Specs to look for when matching tube pre to SS amp

I would find out what the output impedance of your preamp is, how much capacitance the output stage has and what the manufacturer's recommended minimum amplifier input impedance is. Sometimes solid state amps have input impedances as low as 10 kOhms, which cause problems with tube preamps. I had this problem with my ARC Ref 2 and Gryphon amps.

I believe one "rule of thumb" is the input impedance of the amp should be at least 10x the output impedance of the preamp. My McCormack DNA 500 is one of those SS amps with input impedance of only 10K ohms, and it works fine with the SF Line series preamps, which have relatively low output impedance in the range of about 100 to 300 ohms balanced. I have heard the UltraVerve is a great preamp. Good luck matching.

Input sensitivity is the input voltage required by the amp to output maximum voltage so it is related to the amp's gain. So, your preamp puts out 8V max - this means that the input sensitivity of your amp needs to be less than 8. You will of course find that basically all amps will be below 8 which means that the designers of your preamp aren't dupes. They made it so that it will work with any amp so you wouldn't have to ever worry about input sensitivity....

The output impedance of your preamp is the only spec you really need but you apparently don't have that number. I would ask deHavilland and see if they will tell you. In most cases, since the designers aren't dupes, you don't have to worry about this number either but with tube preamps, you should ask.

The rule of thumb of the amp's input impedance divided by the preamp's output impedance being 10 OR MORE is pretty good to assure that your bass doesn't get lopped off.

The cases where there are some technical mismatches are in fact quite rare (unless the designers are dupes). What happens far more frequently, IMO, is that the sound qualities don't match your desires. In this case, no numbers will help you, only luck and patience will. Good luck! Arthur

The output impedance of the DeHavilland UltraVerve is 600 ohms. They recommend amps that have a minimum of a 10kohm input impedance.

I am currently deciding between keeping a Plinius SA-102 (47kohm input impedance) or a McCormack DNA-500 (10kohm input impedance). I own both, and both are excellent matches with the UltraVerve. It's going to come down to my preferences, but these are two of the best SS amps that I have personally owned.

Well I remember when I bought a Goldman Memesis3 they told me not to use it with a CAT pre; because of the dc-off-set---whatever the hell that refers to. Anybody comprende dc-off-set??

Why do you think you need 200+ watts for small monitors?!
Even at the rated 85dB, this power level would reproduce dynamic peaks over 100 dB SPL in a normal listening position 10 feet away from the speakers.
I know some people claim you need 120 dB capability if you want to reproduce the sound in the middle of a brass band.
Better find good ear plugs if you do... :-)

Thank you! All of your responses have really helped. Serus, I don't know if I can answer your question, but my previous speakers were Dynaudio 1.3SEs (monitors), that I was driving with a Proceed BPA 125wpc amp. @ 5 months ago I bought a Proceed HPA2 which was 250wpc. The Dyns were 86db sensitivity and they had a much improved sound with the bigger amp- not only did everything seem to just 'open up' but highs and midrange sounded more refined. I don't know if that was a function of the increase in wattage or more current. My guess is a bit of both). I therefore have 'assumed' that an amp in the 200-250wpc range would be more compatible with the Focus Audio that are 1db lower. If this thinking is flawed plse let me know :) ..I also thought the Dyns sounded better at low volumes with the bigger amp. I sold the 125wpc amp before I bought the FA speakers, but they too sound nice at low volume levels with the larger amp.

The matching between amp and speaker is more important than the power ratings, as you noticed. It's just possible that the bigger Proceed was a more refined implementation overall. In a small room, I'd look for a range of amps at whatever price level you consider. You might find that some 50W amp gives you the "right combination".
Here is a real story in that regard, where a 40W amp drove 83dB panels to deeper bass than a 150W amp. The latter was deemed by the owner as barely sufficient for the task...
The main reason I asked about the 200W amp is that it seemed odd to play tiny speakers at such high power levels, but I understand your point now.
The motivation to go down in power is simple: watts are not cheap, like many speaker designers would like you to think... To get more power, the amp designer has to make tougher compromises. Sonic ones, like the obvious need for parallel output devices in sand amps and parallel or large tubes in glassware, none of which can maintain the coherency of a single small amplifying device. Just the physics of the circuit tells you it's impossible to compensate for all mismatched characteristics between many different devices.
At the lower price brackets, perhaps the economy dictates the circuit even... IMO the best sonic bang-for-the-buck comes from the moderate power amp that matches your speakers and not from the high power one - even if it matches too.
This concept makes life a bit more complex, but when you're done with your system component selection you will most likely have the best sound for the budget when going with the "optimal" moderate power amp.