2. amps-preamps
  3. 1443549764

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
zd542
5,339 posts
 
Your PrimaLuna has 4 and 8 ohm taps for your speaker cables. Try them both and see if it makes a difference.
honashagen OP
137 posts
 
I have and the 4 ohm taps work best.
koestner
636 posts
 
Put a tube buffer in between your preamp and the NTH crossover. The very high input impedance of the buffer will make it almost invisible to your preamp. I think the Musical Fidelity buffer in the square box has a 1 million ohm input imp. that you can pick up for around $200 or less. I noticed the exact same thing on my pre using both outputs, one to the main amp and the other to a powered sub. The tube buffer was my fix and I didn't get it for the "tube" sound, but rather as an impedance matching device.
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