It is a good idea to purchase a vintage tube pre-amp.


Since the new one are pretty expensive and what I can afford is an old one with budget of US$2000~3000. Since I don't have much knowlege on electronics, but I have authentic listening capabilities. Is it good idea to buy an old gear of tube pre amp. around 10 or 15 years such as Audio Research SP-15 or something similar (the newer one within my budget is better of course).  I would prefer a stable, long time use gear without much trouble.
128x128faust168
Another good bargain is the Doge 8. Which is about $1500 new. As I said earlier the Linear Tube MicroZotl2 is ridiculously good for the price. Terry London thinks it is outrageously good also and uses it in his reference system. I too had a bias towards older Tube pieces until hearing this preamp. I have had used Supratek, Thor, ARC sp 10, VTL Ultimate, CJ Premier 10, precision fidelity 7a, Doge 8 and others in the budget line all the way to the CJ Art 3 and the ARC Ref 5. The purity of the Linear Tube MicroZotl2 is just amazing. When you roll the tubes it is about as good as it gets. David Berning is obviously a genius! Oh that reminds me that reminds that I had the Berning TF 12 at one time also!
Looking at the listings now there are some awesome choices in your price range such as this:

https://www.audiogon.com/listings/tube-silvercore-transformer-coupled-input-and-output-tube-preamp-s...

this:

https://www.audiogon.com/listings/tube-audio-valve-eklipse-stunning-pre-amplifier-2017-03-06-preampl...

this:

https://www.audiogon.com/listings/tube-shindo-labs-aurieges-l-tube-preamp-mint-2017-03-15-preamplifi...

Just to list a few and many others just above $3K. If you are willing to look beyond the usual suspects, ARC, c-j, etc, there is a wealth of top notch used gear out there in your price range.  I absolutely agree with Swampwalker a good pre is critically important and can really transform the sound of your system!
Don Sachs upgraded my HK C-I and it was splendid, but his own preamp, mentioned above, is far better.  I have had it for a couple of years and with his latest improvements, it is peerless.  There is magic in 6NS7 tubes!!
Mark

The thing that always reminds me how subjective this hobby is is the variety of choices we have. I too have owned numerous preamplifiers and heard many times more in my set-up and outside. I am currently enamoured with a Conrad Johnson PV9a that has been upgraded with cutf vcaps bypassing the huge coupling caps, and numerous other upgrades that has taken this preamplifier to another realm altogether. Total investment including purchase price, less than 1.5k including a marvelous phono stage that is just so engaging.The soundstaging, dynamic shadings and timbral accuracy is stunning and an example of what can be accomplished with a well designed vintage product and upgrading parts.

The important thing in considering a vintage unit would include purchase price, condition and cost for upgrading to determine whether or not it is worth it. The big thing to consider is that if you can pick up a good vintage product like a CJ Premier 3, ARC SP8 or a nice 6sn7 based preamp with a good power supply, much can be done to improve performance and it sure can be worth it. I know a few guys that still use Marantz 7 preamps. Good design is timeless and better parts can realize significant improvements.