LTA MicroZOTL tube upgrade


Hi everyone,


I’m thinking about changing the default tubes in my gear and was wondering if anyone has experience with replacing the stock 12AT7s with Ray Select 12AT7 or any other tubes that add some warmth and density to the sound.

gabriel123

@tyray 

I bought as much of the American market (and UK market for that matter) of A2900s that I could a couple of years ago, kind of accidentally cornered the market in a way as I had well over 100 of them at one point, which included a code-matched octet. At the time I was running 20 of them in my kit, 16 in the signal path at any given time. When you’re ready to pull the trigger on some let me know and I can help you vet what is a truly great pair and what is not. There are a lot of wildly off balance/mismatched pairs of GEC A2900s out there that will have no problem taking your money. That said, I had bonkers off balance pair I would use as a demo pair for my clients, which I would tell them in advance of sending them the pair, but not one person could detect the difference in listening to them.

Here’s a somewhat informative write up I once had included on some of my listing pages that details their sonics and technical details. 

Enjoy,

----------

Hearing is believing.
 
You’re thinking it’s expensive. Too expensive. There’s no way it could be that good, that much better than all the other 12AT7 or 12AX7 tubes out there. Only an idiot, moron or your brother-in-law would pay a guy (who can’t even park straight) that kind of money for what, a used tube with a peeling sticker? Well, you’re right about a couple things. It is expensive, but remember, grasshopper, that price and value are different things. Ask anyone that’s bought one if it was too expensive, I betcha not a single one will say so. The only people that talk about it being too expensive are the all tubes are the same skeptics, a group largely comprised of degenerate forum fiends who’s only real contribution to society is ensuring whoever the poor soul is that mops the mouth foam off the floor of the echo chamber gets enough over time. You’re also right that it’s not the best 12AT7 out there because the A2900 is no more a 12AT7 than it is a banana. For all that the A2900 does so brilliantly, it fails us all as a banana.
 
The A2900 is what Mr. Royal my 7th grade science teacher would call an abundant enigma. He also called me an abundant enigma, but a story for another time. Not 12AT7, not 12AU7, not 12AX7, the A2900 goes its own way. Built like a tank because it was built for a tank, the A2900 was meant to be used during wartime, not the joystick wars we fight today, but getting hard shelled with your pants down by a Panzer twice a day kind of war. It’s highly probable someone has submitted to the business end of an A2900 in hand to hand combat. When it’s not giving your 12AT7s a wedgie, the A2900 can be found bragging about its 10,000 hour life expectancy, its ability to dissipate 3.5w of plate current vs. the 12AT7s 2.5w, and that it can take 550v of straight lightning with no chaser compared to the those 12AT7 lime lickers than can only take 300v of canned heat. The A2900 can be best defined by what it is not: colored, syrupy, overhyped, or exaggerated. This is the most natural and neutral sounding 12AT7 variant I have heard. It fully communicates all appropriate musical emotions intended by the artists without adding any embellishment of its own. This almost seems like I’m damning the tube with faint praise, but I must be clear: the GEC A2900 adds nothing and removes nothing from the sound. It facilitates a true connection between the listener and the music. This tube gets out of the way and lets the music happen in a manner unlike any other.
 
How do they sound? It’s the only tube other than some of the finest Siemens tubes that I have heard that can balance being absolutely transparent with being pleasant to actually listen to. One true flex of the A2900 is its almost comically large soundstage relative to other tubes; going back to those other tubes after the A2900 feels like you’re watching a concert take place in an airplane bathroom. Natural mid-range, fantastic controlled bass, a musicality that doesn’t add any color whatsoever. This tube has performed excellently in both 12AT7 and 12AX7 sockets. I’ve even pressed it into service as a 6SN7 substitute (using the appropriate socket adaptor) with superb results. In my experience, the A2900 tube will perform anywhere it is applied. It’s not a 12AT7 or a 12AX7 or a 6SN7 or anything else. It is an entirely unique creation that will lend its special quality to any system where it is installed. The Brits designed this tube with purpose, and it is immediately audible. The A2900 is highly capable, incredibly tolerant, and sonically impressive. In fact, I recommend the A2900 be used in almost any  amplifier design specifying a standard 12V dual triode. I cannot be effusive enough in my praise for this tube and its quality. Top shelf, indeed.
 
You know what is expensive? Parking tickets. 
 


 

@troutstreamnm 

 

RE: Brimar vs. Mullard, it really depends on the exact tube types you are comparing. Both generally have the warm British sound.

As I've mentioned the triple mica black plate Brimar are wonderful tubes.

Many like the Mullard M8162. 

You can find some great Mullard 2-Mica CV4024 for about $25-30 each if you're diligent. Great tubes for the money. Later production (early 80's) is what you're most likely going to bump into as NOS tubes, but again, great value.

If you want something more geeky, rarer, altogether better, look for late 1950's Mullard Whyteleafe CV4024. Most folks are familiar with the Mullard Mitcham and Blackburn plants, but they had another one at Whyteleafe that just made superb tubes. Their factory symbol is a square with a line drawn diagonally through it. The 12AT7 produced there are exceptional. All of the normal characteristics of Mullards, beautiful mid-range, silky smooth highs, but also vey tight, disciplined control of the bass which is particularly unusual for Mullard tubes. The Mullard 10M 12AT7 is another nice one. I have some Mullard E81CC/6201 but they honestly haven't done too much for me. Valvo E81CC are better. Siemens, too.

Another delightful rarity are the early 1950s Philips Copenhagen 12AT7/CV455, etc. Very rare. But exceptional quality. These are often misidentified as Philips Herleen tubes because both plants use a triangle as their mark, but the triangles are different. If you pay attention to that you can scoop up some EXTREMELY valuable Philips Copenhagen Welded Plate 12AU7/12AX7 for a $100 or so when they are worth $1K+ because someone thought they were Amperex tubes.

If you wanna get geeky with your 12AT7, look into 7062 and E180CC. There are some very nice pinched waist examples of both out there.

Good hunting.

 

@tyray 

When you say GEC Version 1, what are you referring to? The tubes in the post that was linked are later 1970's 2-Mica production. If you see the four digit codes on the tubes like those the first two digits are the year of manufacture. Still nice tubes. 

But if you want to go after it, I recommend chasing some of the earlier production 3-mica tubes. Don't pay a premium for the CV-6091, I don't think there is any difference whatsoever. Not in my experience anyway.

@chickenoregg

I do have a source, in fact she explained the GEC A2900 tube to me this way. 

 

Thank you for your question regarding the GEC A2900 ECC81 / 12AT7.

The production code you referenced, 7838Z, indicates that these tubes were manufactured in 1978 (week 38). Based on this code, these are later-production GEC A2900s, not the early or “Version 1” examples from the 1950s–early 1960s.

That said, they are still genuine UK-made GEC A2900 tubes and represent very high-quality NOS production. Later GEC A2900s are known for excellent consistency, strong electrical stability, and very low noise, which makes them especially well suited for recording, phase inverter, and hi-fi applications.

While early A2900s are often sought after for their vintage character, many users actually prefer these later versions for their cleaner, quieter performance and reliability.

If you have any questions about how this tube might perform in your specific application, feel free to let us know and we’d be happy to help.

Best regards,

And these are NOS / NIB with seafoam blue lettering and lite cream background. But I would love to buy a couple off of you when funds and time permits and hopefully I can get some NOS / NIB with seafoam blue lettering and lite cream background or whatever you suggest at the time.

Funny, no one has ever brought this tube to my attention so I've never even heard of this tube before.Thanks, appreciate your help. I'll be in touch.

 

 

 

@tyray 

I think what she wrote is fairly accurate. The later generation 2-mica tubes have a very nice consistent tone. One of the biggest differences I have noticed is that they are much more balanced. Some of the early tubes are Charlie Sheen level off-balance. I have had a few pairs lately of NIB later production 2-mica A2900s and they have been great, I keep selling them though before I really get much time with them, Such is the life of a Tubesman. Keep in mind that GEC tubes can take quite some time to full burn in and mature to full bloom. Upwards of a year for the older tubes. They always sound great, but the older, almost used up ones are the best. I find this true of most tubes, I love listening to a tube that’s fully seasoned and peaking out. 

Keep in mind the A2900 is not a 12AT7. You can also sub it for a 12AX7. Gain wise, its smack dab in the middle of 12AT7 and 12AX7 (same as 5751). I had a pair of mono-blocked MC275s that called for four 12at7 and 3 12ax7 each, used 7 A2900s in each to glorious effect.

Here’s a link to a guy named Tom on Head-Fi. While I would be happy to help you, Tom’s prices cannot be beat if he still has tubes left. I cannot remember his story, but at some point, long, long ago, he came into a veritable grip of A2900s and meters them a pair or quad at time to those he feels deserve them. I think they are 360 euro for a NIB matched (possibly code matched pair). I have bought from Tom and can vouch 100% for him. He’s a stand up guy.

https://www.head-fi.org/classifieds/gec-a2900-ecc801s-e81cc-ecc81-12at7.10203/

Enjoy the roll.