What qualities stand out in really good solid state preamps?

@decooney I have only auditioned the XP-12 in my home and can’t speak to the characteristics of the higher end or older Pass models. 
 

i agree with your observation that people sometimes upgrade only to wish they hadn’t sold or given away a piece of gear. Some folks on this forum post of having repurchased a piece they’d had before. 
 

Many of us get upgraditis. I’ve auditioned gear in my home that I thought sounded better only to find I couldn’t justify the additional cost for the incremental improvement. In one instance a dealer loaned me an excellent Luxman amp. I brought it hone and it sounded great until I put on a large symphonic piece and it couldn’t handle the power requirements of the transients and started audibly clipping! The dealer concluded it was likely because of the 86 dB efficiency of my 4 ohm speakers that drop to 3 ohms at some frequencies. It’s just another reason to audition gear in your home with your other equipment. 
 

@sameyers1 response to socks

Everything on the forum is opinion and based on individual experiences. You can say I’m arrogant. I can say you’d do better to not to get angry and recognize everyone’s right to post their thoughts and find a respectful way to disagree. I hope you can accept my response in the spirit in which it is offered, as a further explanation of how I characterize neutral.

You are much, much too nice.

Neutrality is an acoustics concept BEFORE being used in gear design...

The sound experience is an acoustics experience first and last....

There is too much variations in price levels and needs and synergetical variations to define a rule valuable for all systems,speaking about preamplifications...

People as usual gave their take on the branded named preamplification of choice... Why not ?

But it will be acoustics knowledge ( not only room acoustic) that will matter as much as gear synergy if you have a budget...

What qualities stand out in really good solid state preamps?

in my book for solid state pre’s is that they first and foremost do not damage the music signal going through them

then it would be the ability to adjust and maintain volume level by each input (to allow useful a/b comparisons)

Intially looking for preamp I was thinking features on board dac etc, but then I figured you can't beat a separate preamp and dac from a purist stand point.  I liked the Mcintosh C53 and the Classe' Delta preamp when it came to features.  Then I decided I need simple but high performance and quality, basically inputs and the best volume control of the signal is what I want.  I narrowed it down to a used Pass Labs X-12, Ayre KX-5emp and an Ayre KX-5 Twenty, with the latter being much more even if I could find a used one.  I found one and stretched to purchase the Ayre KX-5 Twenty.  It's solid, the resolution at lower volumes is phenomenal and it's very dynamic and yet flat across the spectrum.  Very detailed and airy, I definetly can tell it's a quality component.  

I didn't do any demo, rolled the dice when I bought it thinking mainly cost is relavent to performance.  With some preamps it's the features, I was just looking for the best I could afford that controls the volume between the source and the amp.  The Ayre KX-5 Twenty delivers that performance I was looking for but there's plenty others that compete.  As we all know, it's how deep you pockets can go in this hobby, the more you spend the more you'll hear in the sound.  I wish I could afford a Ayre KX-R Twenty preamp, but that's the price of putting a decent vehicle in the driveway..