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

@sls883 it will be interesting to get your thoughts on the tubes.

The 12AT7 that came factory in mine were branded Trigon.  From what I was able to learn, they are probably a rebranded something.  They aren't great. 

I have Sylvania bad boy 12sn7gt and RCA 12sn7gt. I don't recall which pair is installed. 

"Maybe I will keep the LA4 and switch back and forth."

Great choice. Get another preamp for variety. If your power amp has a front facing switch to toggle between RCA and XLR inputs, then you can even have 2 preamps hooked up at the same time. You need to see if your Bricasti is good with having the RCA and XLR outputs connected at the same time to 2 different preamps. In my office, I have my Yggi+ OG DAC connected to 2 preamps and a tube headphone amp at the same time.

BTW - My Schitt Yggi+ OG was compared this weekend to the Dave and the Tambaqui at a pretty cool headphone event. I was not there but I got feedback that both DACs were slightly favored over the OG.

"The LA4 does a better job with the M1S2 than the DAC does by itself."

I found that all DACs I had in my system were better served by the volume on the LA4. The only one that came close was the Lumin X1 that has a special Leedh volume control. Even that had a slight gremlin at the lowest volume levels.

As A said in a previous post. I own 2 LA-4 preamps, Love them, my system is all balanced. Rock and Roll, great electronics (in my opinion, ex: Pass X250.8, Bricasti M1SE) Nice feature, adjustable gain, and I run my 2 SVS Sb4000 subs via a split balanced cable run out of the rear mono stage of the LA-4  Just my $02. Robert TN

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.