Benchmark LA4 vs Linear Audio Tube microZOTL Preamplifier (Level 2)

The MicroZOTL Level 2 arrived last week and I have spent the better part of three days doing critical listening comparing it with the LA-4.  Right out of the box the MicroZOTL (MZ) was a bit disappointing.  The music seemed a bit more muddied (I know, what a wonderful audio descriptive word).  I let the MZ run for a few hours with me out of the room and when I returned the music was cheerful and enjoyable.  

That is when I started the critical listening.  As a rule the MZ was providing a wider soundstage with slightly improved instrument separation.  One thing that definitely improved in these early comparisons is the soundstage and instrument height.  The LA-4 provided an unnatural separation in height with some instruments/vocalists elevated above the soundstage plain.  This is welcome on some music (Pink Floyd's Dark Side of the Moon), but not with quartets or Santana.  The MZ does a great job when the sound should be elevated (some drum kits).  I like the improved instrument placement of the MZ.

After I decided I liked the MZ better than the LA-4 with Qobuz (through Innuos Sense) I started the test again with vinyl, then CD.  It was clear right away that the MZ was right for my system.

Then I started the test over with Qobuz and utilized the Bricasti M1S2 filter options.  My preferred filter was the Minimum 2 (M2) with the LA-4, although I would use the M1 and the Linear 1 (L1).  During my DAC comparison I found the L1 filter most resembled the Chord Dave DAC (extreme detail, almost clinical), and the M2 resembled the Mola Mola Tambaqui (most musical).  With the MZ the M2 is extremely musical and pleasant, but maybe just a touch less detailed than I want.  The L1 and M1 settings both work well with the MZ.  I have not decided which I prefer.

The upgraded tubes from Linear Tube Audio will arrive later (on back order) and I am looking forward to improvements they may bring. 

I was initially planning to keep the LA-4 and the MZ while utilizing a Transparent Selector from Pine Tree Audio and enjoy both pre-amps.  Plans have changed.  While the LA-4 is an outstanding line amp, I no longer need it and will be selling it soon.  The Linear Tube Audio MicroZOTL Level 2 pre-amp will be my long-term solution now that I have stepped into the dark side of tube audio.

@robshaw I was concerned about the lack of Balanced output from the MicroZOTL Level 2 but my cable runs are quite short and the LTA team maintains the RCA link is equal to the XLR (there is a balanced input available that I utilize for the Bricasti DAC input).  Additionally Pass Labs designed the XA-25 without balanced XLR inputs.  I saw that Nelson Pass felt the XLR was not needed for the amp.  I run a XA-25.  

I did run the Bricasti into the MicroZOTL with RCA and XLR and could not tell the difference.  I stayed with the XLR since I did not have another quality RCA pair to keep in  place.  Why spend $ when I don't have too.

All things being equal, my gut says the XLR option should be choice.  However, the RCA option from the MicroZOTL to the SPL Crossover, and from the SPL Crossover to the Pass Labs XA-25 is working great.  I am not going to sweat it.

However, if Pass Labs releases a mono-block version of the XA-25 with XLR input, then I may need to reevaluate my decisions.

I let the MZ run for a few hours with me out of the room and when I returned the music was cheerful and enjoyable.  That is when I started the critical listening.

That’s not nearly enough time for the preamp to burn in unless LTA did considerable burn in before it was sent.  I’d give it at least 100 - 150 hours before making any firm conclusions as it’s likely to sound even better with more hours, but that you still preferred it to the Benchmark after so little playing time is very encouraging (but not all that surprising IMO).  Hope the better tubes bring you even more goodness.  Enjoy!

@soix Thank you for the note.  LTA does some burn in prior to shipping, but also recommends 50 to 75 hours of additional time.  They also have a 30 day at home trial period, with the caveat of keeping the unit for a minimum of 14 days to insure the proper burn in is achieved (my guess).

I have just over fifty hours with the MZ so far.  If there is improvement over the current results, then "Yippee!"  

@thriftyaudio I will be interested in your thoughts on the upgraded tubes.  What tubes are in it now?

I've tried a number of 12AT7 tubes and there are big differences in sound quality between the different tubes.