Prilaluna Prologue Premium with KEF LS50

Hello all!
I just purchased a used PrimaLuna Prologue Premium with stock tubes. It replaced a Sophia Electric Baby amp. The Primaluna seems to have a peaky upper midrange I can't seem to tame. I doesn't seem like I can see inside the music like with the Sophia. For example if a flute player takes a breath I can't hear it as well. I have tried cables with no luck. Any help?
Thanks in advance.
If you are presently using the amp's 8 ohm taps, given the upper mid-range impedance peak of the speaker, as shown here, going to the 4 ohms taps will probably reduce the peakiness of the upper midrange. Although it may also have other sonic effects which you may or may not prefer.

-- Al
It could be an artifact of using teh PL tube amp with the KEF ls50. The KEFs are not tube amp friendly. Look for measurements on teh KEFs. Impedance peaks and dips and/or pahse angles at various frequencies with the KEFs might produce teh results you hear. I would only use a high current SS amp with those speakers for teh best results.

I ran a friends LS50s off TAD hibachi amps I had that are designed to emulate a tube amp. The results were much as you describe. Same speakers then sounded great 15 minutes later running off high power high current Bel canto ref1000m monoblocks (Class D SS).

So I suspect teh problem is with the combo of amp and speakers and not inherent to either one alone necessarily.
Thank you both. I'll try the 4ohm taps. I want to love this amp.

If the amp is brand new, it may not be broken in yet.
It's used but I am not sure how old. Pretty sure it's broke in.
Maybe different and/or better tubes?
Change the tubes. Stock ones are not great
Turns out it is on the 4 ohm taps. Ant recommendations on tubes?
Try the 8 ohm taps.
The stock tubes may be doing the sound any favors. Lots of discussion about this, do a search. In addition Kevin Deal has tubes for rolling for sale, you can ask him for help with his amp.
Change the tubes. Stock ones are not great
Sorry for double post