Input impedance issue?


Hello all,
I have a PrimaLuna Prologue Premium power amp driving KEF LS50's and a Rotel RB-880 power amp driving 12" NHT subs.
I'm using an NHT X2 crossover on the subs and going direct on the KEF's. I don't like the sound I get on the KEF's going through the high pass on the NHT. They are both being driven by an Audible Illusions L1 preamp. The pre has 2 sets of outputs. Seems when I have one output connected to the NHT and the other to the PrimaLuna the high end on the KEF's drops off. It's there but no sizzle. The only way it seems to sound right is to connect to the NHT via the tape outs on the pre for the subs. Then it's kind of a pain to keep moving the level on the subs all the time. Does any of this make sense? Any ideas? Thanks in advance.
Ben
honashagen
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I'm using an NHT X2 active crossover on the subs.It has a high pass output but when I use it the KEF's sound less detailed. A better active crossover would probably cure this too. Bryston maybe.
"I'm not sure if the Musical Fidelity buffer (the X-10v3 I believe) is still being made, but if you can find one it would be a good solution. Also, another member here who had a similar issue has reported an excellent experience having a tube buffer custom made for him by Tom Tutay of Transition Audio Design, in Florida I believe."

Since this will be used only for the low frequency signals going to the sub, isn't there a solid state solution that would work? People seem to buy these tube buffers for the sound of the tubes themselves. That's not the case here.

"09-30-15: Honashagen
I'm using an NHT X2 active crossover on the subs.It has a high pass output but when I use it the KEF's sound less detailed. A better active crossover would probably cure this too. Bryston maybe."

I wasn't exactly clear reading through your original post yesterday. Are you going from the pre outs on your AI directly to your Primaluna amp? Or are you going from the AI to the high pass input on the NHT, and then to the Primaluna? If you are going through the NHT, you have to consider that xover will most likely undo any sonic benefits your preamp has to offer. I assume that if you just leave everything involving the subs off, and use the AI, PL and the Kef's only, you get good sound quality?
ZD, yes, a suitably chosen solid state buffer will of course do the job well, and perhaps (depending on the specific models being compared) better than a tube-based buffer. But a tube-based design that is intended to be used as a buffer perhaps stands a greater chance of providing an optimal combination of high input impedance and low output impedance, especially the high input impedance part.

Burson Audio used to make a well regarded solid state buffer, the AB-160, which may be findable pre-owned. I am not specifically aware of any other high quality equivalents that are currently produced, but there certainly may be some.

And hey, perhaps a good solution would be to simply buy a used minimalist/no frills solid state or tube line stage preamp, which provides high input impedance and low output impedance, and insert it between the existing preamp and the NHT crossover.

Best regards,
-- Al
Any other suggestions on buffer amps? $350 for the Musical Fidelity! Ouch. What about the tube buffers from Yaqin? Any other recommendations?