As I mentioned earlier, the original KT88 tubes were impressive but I wanted a little more warmth and better bottom end. I have always had a soft spot for the 6l6 family of tubes. I told a friend of mine about wanting to try some tubes. He had a few sets of tubes in the 6l6 family that didn't suit his taste in his Elekit amp so he sent me his rejects lol. I ordered an EH 5u4g to get ready for them.
First up was a pair of 807 tubes with adapters. I had always wanted to hear 807 tubes so I was excited. They were unlabeled. My friend thought they were supposed to be Brimar but speculated that they were actually Russian tubes made in the 80s. They were dreadful. Thin sounding, screechy, and generally unpleasant. I told my friend and he said yeah, they were pretty much the same in his amp. I threw them away they were so bad.
The other set were much better. New Russian Golden Lion KT66. These had more of the warmth and "tone" that I was looking for. Now we were talking! Everything had more weight and sounded more natural to me. My opinion was further solidified once I replaced the GE with a 7n7 (see fist post).
I was happy with the sound but couldn't resist the siren call of trying other tubes in case they sounded better....
New Russian TungSol 7581a tubes slightly improved on the things that were important to me. a little better bass, little better guitar tone. Plus I felt comfortable using the 5ar4 with them for a bit more power.
I also ordered some new TungSol 6v6 tubes. Had heard good things about them. I wasn't too impressed with them. Pretty meh to me so I gave them to a guitarist friend of mine.
My friend felt bad about offloading his reject tubes on me and so ordered some 807 tubes from TubeDepot for me. Turns out they screwed up the order. He ordered the tubes he liked so much, Sylvania 5933. What they sent looked like proper 807 tubes (tall and curvy instead of short, straight, and squat like 5933). I had no idea they were the wrong tubes. They didn't have a manufacturer but were labeled CV 124. Ooh British! Were they Mullards? The 5u4g went back in and I fired them up. They certainly sounded like what I had assumed Mullards would sound like, big, warm, lush... I was in love!
Digging around I figured out they were Ferranti tubes. Also a British supplier, but it looks like these were actually Russian tubes. I think these are a screaming deal. You can get them for $15-$25 a piece. Well worth it if you like that kind of sound. Plus, they look amazing
Time goes on and my friend asks me if I'd be interested in some more of his "rejects" lol. His amp can take various tubes and I was benefitting from his experiments. This time it was the 6ar6. I had always been intrigued by these so was happy to try them out. Another winner! They resemble the 807s to quite a degree which shouldn't be a surprise. While they don't look nearly as good as the 807s they have better bass so they because my new standard. Keep in mind that even those these are octal tubes they are not plug and play! You need adapters in order to use them in the amp.
By this time I had been scouring ebay and tube sellers for more of those 807s, new input tubes, and now more 6ar6 tubes. I saw a pair of black glass Ken Rad 6v6gt tubes and ordered them on a whim. These sounded quite a bit better than the TungSol versions to me. Better bass, better depth, batter timbre. Still not as compelling as the 807 or 6ar6 though.
Once again my friend offered me another tube to try. This time they really were Mullards. I had never heard of the el38 before but wow, what a tube! First of all they are just sexy looking tubes. Still curvy like the 807 but taller. And they have the most prominent blue glow of any tube I have ever seen! But the real story is the sound!
In my amp, with the tall 7n7 input tube, and my speakers, the el38 gives me the best, well rounded sound of anything aI have heard so far. It has the clarity of the kt88 but better defined, possibly deeper bass than the 807/6ar6. The better details make the soundstage deeper. It's an impressive tube. It impressed me enough that I promptly bought out the rest off the Mullard branded supply of a UK tube supplier. I'm trying not to go into full on hoarder mode with this tube. I have never been this obsessed with a tube before, and that's saying something...
I prefer the 6ar6 when I want to rock out and the el38 for everything else. Man, I love this amp so much! So much fun!