mceljo These speakers you have are said to very similar in their impedance/phase graph to the 826 below,.
And this suggest very strongly, that both amps you are using especially the tube, Don’t have the gonad’s to be able to do these speakers justice, especially in the bass between 70hz and 200hz, where the impedance combined with the - phase angle will present a very hard current sucking load to the amp.
https://www.stereophile.com/images/archivesart/1110Focfig1.jpg
Cheers George
And this suggest very strongly, that both amps you are using especially the tube, Don’t have the gonad’s to be able to do these speakers justice, especially in the bass between 70hz and 200hz, where the impedance combined with the - phase angle will present a very hard current sucking load to the amp.
https://www.stereophile.com/images/archivesart/1110Focfig1.jpg
Cheers George

