Preamps for $300 to match with B&K st-140?


Im trying to get a little more warmth and power to my JM Labs Chorus 706's so I picked up a B&K st 140 amp. Now I need a pre to go with it. I want something under $300 that has a tone bypass, and maybe a phono input. Im going used so vintage is ok. Tubes are good too. Thanks for the help!
bundee1
Kool39, "the 10-100 times guideline" is some what arbitrary and IMHO generous. While 600 Ohms will probably work, it might require more attention to interconnect selection.
Would Audioquest Diamondbacks be ok with that combo? What cables do you suggest between them? Any other pre suggestions? A few people on other forums have suggested the bottlehead pre, anyone have any opinions on that piece? Thanks for all the help folks. With any luck the amp will arrive tomorrow.
I'm not familiar with the diamondbacks. I would suggest avoididng interconnects that are very high in capacitance if you use a pre-amp with a high out-put impedance into the B&K ST-140. Of course the length of the interconnect will have to be factored in.
I got the amp today and posted about it. I hooked it up to my integrated as a pre. The diamondbacks sounded awful. Im now using Synergistic Research Alphas between amp and pre. Im looking for a nice cheap neutral to mellow pre. I have my eye on a NAKAMICHI ca5a2 pre. I want a little more bass and clarity. Any other cheap suggestions?
How about an Adcom 565 preamp. These sell for between $200.00 and $300.00 used.Known for it's neutrality..it will probably do the trick.