LTA Ultralinear vs Pass Labs XA25

I'm very curious if anyone as listened to or had the chance to AB test these two amps together? I currently own the LTA ZOTL 10 MK II and absolutely love it for a multitude of reasons. I'm in the market for a new amp because 10 watts isn't quite enough power to drive my 88db SALK HT2's. I'm almost ready to spring for a Ultralinear but am very curious about the Pass XA25.

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I have the Xa-25 so have researched the threads regarding that.  If your primary music is rock, consensus is go Xa-25.  As far as power goes, your 4 Ohm designed speakers with the Xa's output of 50 Watts class A at 4 Ohms might be a better match.  Room, music and playback volume etc. aside.
Srajan at 6 Moons started reviews on both. Im looking forward to his comparison. 
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. 
I am also addicted to the LTA sound. That zotl40 has got to be incredible. 
I am also addicted to the LTA sound. That zotl40 has got to be incredible.

Agreed. I’ve had other amps in my system like a Rega integrated and PS audio M700 monos and nothing comes close to the clarity and detail and vivid tone of the LTA.


Al clearly made  a very sound case for why the Pass XA could be a successful pairing with your
Salk speakers and I suspect this would be a terrific sounding match with no concerns about power and current.

It is quite apparent however that you are highly impressed with
thpe sound quality of the LTA amplifier. As was suggested above the ZOTL 40 REF may be the better LTA option for your specific speaker. A direct comparison of the XA25 vs ZOTL 40 in your system would be an ideal circumstance.

My belief is that both of these amps will sound quite good but with very distinct sonic signatures.


I own both LTA amps. The ZOTL40 Ref with the latest upgrades is every bit as good as the Ultralinear. Both are incredible amps. Also, the ZOTL40 is great if you like to tube roll. I have not heard the Pass XA25 but I would love to.
Thanks everyone! I’ve ordered the pass Xa25 and will post my impressions here as I begin to listen. I’m so curious to hear it next to the LTA


That's an excellent decision! There's simply no better way to judge an audio product than to hear it in your own audio system. Granted,  easier said than done sometimes. I look forward to your listening impressions.


The XA25 arrived this afternoon and my very early impressions before breaking it in are that it sounds very detailed, sweet and MUCH more dynamic. I assume this is because of the fact that the ZOTL 10 was struggling a bit with the Salk’s 88db efficiency. I’m very psyched so far. I assume the soundstage will open more as it breaks in but it already sounds layered and wide. More to come when I listen in depth over the next days. Stay tuned.
I've got both right now driving a pair of Tannoy Eaton's (89/8). LTA reference pre in front w/ a Rockna Wavedream DAC. 

Can't go wrong with either. I personally prefer the XA25. More detail, faster, more spacious, dense images. Extremely transparent. 

The UL has a boogie factor that is incredible. Really captures the emotion/feel/touch of a player well - especially during a solo.  UL also has a little sprinkle of inner tube glow which is great.