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

I’m very happy with my LTA MicroZotl level 2 preamp. I’m using it with a Coda No 8 amplifier.

I bought my LTA lightly used from a guy that moved to a high dollar integrated amp. He had upgraded the tubes to NOS Telefunken ECC801S. I experimented with several other tubes including the ones that he said came with the preamp. I did not like the tubes that shipped with the preamp. I’ve tried NOS Siemans ECC801S which are very nice and less expensive. Brimar Yellow T are warmer sounding and should be available from Tube Depot. In my system, I prefer the Telefunken, but would be happy with the Siemans.

@thriftyaudio I think you'll like it.  I had two different conrad-johnson preamps before the LTA and I prefer the LTA.

I'd be curious to hear which tube types you try and which ones you like. 

@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. 

@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 What have you chosen as the best tube combination for the LTA preamp? 

@thriftyaudio  I'd like to try the Ray Reserve, but I think I have decent tubes, so I can't bring myself to spend $480.  My tubes aren't the tubes that came from the factory with the preamp.  I tried those and they weren't as good.  

Did you have to buy a top with the bigger holes?  I looked at those, but LTA is sold out, so I don't think the Ray Reserve would work unless I left the top off. 

@thriftyaudio The Ray Reserve are 6SN7, correct? Did you try 12SN7?

Mine are 12SN7GT.  I haven't tried 6SN7. 

@thriftyaudio I’m using Telefunken ECC801S for the input tubes. I’ve tried a number of 12AT7 and equivalents. I like the Telefunken best. Siemens ECC801S were a close second. For my preferences.

I have ordered some tubes from a guy that sells on ebay. He’s knowledgeable about the LTA preamp and what works well in it. I asked him what he recommended for the output tubes if I’m looking for detail and clarity. He suggested Raytheon 6SN7 VT231 from the 1940’s. He also recommended trying GE 12SN7GT, and RCA 12SX7GT. They weren’t crazy expensive, so I bought matched pairs of all three. I really haven’t experimented with the output tubes much, so it should be interesting.

I received the three sets of output tubes that I mentioned earlier.  The Raytheon 6SN7 VT231 from the 1940’s are the best.  All three pair sound good. I'll be using the Raytheon moving forward.  I ordered a second set to have on hand.  $200 for the pair. 

After running the Raytheon 6SN7 VT231 for a while, I felt like some of the sparkle was gone.  I had a pair of 50s Sylvania 12sn7gt bad boy that I hadn't tried since I'd made some system changes, so I popped them in.  The magic is back.  Those along with the Telefunken ECC801S seem to be the best for my tastes.

Filled a box with tubes before reaching that conclusion.  Lol.