Dear Joeb if you're running the Audio Research LS-15 on balanced your inout imedance on the Pass X250(certainlya wonderful amplifier) will be 22 KOhms.
in Rca single ended will be 11KOhms very small and that's why the impedance missmatch you're getting no bass extention on the very bottom and possibly soem top end issues as well.
Either keep the LS15 and sell the Pass adn buy soemthing like a Audio Reserch Classic 120 or 100, or some other tubes .. or keep the PAss, and replace the preamp by something like a transistor preamp if you still have your classé preampo you might want to try it and see what it does.
my recommendation if you can find an oder T-2 or T-3 Threshold preamp, form the early 1990's they are suberb and they drive anything from 600 ohms up, also Krell and Mark Levinson preamps will drive the Pass with aplomb.
The B&W's are somewhat power hungry but 60 to 100 watts of good tubes will drive them nicely too.
Another thing is you could go all tubes, find an Audible Illusions L-2 (remote controlled thank God!!) do the wheezer mods for about $1K end up with a $6,000 sounding preamp that will beat anything short of a CAT preamp including teh AR's and CJ's, and put the rest of the money on a chinese made tube amplifier (run them with a Variac into 110 Volts very important), por the rest of the money in the bank, take a cruise, go to more concerts, etc. etc.
maybe even silver cables, you'll love those on tubes, kimber, PSC, and others will sing in that system.
in Rca single ended will be 11KOhms very small and that's why the impedance missmatch you're getting no bass extention on the very bottom and possibly soem top end issues as well.
Either keep the LS15 and sell the Pass adn buy soemthing like a Audio Reserch Classic 120 or 100, or some other tubes .. or keep the PAss, and replace the preamp by something like a transistor preamp if you still have your classé preampo you might want to try it and see what it does.
my recommendation if you can find an oder T-2 or T-3 Threshold preamp, form the early 1990's they are suberb and they drive anything from 600 ohms up, also Krell and Mark Levinson preamps will drive the Pass with aplomb.
The B&W's are somewhat power hungry but 60 to 100 watts of good tubes will drive them nicely too.
Another thing is you could go all tubes, find an Audible Illusions L-2 (remote controlled thank God!!) do the wheezer mods for about $1K end up with a $6,000 sounding preamp that will beat anything short of a CAT preamp including teh AR's and CJ's, and put the rest of the money on a chinese made tube amplifier (run them with a Variac into 110 Volts very important), por the rest of the money in the bank, take a cruise, go to more concerts, etc. etc.
maybe even silver cables, you'll love those on tubes, kimber, PSC, and others will sing in that system.