So far I’ve owned the following amps for my Apollo 11’s, in this order.
LTA Ultralinear (mono and stereo)
VAC 30/30 III Signature
LTA ZOTL40 Reference
Allnic M2500 PX25 mono’s
Some were owned concurrently. All worked well, each with its own strengths, to different effect. I’ve used the LTA Preamplifier with all and more recently moved to an Allnic L9000 OTL/OCL preamp. DAC is Lampizator Pacific. Antipodes CX+EX server.
The XA30.8 excelled at stage width, HF extension and dimensionality, low end control. Weakness was midrange resolution.
The Ultralinear excelled at blackness, mid range resolution, HF dimensionality, bass definition, low volume playback. Weakness was dynamics as the volume increased. No gush factor.
The VAC is a romantic sweetheart. Decent bass and leading edge resolution for a tube amp. Old school 3D sound. Self noise not the best. Not as black as the best. Not as resolved as modern amps. But a really enjoyable amp. Hot.
The ZOTL40 Ref. More power and midrange compared to the Ultralinear. Typical EL34. Not as resolved or black as the Ultralinear. HF and bass extension not as good as UL. Full mid bass. System probably has too many tubes for this amp to excel.
Allnic M2500. Resolved modern tube amp with excellent PX25 bass. Nicely resolved harmonics. Low self noise, but not in the league of the Ultralinear. More meat on bones than UL or any other except the VAC. Nice mid bass balance makes an excellent match for the Apollo magic 10” woofer. Nice gush factor when played loud. Swells dynamically. Only 20 watts but they are clean and consistent up to max. Output. Best match to the Daedalus so far, but $$$.
Note that all are rated between 20w/ch and 40w/ch. But the Pass is a cheater that drives much harder than 30w.
My subjective ranking is:
5. Zotl 40
That said, I wouldn’t mind picking up an XA30.8 or Ultralinear again to add back to the mix.