I am finally getting around to providing an update on my horizon. As some of you know, I am functionally blind, and my right arm is in a sling from shoulder surgery so if there are grammatical errors, so be it.
I received my Horizon in October and I have played with the same tubes that were provided to me from Lampi. I did not change any tubes for the first two months as I wanted to get a feel for the sound of the H.. The tubes that were provided are as follows:
KR KT88
KR 5U4G
Sylvania VT99
In December, I purchased the Aries Cerat Essentia mono amps. These amps replaced my Canary Audio grand reference 300 B mono amps. When you have 16 western electric 300 B tubes the sound is definitely different. Each amplifier has its pluses and minuses but I am happy with what I have.
While I am an audiophile, I am not up on all of the terms that I generally read about on this forum. So for me, it really is a matter of what my ears hear and what I enjoy listening to.
For the last 25 days, I have been doing a lot of tube rolling, and will provide my feedback below. The first tube I changed was going to a Aqua 274B from Sophia electric. As I stated in a post up above, I could not believe that a rectifier could provide that much improvement and sound quality, but it did for me.
I made a mistake with the next tube that I rolled in because I knew it would be good. I added the BRIMAR yellow T 6060 tube. This tube might be one of the best 12ATZ tubes on the planet.
Lastly, I added my secret weapon in the 1959 TUNG SOL NOS 6550 pentode tube. After adding each tube, the sound just got better. This will be my go-to pentode tube forever.
I said I made a mistake by starting with the 6060 tubes because I had numerous other tubes that I wanted to try. All of the tubes that I am using are all NOS from the 50s and the 60s. It should also be noted that I am running the Horizon in SE mode.
The next two tubes I tried were supposed to be better than the BRIMAR tubes. One was a RCA 5963 12AU7 black plate and the other was a GE 12AU7 Black plate. Both of these tubes are rare and not easy to find. Both of these tubes, unfortunately, did not work as expected in the H. They are very low gain tubes, and as a result, appear slightly grainy, and I need to adjust the volume to between 34 and 37 to get the same experience, as I did, from all of the other tubes at a volume control level of 30. I do not have a preamp in my system so I am using the H volume control setting.
My next tube was a RCA 12 ATZ black one half wing plate. It was definitely an improvement but did not compare to the BRIMAR.
Next up was the Toshiba, ECC 82 12AU7 Mullard equivalent. I liked this tube a lot, but it still was missing a little bit of bass for me.
The next five tubes I will mention all could be a triode that I could live with for the rest of my life and it was very hard to decipher differences in sound. I will start with the GE 12ATZ small round gray plate. This tube had a deep, clean base, it was very tight, clean, and fast. The vocals were really clear.
The Siemens ECC 81 was just a fabulous tube from the 60s era. It was German made and very high-quality. It was extremely close to the RCA that I just talked about above.
In the final three, the Sylvania 12ATZ shiny black plate was just magical. The sound quality and the soundstage were fantastic. It had punch, dynamics, and was clean, clear, and crisp with a very deep bass. I was able to pick up the micro details of instruments that others I did not. With this tube, it felt more 3-D. It had more of a forward sound. I would put it as an equal to the Brimar 6060.
When we were at Steve's house in February, Lukasz picked out another of my tubes which was the Sylvania 12AU7 shiny black plate. At that event, Lukasz thought that tube was better for him than the Brimar 6060 due to the better base. Unfortunately, my wife broke that tube when she was trying to insert it into the adapters so I did not get to listen to it but I have one coming so I will provide more feedback when it comes. I have a Woo adapter and I also bought another one from a company that I cannot remember. I would say the quality of the Woo adapter might be microscopically a little bit better, but there is absolutely no difference in sound.
Just to be sure of my findings, I went back to the Brimar 6060 yellow T and I felt the same that the Sylvania and Brimar were the two best tubes in conjunction with the 274B and the TS 6550.
I had one more tube to try that I knew nothing about and it was a BRIMAR 13D9 tube from the 1960s. It is a black plate designed for piston engines and airplanes and field surveillance radios. It only took 30 seconds for me to say, so far this is my endgame tube. The bass was outstanding. It was fast, and the vocals were soulful and distinct. It had a major punch. I could feel the stage presence of a live concert. I think part of the reason that it performed better than all of the other tubes was that it was a higher-gain tube, and it just had more power. I was told that this tube is a much later version of the 12ATZ tubes and that they measure far above normal NOS specifications for that time, which is considered to be the late 60s.
Every tube that I tried was an excellent tube. I think the main difference, in reality, is there are gain differences between 12AU7 and 12ATZ. I just like tubes with higher gain.
If there are one or two other tubes that I should try, please advise. I am not a tube roller and the only reason I did this was that my shoulder is in a sling, and I had nothing else to do. I will be happy with my combination of the Brimar 13D9, TS 6550, and the Sophia electric 274B aqua.
During this whole testing process, I kept the volume level at 30 and played the same group of songs which I can tell you now my wife is sick of hearing. The majority of these tubes have not ever been discussed in this forum so in a small way I hope this helps.