Audio Research SP-11 MK2 ...

Is it still consider a top class preamp or it is already outdated ? Is its phono section still excellent when comparing to other top class phono stage ?

For classic equipment it is good.
Compared to the new stuff at way more money? No it is not.
"Top class" no. it is no longer 'top class'
It was made in 1985!! that is a pretty long time ago.

I own an Audio Research Sp-15, the model after the Sp-11 which still is a two chassis affair. (and it uses the same phono section of the Sp-11)
I keep it around to use it's phono section..
But as a preamp it is not as good as my new Bryston BP-26.

I also had an Audio Research Sp-10, and i am sorry but the Sp-15 killed the Sp-10 in nearly any way i could think of. And i gladly sold the Sp-10 for twice what i thought it was worth, but still $800 less than the average asking price!.(and selling the SP10 basically got me the Sp-15 for free) i will not be selling my Sp-15 anytime soon... Even though i hardly use it...
If you are paying $1,500 or so for one, then it is a fair deal.. a lot more money than that and it is an overpriced boat anchor.
Wow! that was really interesting. Before I purchased my REF 3, I retubed my SP-11 MKII with AR supplied tubes and I have to tell you I with several of my friends over about a week compared my borrowed REF 3 (dealer demo) with the retubed SP11 MKII and several other borrowed pre-amps from the dealer, including other AR pre-amps and the re-tubed SP11 MK II held its own quite nicely. We were hard pressed to hear major jaw dropping differences. There were differences and the REF 3 ultimately was a better pre-amp, but blown away? not close. Also, the re-tubed SP11 MK II actually was better than the newer AR pre-amps in our opinion. I tried hard to justify purchasing the REF 3 and made up many excuses, but keeping the SP11 MK II would not have been a mistake. I wanted a remote control pre-amp (getting lazy) and compared the SPII with several remote control units and not one justified the huge increase in cost. Not even the REF 3. I bought it anyway and it is great, but I really didn't need to do it. The gentleman that I sold the SPII to loves it also. I would say, re-tube the pre-amp with proper tubes from AR before getting rid of it. In my opinion, with all respect to Elizabeth, it is still one of the best out there. Re-tubed.

I have had my SP-15 for about 10 years now. I sent it in to ARC in 2004 due to a bad umbilical cord and they refurbished it while it was there by replacing all of the electrolytic caps in the power supply. About a year and a half ago, I bought some NOS tubes for the phono section. The difference in sound blew me away. I am still enjoying my vinyl as if new with these tubes. After my SP-15 has been on for about an hour, I can sit down and enjoy the music, but the music gets more fluid (best way I can describe it) after it has been on for 8+ hours. I have listened to the REF 5 with the REF ARC amps on a different system, so a bit out of context. Very nice sound, but I don't feel like I am missing anything. Good thing, or else I wouldn't be able to sleep until I found a way to aquire the REF 5. As for remote; that's what the kids are for...
I owned an SP-11 mk II for a number of years. In its time it was one of the best preamplifiers available, and it gave me a lot of pleasure. It is still good, but I believe it to be surpassed by the better preamps out there now (I replaced it around 1990 with a Jadis JPL/Vendetta SCP-2B combination, as the tubed JPL was more to my liking and the Vendetta was a quieter and better phono stage than the ARC's). It is not really as liquid or dimensional as a great tube preamplifier, and its solid state circuitry is not as good as more recent mainly solid state preamplifiers I have heard, like the Lamm L2 (the tube in that unit is in the power supply) and Boulder units. It's very good as far as vintage equipment goes, as Elizabeth says, and it does have some very useful features that you don't find in modern units (especially for listening to vinyl, including a mono switch and a knob in the front for some cartridge loading). I have found it interesting that it does not seem as prized in the used market as the SP-10 that it replaced in the ARC line.
I recall the ARC SP-10 having legend status back in the 80s. That probably carries down through the years.
Minorl's SP-11 now sits in my system deep behind the Orange Curtain (South Orange County, CA) and I remember listening to his system a few years back when he was kind enough to do an A/B session to help me in my decision making process. The SP-11 held up very well against his Ref 3.

I use the SP-11 quite extensively now, but I do prefer my SP-10 mki for analog playback (60% of the time) and the SP-11 for digital playback (remaining 40%). But then I get my jollies moving power sources and front ends around every 3-4 months (not!). If there was a way to extract the best of both preamps and cram it into one, I'd be in audio heaven...

Elizabeth's adventure with her SP-15 is intriguing and I have never had the oppportunity to audition one. That would be a fun listening session, an SP-10, SP-11 and SP-15 shootout.
I've worked on both the SP-11 and the SP-10 extensively. The SP-11 is probably a bit quieter in the phono stage then the SP-10. Both are marvelous preamps. Both bench test very well. Before comparing a new preamp with a rather old preamp one would have to recap the old preamp. That way you are comparing apples to apples. After 15-20 yrs, both preamps should be recapped before any serious listening comparisons take place.
I agree with Hifigeek1. I have been using SP-11MK2 for a few years now. I bought it here from the original owner, who re-tubed it about 10 years ago. I thought it sounded great.

Then, about a year ago, I started hearing the signs of a frying resistor in one channel. I took it in to the shop where they fixed the issue, replaced a few other things that were drifting out of spec, and replaced all the old power caps.

I then retubed it with the new Genelics that just came out recently. Holy cow! What a difference! I should also note that the repairman was amazed at how quiet the phono stage was.

Will it compete with a new $20K preamp? Probably not. However, I've had notable HiFi shop owners talk me out of replacing it with something that was $8K. He also mentioned that it would be a waste of money to spend $2500 on a stand alone phono stage. (I found a great dealer ;-)

Anyway, just my 2 cents. I'm sticking with the Sp-11 now that it's been rebuilt a bit.
The SP-10 was the last full-on tube preamp ARC made and was the zenith
of its 'old' sound. I owned one for many years, and its phono section was
glorious for the time period. A good clean example that has been brought
up to spec is probably fine, but it will be noisy as a phono preamp. I had a
devil of a time, back in the day, finding tubes that were not microphonic.
It was, and still is, a classic, much like the original SP 3 (which I also
owned, way back in the day). By today's standards, both are old school and
the SP3 would probably be considered very colored (it's been a long time
since I heard one), but in its time, it was a revelation, compared to
everything else.
But... since you asked about the SP-11, at the time, lot's of folks upgraded
from the 10 to the 11. The 11 was probably far quieter, but lacked the
warmth and rounded 'old school' tube sound of the 10. I think that this
actually stimulated the market for the SP-10 (at least the mkii, I never heard
a mk i). The 10 is a classic, in large part because of the sound it
represented. ARC seemed to go for a more modern, less 'tubular' sound
after that. Interestingly, the 'Ref' level stuff that ARC makes, in the form of
separate line stage and phono stages, seems to have gone back to tube
rectification and/or regulation. I just took a quick look on the ARC site, and
the preamps with integral phono stages all seem to be hybrids, following in
the path of the
SP-11, rather than the 10.
A low output MC would be a beeyoch on the SP-10. (Believe me, I tried
when I finally switched to horns, I had to get rid of it, it was just too noisy).
But, with low efficiency speakers and a higher output cartridge, my money
would probably be on the 10 (and i think they command a premium
compared to the 11, although I'm guessing- haven't looked at market prices
for these in a long while).
Bassphil..I know. I've recapped and re-tubed quite a few of those. Amazing isn't it??? lol
Can't remember what tube is used for the 11, but i started experimenting with the NOS tele in other gear, and it made a dramatic difference compared to other highly regarded tubes, holographic, without sounding too euphonic.
That preamp uses 6922's.
Thanks, Geek. My tube rolling experience was with the same tube type in a Steelhead, so having tried Mullard gold pins, Siemens NOS and Tele NOS, the Tele was by far the best sounding tube= holographic mids, but not lush sounding. Granted, the circuits are no doubt different, but to the extent one could extrapolate, the Tele made a dramatic difference in the sound of my phono stage.