My favorite 6SN7 is the Sylvania short bottle chrome top from the 1950's. In my system this is the one that sounds best. I don't know why. I haven't tried the Brimar which, from what I have heard, is really, really good. I don't care too much for the Black Glass Ken Rad VT231. It has a muddy sound in my system. I also recently tried the Shuguang Treasure CV181 in my system and wrote the following mini-review of it in the "Reference 6SN7" thread:
"I bought a burned-in pair of Shuguang Treasure CV181s. As most of you know, they are a 6SN7 but shaped and named like a CV181, which, as we know, has too much heater draw for our purposes. I plugged them into my amp and I heard some very interesting things. These tubes gained a very good reputation thanks to reviews such as Mark Wheeler's at TNT-Audio. To make a long, somewhat long-winded review short, they were the best 6SN7 type he had ever heard. He focused particularly on the resolution and the inner detail of the CV181. But he also writes that it images better, has better dynamics (macro and micro), is faster, stronger, hipper, lighter, sexier. The whole package. Of course, I had to try them.
My favorite tube and the reference 6SN7 in my system is the Sylvania 6SN7GTA short bottle chrome top from the 50s. The Syl. has great detail, wonderful air, the high end is sparkly and yet refined without any harshness. The bass is tight and low and strong. It keeps things quick, but I personally think the rectifier tube affects the speed of an amp more than the driver. The Syl. images wonderfully and the image is tight and solid and holographic. I figured I would plug in the CV181 and get all of these qualities only MORE SO. Like it would be a Syl. GTA just with more gain. More power. More authority.
I was wrong. Immediately, the CV181 was underwhelming at best. The only thing about it that met my expectations was the higher gain. It is a higher gain tube than what I was using (for some reason). The high end went all muted and cut off. The high end detail in particular suffered significantly. The resolution in general also decreased significantly. The bass was out of control. It lost all tightness and became wooly and one-note-ish. The soundstage flattened out and lost cohesion... It wasn't harsh. It was almost the opposite of harsh. Not brittle. So it has that going for it. I've heard brittle sounding Chinese tubes and I always thought that was the signature of Sino tubes. These break that mold.
I dare say that my Sylvania GTBs from the 50's (taller, chrome top, yellow labels) sound better. And the GTAs sound significantly better than the GTBs.
Now, this is not a review as much as it is a long question. If the CV181 has the EXACT OPPOSITE effect in my system than it does in a lot of other systems, and if my favorite is the GTA, what kinds of additional 6SN7s should I be looking for? BTW: the GTA sounds better than my Ken Rad dark glass and VT-231s by Sylvania and Tung-Sol something or others I have lying around. Should I just look for more of the same? Is there better? Also, I'm curious, has anyone else had similar results to mine?
Here is my system: Sylvania big bottle 5AR4 rectifiers, choked power supply, 6SN7 driving 300B SET, Cain and Cain back-loaded horns with a single fostex full range driver and super tweeters. All cables are 47 Labs OTA single strand copper. I tested soundstage and imaging using speakers because I don't consider imaging as much of an issue with HP. The ultimate soundstage compliment I can give a supra-aural headphone (or any headphone for that matter) is if they sound like they disappear. In my opinion this is as good as imaging can get with a headphone. Speakers image as if the musicians are right in the room, sitting in front of you. HP can't really do that.
Any comments or advice or invitations to tube rolling parties would be welcome."