What qualities stand out in really good solid state preamps?

Recently I posted on the Herron HL-1, asking people what they thought, how it compared, etc. It's been sold and that's ok. The search continues. 

But it raises a question I'd like to ask folks:

What attributes do you look for in a good solid state preamp?

Some qualities — quietness, durability, seem pretty obvious.

But what other criteria do you use to differentiate between solid state preamps?

How can they differ and what matters to you?

Please let me know!

P.S. As I've looked around, I've begun to learn more about some of the legendary preamps — made by companies such as Threshold, Ayre, Bryston, Pass, Apt-Holman, and others. It's good to have these names as references, but it would be even more useful if I knew what these brands conveyed, sonically. I've played with the idea of getting a newer Schiit preamp and then I wonder -- what if there's a "classic" preamp out there, used? What would it deliver that was worth searching for?


They are typically very quiet. Neutrality but not at the expense of texture and proper color. Most S.S. preamps I have heard dont get as many things right as the more neutral/linear leaning tubed models. Perhaps oversimplification would be a good word to apply to many S.S. preamps.

I think it more advisable to feed your S.S. amp with a tubed preamp and in my experience this seems more common. Very few if any disadvantages to tubed small signal devices versus tube amps which need to be matched more closely with speakers. Especially true of my OTLs. 

Had Pass XP-12 into Rogue ST100 tube amp. No problems and sounded good. 
Matching tube preamps (typically higher output impedance than SS counterparts) to solid state amps (typically lower input impedance than the tube amps) is where you need to be careful. Everything else is a matter of sonic preference. 


I think it more advisable to feed your S.S. amp with a tubed preamp and in my experience this seems more common.

It's more advisable if the question is "What's better? Tubed or SS preamp?" But, if you read the OP, you'll see that is not the question. It's not an "either/or" question. It's about the differences between SS preamps. 

I find it very amusing to read that apparently, for some, there isn't audible differences between solid state preamps?!? 

Come on.

Every circuit has a "sound", even when it seems very transparent / neutral, if you compare it with another circuit, you will spot differences. It can be "more drive", "more depth", stronger bass, whatever. Solid state preamps DO sound different, just like the rest.