Audio Research

the second version was a nice, low cost upgrade...I had mine upgraded by ARC then moved to the LS25mkll which I liked a lot better...

Rather than buy an old used Audio Research, why not try something like the Schiit Freya for $699?  It is balanced, tubed and if it is as over achieving as the DACs, should sound extremely good. 

http://www.schiit.com/products/freya

 The Audio Research LS25 mk2 is a real jem. I had one for a number of years and was only convinced to upgrade when I heard the Ref 5se. The LS25 mk2 holds its own really well against most current preamps. That is were I would go. The LS15 is a bit dated at this point.

I’ve been using the same Audio Research pre for about 25 years, and that isn’t for lack of trying at anything resembling a sane price. LS17-SE, LS27 .. dog meat compared to Filet Mignon. What is it? An Audio Research LS2 B MKII with remote volume/mute. A pretty good preamp with the AR standard issue Russian or Chinese 6DJ8 which does not do it justice in any regard. About 20 years ago I started tube rolling it, Holland, Russia, US ... 6 DJ8’s, Bugle Boys, PQ’s, most everything until I stumbled on a Siemens and Halske Cca 6922 grey plate..... OMG. I picked up a few NOS spares, which are unobtainable today but even the best of them do fade in a couple of years since they are already 50+ years old and the vacuum is somewhat compromised on almost all. I have laid in a few Russian rockets and such.. from pre coffee memory 6H23’s which I have not tried yet but spec identically and I have seen a few reviews rating them with the Siemens. I also had a Valvo Cca 6922 pinched waist which was superb but also ,,, one or two years of light use. The point being, if you can find an LS2 B..(or an LS2 if you don’t want to run balanced) MK 1 or 2, it would probably be well under $1K and it is a monster performer well out of it's price class. If I find one somewhere I’m going to send it out and get it recapped and the power supply upgraded and see what that does.

 This is very curious. I owned an LS2 mk2 for a number of years in the mid to late 1990s. The B stands for balanced input.  It was good for it's time but it was never great. The LS25 mk2 I had after was in a totally different league. Just so much better in every way. Far more detailed and holographic without sounding thin. 

 I agree that the LS27 is not that great.. I had a chance to buy a demo unit at a great price and passed. It sounded thin and lifeless in my (all ARC) system compared to my LS25 mk2. Audio Research has had some real winners but then there are others that are just so so.