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

@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. 

@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.