LTA Ultralinear vs Pass Labs XA25

To add to Wlutke’s comments I would definitely not proceed with the LTA Ultralinear before asking Mr. Salk about the suitability of using an amplifier having a 1.6 ohm output impedance with your particular speakers. My strong suspicion is that the result would be weakness in the bass and mid-bass regions, as a result of the interaction of that output impedance with the speaker’s impedance variations over the frequency range. Especially if the impedance curve of the HT2 is generally similar to that of the HT2-TL, as shown near the middle of this page.

Also, keep in mind that 20 watts is only 3 db more than the 10 watts you are presently finding to be insufficient.

Also, as is the case for most such specs I suspect that the speaker’s 88 db rating is based on an input of 2.83 volts. For the speaker’s 6 ohm specified nominal impedance that corresponds to 86.7 db/1 watt/1 meter. For the 4 ohm impedance the speaker probably has in much of the bass and mid-bass regions, where lots of energy is typically required, it corresponds to only 85 db/1 watt/1 meter. For most listeners 20 watts won’t be sufficient with speakers having such low efficiencies.

Finally, it’s a bit disconcerting that the LTA amp does not have a specified power rating for a 4 ohm load.

BTW, FWIW I’m a very happy user of an XA-25. My speakers are Daedalus Ulysses, which have an extremely flat impedance curve, a 6 ohm nominal impedance, and a specified sensitivity of 97.5 db.  I listen primarily to classical music. 

Good luck, however you decide to proceed.

-- Al

Thanks so much Al. Those Daedalus speakers you have are pretty incredible. The ZOTL 10 that I currently have plays incredibly well at reasonable to low listening levels, it’s the best amp by far that I’ve ever heard on the Salks. I’m hoping that 3db 10watts extra of headroom with the ultralinear is enough to give it that little bit extra. But you’re right in that I should probably call Jim to make sure. LTA specifies that 88db is the limit for critical listening and low volume level listening is 85db. 

Paul I’d love to read the 6moons comparisons between the two. Very interested. 

As an extremely happy owner of the Ultralinear LTA I’d say Pass. The LTA UL was designed specifically to work magic with high efficiency designs like Al’s Ulysses and my Apollo’s. With speakers of this type it is off the charts. But matching amp and speaker are crucial so you would be ignoring this truth with the UL. I’d either go with the Pass or consider the LTA ZOTL 40 Reference, which I understand from Mark Schneider at LTA is now very close to the UL but made for less efficient designs. Maybe try both and see which you prefer. LTA has a very generous return policy.

Thank you very much! I‘m gonna do more research. The Pass is intriguing but it’s not as easily available to audition since their return policy isn’t as good as LTA. I have heard great things but at this point I’m totally addicted to the LTA’s sound. Might take your advice and go with the ZOTL40 ref.