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

@yyzsantabarbara I was hoping you would contribute.  We seem to have similar tastes in audio.  I am hesitant to try a different DAC since I just purchased the Bricasti M1S2 a few months ago.  I compared it directly to a Chord Dave with M Scaler and a Mola Mola Tambaqui (both in my system) and the Bricasti was the clear winner.  Even used it was a bit expensive so I want to hold onto it and enjoy the music.  I like the various filter options it provides to match with recording productions.

@audphile1 thanks for the recommendation.  I have tried the M1S2 without a preamp in line, but the sound became muddled at higher volume.  The LA4 does a better job with the M1S2 than the DAC does by itself.  I am holding out hope that Pass Labs will release a dual monoblock version of the XA25.  I will definitely upgrade the power amp for them!

@zlone thanks for sharing your experience.  I really wish I had found a used XP22 to try in my system.  Maybe I will find one in the next few weeks to compare with the LTA and Benchmark.  The added benefit of a Pass Labs preamp would be the ability to turn the XA 25 on/off with the remote.

@sls883 ​​@bluethinker I have heard nothing but praise for the MicroZOTL Line 2 form several sources.  I have a new one on its way with three sets of tubes (standard plus two different upgrades tubes).  I will not be purchasing additional tubes for this comparison, but I will try all three sets of the supplied tubes.  It should be fun!  

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

@bluethinker ​​@sls883 The three tube types are "stock tubes" plus

• Free Premium Tube Upgrade: Receive a FREE Gold Lion + Ray Reserve 6SN7 tube upgrade with your MicroZOTL Preamplifier purchase

• as part of the 2024 holiday deals.

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.

@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!"  

@robshaw Hi Robert.  My Acoustats are inefficient speakers (83 db) and do not generate exceptional bass.  When I first purchased the speakers I added a Vandersteen 2W subwoofer that supplemented the bass and that was a good solution for many years.  A few years ago I wondered how the Acoustats would do if they did not receive any (or essentially a minimal amount) of the bass signal. 

I replaced the Vandersteen with the dual Rythmiks and inserted an active Crossover which limits the signal to the Accoustats (currently at 70 Hz) and the Rythmiks (same 70 Hz).  This helped the main speakers substantially.  The folks at Pass Labs suggested this changed the Accoustats efficientcy from an 83 db to 89 db which allows the XA-25 to effectively drive these power thirsty speakers.

The crossover I utilize is an excellent unit from Germany.  The SPL Crossover allows me to adjust the crossover on the fly, adjust the signal slope, and many other fun tidbits.  Another one I considered was the JL CR-1.  I believe I would have been happy with either (similar concept with a few different options).  The SPL I purchased was a demo unit and I got a great price.  

Sorry I can't help with the LA-4 solution.  An active crossover may be your best option.  There are less expensive active crossovers available, and a few significantly more expensive.  My research suggested the JL or the SPL units would be ideal for my system.  An active crossover might help relieve some of the bass demand from your speakers resulting in a clearer mid-range.

Best of Luck.

Ralph

@robshaw I truly understand.  While I am retired, I am active in two groups (one Board), plus creative writing, woodworking, and honey-doos.  It keeps me busy.

The addition of the SPL Crossover is perhaps the single biggest improvement for my system.  The bass extended and the total sound improved significantly.  I occasionally make bass adjustments depending on what I am listening too.  There is nothing like listening to the 19812 Overture with canon and having the bass turned up and over emphasized!

If you could swing it you might want to look at this JL CR-1.  I did not see any SPL Crossovers available used in the US.  I highly recommend an active crossover if you have dual subs (or more).  

https://www.usaudiomart.com/details/650175851-jl-audio-cr-1-crossover-free-shipping-in-conusa/

I have listened to the Ray Reserve tubes for the past week. The improvement I heard from the LA4 to the LTA MicroZOTL was matched by the improvement with the RR. Still waiting for the Gold Lion to arrive. It sounds like LTA will be offering Ray Select either in place of, or with the Gold Lion. I am hoping there is some change, but I cannot imagine what it would be. The good thing is I will have back up tubes in case anything fails.

Only two things on my upgrade list now.

1) Monoblock Pass Lab XA025 amplifiers.

2) Innuos NG item to replace the Pulse and Phoenix currently in place.

I am always concerned the Acoustat 1+1 will reach the end of life (close to 40 years old), but I will cross that bridge only when I absolutely have to. The entire system is built around the Acoustats!

Installed the Gold Lion tubes a few days ago and let the system adjust. Performed the critical listening test tonight. I was expecting little or no improvement. The first few passive listening sessions were a bit of a disappointment.

Started off with some classical and went, ’wow.’ I thought it might just be my music selection. Moved onto a quartet with Vivaldi and was also impressed. Pushed on with Santana, then Horslips, and finally some good ole Three Dog Night. I am stunned. This pre-amp, in my system, sounds amazing. Just to push the sound a bit I tried some Stray Cats. Nirvana... today. Probably tomorrow too!

I was getting ready to upgrade the streamer to an Innuos NG product, but that is on hold. I am at a satisfaction state. It is best that I hold onto this for awhile. It is nice.

@sls883 Thanks for following up.

The folks at LTA are correct with the Ray Reserve and the Gold Lion tubes being a step up, or three, over the stock tubes. The RR tubes were a huge upgrade and I was already pleased with the improved listening fun of the MicroZOTL Level 2 over the LA4 (which is a great SS amp). The Gold Lion tubes just added a bit of detail and a bit more 'smoothness' to the experience. 

I asked LTA about the Ray Select tubes that are the same size as the Gold Lion. It sounds like the RS tubes MAY become an option at some point. I am tempted to get a pair, but will wait.

The next step on my audio journey is adding a Network Switch. I was considering an Innuos Phoenix NET, and during my research found the Network Acoustics Tempus. I reached out to them and asked what kind of improvements would my particular system experience. The response was the typical 'background blackness, detail, soundstage improvement, etc'. They did suggest I try something first to confirm the benefits of a network switch. 

we recommend trying a d-link dgs 105 with an ifi power 5v psu.

It was an interesting suggestion since they suggested it would be around $70 US. It ended up costing just under $100, but still a lot less than a used Phoenix USB or used Tempus. I will be installing the switch this week.

The hobby is definitely fun, and not always uber expensive.

@sls883 LTA sent the Ray Reserve and the Gold Lion. They were part of the holiday special pricing. The RR tubes are big, but fit in my system. They poke out the top. The holes are quite large on mine. Ask LTA. I am sure they would help.

@sls883 LTA sent 6SN7. I have only used the tubes LTA shipped. This whole tube thing is new to me.

@sls883  May try the Ray Select 12SN7 tubes. 

@yyzsantabarbara Thanks for the question. I always value your observations.

The LTA with just the base tubes was an improvement over the LA4. May have lost a touch of the high end, but on the whole the details were essentially the same with improved soundstage. With the upgraded tubes (Ray Reserve and Gold Lion) the high end details matched the LA4 and the soundstage improved some more. 

I liked the LA4, but the MicroZOTL Level 2 match it in details while improving soundstage and separation. I find the LTA is on much longer during the day with me and with my wife. No regrets.

I have a question for you regarding Network Switches. Do you have any experience or recommendations with them. Recently added one ($100 total with d-link dgs 105 with an ifi power 5v psu) as suggested by Network Acoustics (Tempus) as a trial run. I liked the change. Trying to more research before making the plunge.

@bluethinker I agree. I have reached out to them regarding a couple things. Never problems, just curious questions, and their responses have been timely, pleasant, and extremely helpful. If I wasn't so happy with my Pass XA-25 and my Bricasti DAC, I would definitely consider LTA's offerings. They look intriguing. 

Thanks for your response @yyzsantabarbara .

I tried a fiber conversion roughly 18 months ago and found it slightly inferior to USB into an Eversolo. I also tried I2S into a PS Audio DAC and was disappointed with the results.

My conversion connection for the fiber was not high grade, but it was highly rated. I may investigate further since my current system is significantly better.