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

@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. 

@thriftyaudio - I’m happy you are enjoying the LTA preamp. I really enjoy mine. The company is always a pleasure to interact with when I have questions, which is a nice bonus. 
 

Let us know how the preamp continues to burn-in and how the new tubes sound. I have not done any tube rolling myself, so I’m eager to hear how different tubes sound in the LTA preamp. 

to Thirftyaudio: I am very pleased to hear your so happy with the new tube pre amp. Let me know if you would be so kind, as to further improvements, etc. in sound as it burns in. I have never gone down the tube route. (enough rabbit holes exist)  Was always curious about the tube route though.

Just curious about your dual sub hook up to the MZ. Mine is currently split through a mono balanced choice of the LA-4. Not familiar with the rear layout of the MZ. Thanks, Robert

@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