12au7 tube?

No I do not ever try to match brands of tubes together nor have I ever thought about that neither do I see any benefit to it. Almost all of my equipment is operating with all different brands of tubes. Even though I had Mullard MCI 12ax7’s as input tubes, my favorite 12ax7 is the Amperex long plate double DD getter. But at the time of evaluating the EL34’s, I had the Mullards in the input. The Mullard MCI btw are some of the best 12ax7’s ever made.  In the beginning, Depending on the type of tube equipment I’d own in the past, I usually was very curious at how much improvement in sound I could get by picking up premium tubes that were favorites by many audiophiles that were in the hobby before me. Slowly I began purchasing tubes and listening to them in my amplifiers to hear what they sounded like and to satisfy my curiosity. Nowadays when I’m in need of a specific or special sound I’m hoping to achieve, I have some of my favorite tubes to put in place and see if it helps. Ive been in this hobby for 30 plus years and I already know by listening to a system if it’s good or if it’s lacking. I only swap tubes today if I hear a problem. If it sounds good, I change nothing. My ears tell me when something is transparent, revealing, airy, engaging, natural, and all the beautiful things we want to hear from our systems. If I purchase a new piece of equipment that has Chinese tubes, I very much might keep those tubes in as long as it sounds transparent and good. When I purchased my Conrad Johnson Premier Four, it arrived with 8 Shuguang Chinese EL34’s. First thing I wanted to do was get them out and put something better. But after playing the amp for the first week, I found no issue with the Chinese tubes. To my ears, they sounded great and were doing the trick. So instead of putting in 8 Teslas, I searched for more Shuguang tubes and purchased 16 as backups because in the end, it just sounded fine. I did change out the input and driver tubes on the amp to something better from my vintage stash. I feel setting up a system is a mix of a lot of different stuff. I don’t recommend using the same brand of tubes the same way I wouldn’t recommend using the same brand of cables throughout a system. Building a really nice sounding system is something that is done one step at a time and to get it to be really, really good, it usually takes time tweaking and making little but worthwhile adjustments. It can take yrs till it all finally comes together and the funny thing about this hobby is that when that happens, usually audiophiles still aren’t happy.  I do t think many audiophiles will ever be content or happy with their systems. 

Well, most audiophiles are hard to please and always strive for even better sound than they might already have.

I see, no real reason to think that one tube brand everywhere would have an advantage.

With cables, I think it might depend, though I don't have enough experience to be sure.

I mix match cables and try to use quality cabling. I pretty much don’t use basic cables. I had them in the past, Wireworld, Audio Quest, Cardas, MIT, Tara Labs and so on. I’ve been using newer cables from new companies that sound better to me than cables of the past. I have a limit to what I want to spend on a cable and keep it at that. Today some really nice sounding IC cables can be purchased from $100-$500 pair. Speaker cables as well. Yrs ago not so, for that price only decent sounding but today things have changed and some really good open sounding cables can be purchased at a reason price because we have so much new on the market. I like using silver a lot on my IC’s. I find silver more open, smoother and natural over copper. Thank God I’ve found contentment when I get a setup sounding good. I usually leave it alone and enjoy the music and that’s really what this hobby should be about. But I went through a lot of listening to components, tubes, cables to satisfy my curiosity. 

If you can find a pair of these, grab them. Westinghouse carbon plate 12au7, but a very specific limited production type.

So why this tube is not very well known? It’s very hard to find and even if you find it you have to be careful what you buy. The tube was produced by Westinghouse for a short period of time and after that was sub-licensed from RCA, which didn’t produce the same sound.

Here are the signs of the original WH 12au7:
1) Dots around 12au7 – not the GE type dots, but smaller dot’s in grayish color.
2) Getter must be raised on a copper post above the plate (RCA has them always attached to the plate). For of the getter is Large D with TWO (2) wires attached at the end (RCA only uses one)
3) Silver cover above getter is very extensive (RCA’s is much smaller). This makes it really hard to see the getter. I mean super hard – if you can see it easily, it’s not the real Westinghouse.
4) Plates are not shiny black like RCA, but carbon black. Very unique color – it’s not similar even to Ken-Rad of the same period. It’s like charcoal – a mixture of black and very dark gray. This makes it very hard to distinguish them on pictures – because the color depends on lighting.
5) Yellow color letters with number 337 for the manufacturer – if you are lucky to get silk screen in good shape.

I have a couple 12au7 type preamps. For nice clarity & sound or a step above the usual suspects of 12au7’s I think the Siemans with silver plates are a great tube. I also always seem to like anything Holland Amperex. I find that the much cheaper early GE tubes to be close in sound to the balanced characteristics of Amperex tubes. Valvo’s are always a winner as well.

If your transformer can handle it I really prefer the E80cc tube. They have a 10,000 hour life span so you definitely get your money’s worth. Great clarity & dynamics. The Tungsram are a fine tube. I recently bought some PCB’s from Mellow Tone Kits & just copied their e80cc schematic & it was a good preamp with lots of drive & low output impedance I paired with a Hypex Nilai.

I’ve also tried the e80cc with adapters in my 12sn7 & 6sn7 preamp circuits. I preferred them with 12v on the heater but will work with 6.

The American 5814 tubes are good 12au7 types as well for the money I feel. 12bh7’s even better if the transformer will allow.

For 6sn7’s the early 50’s Sylvania chrome dome gta’s are a safe bet. Some pretty good 6sn7’s that don’t have a crazy price tag are the early 50’s GE GTA’s. Side getter, copper grid posts, parallel gray plates, short bottle. I just picked up another nice pair recently for about $50. GE’s don’t get much love as any tube type..but they have some gems that can be found cheap due to this No Love. They are great as cathode followers. A lot of the VT-231 type tubes are just stupid expensive in my opinion. I don’t notice a big enough difference in good 6sn7 tubes to justify the cost.

I am a fan of the 5692 tubes when plate voltages are under 200volts. These are expensive but in the right circuit are very quiet, transparent, dynamic, enlarged soundstage, just smooth & sweet. 10,000 hour life to maybe justify some costs. In the wrong circuit (high voltage) they can sound grainy & lifeless..& burn out quick. I also like most early RCA 6sn7 types in general. Smoked glass being less transparent but fun for certain genres. 

6cg7 types with 8 to 9 pin adapter go nicely in any 6sn7 spot. These are identical to 6sn7’s in 9 pin form.

I prefer 12volt 12sn7’s..though they are supposedly identical to their 6 volt brother/sister.

I’m currently using a pair of Sylvania JAN CHS 6sn7wgt in my Icon Audio LA4 preamp & liking it. I’ve used other wgt’s in the past & didn’t totally love them. This pair that I really like actually took me awhile to put together a matching pair..buying one & finding a match many months later. Compared to my other wgt’s these have the bottom round plate slightly above the base, a half chrome top but can see the 4 hanging filaments. Mid 50’s, 3 hole, shorter bottle but without super short plates..white lettering.

Buying singles can lessen the cost but can sometimes take awhile finding a good balanced match.

But I think it really comes down to the circuit if the tubes sound well. And almost all tubes should sound good to decent in the circuit. Usually if NOS tubes don’t sound good it’s probably because something is wrong with one of the tubes. If the tubes are good the music should sound good..some tubes just sound slightly better than others. Everything in this post is just my opinion of course.

With quality tubes being so scarce & ultra expensive I should really start trying more aftermarket/new tubes to see what works well. I have no experience with newer tubes.