some science-based information, but would be time consuming. Below are some comments by @atmasphere on the subject of why active circuitry between the source and amplifier is beneficial:

The reason to use an active line stage is to reduce coloration. The coloration can be caused by the cables and the math that derives therefrom (bandwidth limitations, increased output impedance of the source and thus the impedance driving the amplifier).

Gain may not be needed, but buffering the input and output of the volume control so that the source and amp see a constant impedance is. In this way the setting of the volume control may not also act like a sort of tone control.

The thing is, if you do your design homework, the distortion and bandwidth limits of the active line stage can be much better than those of the source itself and if you do your engineering homework, its possible to insure that the kinds of distortion it does make are of the type to which the ear isn't particularly sensitive.

@georgehifi 
You forgot to post the rest of Pass' thoughts on the subject:

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.

There are reasons many like what they hear through a preamp (or a unity gain buffer) better than through no preamp or through a passive.

@georgehifi 
You have made us all aware of your opinion on the subject of preamps but I thought the readers here might benefit from seeing the whole Nelson Pass quote.
Mr. Pass apparently believes there is sometimes a need for a preamp or buffer, for the reasons he stated in the quote, or simply because some people believe it sounds better with a preamp in their system.
I get that Pass is a businessman but he is also somebody who has never been afraid to march to the beat of his own drum so I do not buy that the only reason he designs and manufactures preamps is for people who want glitz.  I doubt he would manufacture the $17,500 XP-32 three-chassis reference preamp if he didn't believe it added something positive to the sound of his amplifiers in more than 1 percent of systems.
I have no interest in a technical debate as my observations on the subject were already posted on this thread on October 25, at 12:02pm.