New Production 12AX7/ECC83/7025 Vacuum Tubes

[tbonesullivan]

So yeah, things aren't like they used to be. Only three factories remain, however all three have been working with various companies to improve the quality of their output. Tube Amp Doctor has been working mainly with the Shuguang factory to produce improved preamp and power tubes.  Also New Sensor and the Saratov Xo-Pul factory have been putting out lots of "reissues" under the Mullard, Tung-Sol, etc.  There are also the usual tube dealers such as Groove Tubes, Ruby, Penta Labs, and now the "Preferred Series" from The Tube Store.

What I have found, is that in many cases, the Tube Amp Doctor tubes are the same tubes as the "Preferred Series" from the Tube Store. Ruby also often will have these same tubes, under different names, so it can get confusing as heck. Mesa Boogie also gets tubes from these same factories, so aside from their testing, they are the same tubes.

Now, I now that old glass is preferred by most people, but the cost, time, effort, etc involved is in and of itself something to worry about. Also there are plenty of audiophiles with deep pockets willling to spend $500 for NOS Telefunken preamp tubes.

Anyway, some of my current favorite preamp tubes:

Sovtek 12AX7LPS - Long Plates, Spiral Filaments. Nice tone, and my Phase Inverter of choice. Long plates makes it kinda bad for gain stages in combo amps, and even in a head I would think about whether you want your V1 to have long plates. Not suitable for Cathode Follower spots

Electro Harmonix 12AX7 - Short Plates with Spiral Filaments. Just a good all around tube. Not suitable for Cathode Follower spots.

Tung Sol and Mullard Reissues - These are also good tubes, with slight variations in design, all coming out of the Russian factory under New Sensor guidance. These also have spiral filaments, so like the others, they also won't work with Cathode follower spots.

Chinese "Silver Special" 12AX7: These are 9th gen chinese that have unplated  plates. They get a very nice overdrive. They may be discontinued though.

JJ ECC83S - While these aren't the most harmonically rich tubes, they are low noise and very durable. At present all of Mesa Boogie's preamp tubes are this tube. They work in Cathode follower spots as well, and are fairly high gain. They are kinda dark sounding though, so I would not recommend putting them in EVERY slot.

Chinese "Mullard" Style. These are marketed as the Ruby 12AX7AC7, Preferred series 7025, TAD 7025-S. They have "mullard style" plates, and are warmer to my ears than the standard Shuguang 9th Gen tubes.

Chinese/Shuguang 9th Generation tubes: If you get an amp and it's got 12AX7A China written on it, that's what this is. They are also marketed by just about every tube dealer. They are warm, and have a nice overdrive sound, very popular with marshall fans. Cheap, consistent, and also good for cathode followers.

So, that's what I've been using for the most part now, with the exception of some used tubes I have.

Also, regarding the "Cathode follower" issue, many amplifier designs put in Cathode follower circuits that are actually way over spec for the Cathode to filament voltage. The old stock tubes with the plain filaments could bear it, and so can the new production tubes. However, the Russian plant started using a spiral filament design, and unfortunately this design cannot handle the over specification voltage, and they stop working. Pretty much Every Marshall amplifier uses a cathode follower directly after the tone stack, before the phase inverter, and they are used in many other designs as well.

 

[jwhitcomb3]

More vacuum tubes? in 2019? It's like Night of the Living Dead!

[DeVai]

Thank You

[RobB]

38 minutes ago, tbonesullivan said:

Also there are plenty of audiophiles with deep pockets willling to spend $500 for NOS Telefunken preamp tubes.

A fool and their money are soon parted. 

[Dave Scepter]

Good info, thanks for sharing 

[tbonesullivan]

I'd do one on power tubes, but honestly I don't drive my amps hard enough to really know, and rolling preamp tubes is a TON easier than power tubes. No biasing/etc involved.

One thing I can say is that you should always do your research before buying. I've had good luck with Doug's Tubes, The Tube Store, Tube Depot,, and Antique Electronic/Tubes and More with my preamp tubes. They overlap quite a bit in what they carry, but prices are different, and some offer services that others do not.

I don't really have much feelings either way on the "high Gain" or "balanced triode" thing. Testing for microphonics is definitely good though, and as with everything, you need to consider where the tube is going, and what function it will be playing. For example, some amplifiers have all AC filament heaters on their preamp tubes, while others have DC, usually on the first few tubes. Having a spiral filament tube in your V1 slot on amps with AC heaters can reduce background noise and hum, because the hum would cancel out.

[Dave Scepter]

Sir, your vast knowledge on vacuum tubes is quite impressive... And I for one appreciate your input... Feel free to share more of your tube knowledge... as a matter of fact, you should start/ post a vacuum tube 101 class... I'm always open to learning something new or refreshing past knowledge 

[Jakeboy]

I much prefer old glass...especially “pulls” ...ie...used USA/Euro tubes that still test great. I find them everywhere. They work for me and are extremely durable.

I did just buy a brand new Ruby 12ax7-c5 high gain for my Blonde Bassman Normal channel and it works quite well. Have had luck with JJs too.

[Dave Scepter]

59 minutes ago, Jakeboy said:

I much prefer old glass...especially “pulls” ...ie...used USA/Euro tubes that still test great. I find them everywhere. They work for me and are extremely durable.

I do the same as well however, it's getting increasingly difficult to find pulls nowadays... as well as older alnico speaker pulls

[tbonesullivan]

Pulls will last a while, but not forever, and getting the right pulls is time consuming. I've got a bunch. Heck I've even got a spreadsheet showing what's in each of my amps, which is another good suggestions to help keep track of what you've got where. There are some good sellers on ebay and reverb if you want those, but supplies are always a problem. Also, figuring out exactly what something is can be hard as well. One of my used pulls says RCA, but it's really made by Tungsram in Hungary. Still a great tube, but not really an RCA. I've got another marked motorola that I have no idea what it is, and one I think is an RCA 7025.

With the new production tubes, that's not a problem, for now at least. Sadly it was not enough to convince Svetlana Electronic Devices to keep their old St Petersburg Tube production facility open. They were producing great tubes, which people said were the closest to the old production levels.

[Dutchman]

I’m lucky to have collected tubes for amps for decades so I have not used any of the new tubes. I’m somewhat suprised that they wouldn’t be better today with the new state of the art equipment that’s avaiable. The designs are already there. I know tubes ruled the world so competition was tougher back in the day. Why can’t we do as good as we did 50 years ago??? With amps, guitars, tubes, it just doesn’t make sense???

[tbonesullivan]

2 hours ago, Dutchman said:

I’m lucky to have collected tubes for amps for decades so I have not used any of the new tubes. I’m somewhat suprised that they wouldn’t be better today with the new state of the art equipment that’s avaiable. The designs are already there. I know tubes ruled the world so competition was tougher back in the day. Why can’t we do as good as we did 50 years ago??? With amps, guitars, tubes, it just doesn’t make sense???

From what I gather, a lot has to do with the starting materials, particularly the plating on the internals, and just the fact that production is no where near what it was back in the day. A lot of skill and techniques were also lost as the factories in the US, UK, Europe, Etc closed.  The JJ factory in the Slovak Republic was only started in the 90s, from the leftovers of the TESLA factory, which had closed about a decade before. The Shuguang Factory in China is also not that old either, and the Chinese tubes that all the major makers were using in the 80s were from the long-closed Beijing tube factory. The machinery/etc was moved, and they use the same designs, but every move loses something.

[BoogieMKIIA]

Having worked in the CRT and cathode industry, my opinion of what is important for a good vacuum tube.

 

1. Materials.  The cathode chemistry is key and any material the oxide cathode compound is in contact with. This goes to electron emission and life. Coupled with the correct heater design and placement, you get optimum work function (lower is easier to pull electrons from the cathode) and lower evaporation of the cathode compounds (life). As far as sound/tone, likely only noticeable when things are bad or on the edge, other than shorter life.
2. Cleanliness. All aspects. Preparation and handling of the parts and the vacuum pumping system. Any chemicals not needed, any residual gas can poison the cathode resulting in low emission (strength, life). Can also cause unwanted emission between parts, arcing.  Pumping the vacuum requires heat (~400C) and time, along with a clean pumping system. Would be easy to skimp here. Indirect RF heating can be added to drive residual gas from the steel parts. High vacuum is weird - you get to molecular flow, which means probability over time that molecules make it out. That type of pump is either an oil diffusion pump or turbo molecular pump.
3. Accuracy and durability of construction. You would catch accuracy issues by testing for the most part.  When things move, the characteristics can change at best, failures at worst.

I don’t know enough about the design details like long or short plates to make any comments with regards to differences is sound.  From a test and characterization perspective, a 12AX7 is a 12AX7. Easy to understand that things like microphonics can relate to the mechanical differences.

I don’t think it is impossible to make high quality tubes today. Maybe the top issue would be securing consistent and high quality cathode materials and heaters. Those items are not produced in such large quantities and by multiple suppliers these days. Someone has to understand the important details of those exotic compounds.

 

 

[Jakeboy]

Tbs, why do you avoid long plates in V1 in heads?

Combos I have always been told are hard on long plates in V1 due to vibrations in the combo amp from the speaker. That problem doesn’t exist in a head, at least not to the same degree.

I have successfully used long plates in V1...why don’t you like them in gain spots?

[tbonesullivan]

7 minutes ago, Jakeboy said:

Tbs, why do you avoid long plates in V1 in heads?

Combos I have always been told are hard on long plates in V1 due to vibrations in the combo amp from the speaker. That problem doesn’t exist in a head, at least not to the same degree.

I have successfully used long plates in V1...why don’t you like them in gain spots?

 The long plates are simply more prone to microphonics, and especially in high gain amplifiers, V1 should be the most vibration resistant tube. It's more of a play by ear thing.  Also in general there really aren't many "long plate" designs among the new production tubes.  I haven't had problems myself, but other people have had them. That said I have had no problems with Long Plate tubes in any position in the heads I own, though I don't play them at stage volume. At "normal" volumes I don't see how they would be an issue at all.

This is the reason why when you get a new amplifier from most makers, it's full of tubes like the Sovtek 12AX7WA / GT12AX7-R or the Sovtek 12AX7WB. They are not the best sounding tubes, but they are very resilient and have great microphonic resistance. So, they survive shipping, and don't howl.  Mesa Boogie relabeled the 12AX7WA as the "Russian" 12AX7 , and now they use all JJ ECC83S tubes for the same reason: they don't want problems. With super high gain amps everything is amplified and compressed to such a high degree.

[tbonesullivan]

28 minutes ago, BoogieMKIIA said:

1. Materials.  The cathode chemistry is key and any material the oxide cathode compound is in contact with. This goes to electron emission and life. Coupled with the correct heater design and placement, you get optimum work function (lower is easier to pull electrons from the cathode) and lower evaporation of the cathode compounds (life). As far as sound/tone, likely only noticeable when things are bad or on the edge, other than shorter life.

I don’t think it is impossible to make high quality tubes today. Maybe the top issue would be securing consistent and high quality cathode materials and heaters. Those items are not produced in such large quantities and by multiple suppliers these days. Someone has to understand the important details of those exotic compounds.

I have heard that the Chinese "Mullard Style" tubes marketed by Tube Amp Doctor, The Tube Store, and Ruby tubes, use plate material that is manufactured in Germany and them sent to the factory. They also use triple mica spacers.  On the other hand, I've seen some designs from TAD and Ruby from the Shuguang factory that have unplated anode plates, the Silver Special, and also the new ECC83WA from TAD.

[BoogieMKIIA]

The black color is from wet hydrogen firing.  One purpose is to suppress stray emissions but audio vacuum tube voltages are not that high compared to picture tubes.  High temperature can also contribute, from the heater. The German material could very well be cleaner by virtue of good process control.  Also means the plates were already formed before firing, possibly greater accuracy of dimensions from that operation in Germany.

There could be other reasons for the black plates but I built lots of projection CRT electron guns with plain grids that operated at 36KV and did not have emission issues. 

[black magic]

I have tried a bunch of pre-amp tubes and I play high gain and loud. They all sound different, but the only tubes I ever hated were JJ pre-amp tubes. They are very dark and dull sounding-yuck!! I like a high gain Tung Sol in V1 and EH the rest of the way including the power tubes. I use to like the EH 6CA7 power tubes, but they went to poo. Don`t know what happened there?

[tbonesullivan]

Did they just blow, or can you not find them anymore?  I will say that a lot of people are not big fans of JJ tubes in general. The guys are Eurotubes are huge JJ fans, and Mesa Boogie is too (right now anyway) but I never found that the "all JJ" sound was to my liking.  Of course, it also depends on what you are equipping them on.  I remember hearing a comparison sound test probably a decade ago using RFT, JJ, Groove Tubes Mullard copy, Bugle Boy (Amperex) and a real Mullard.  There were differences, but not HUGE ones. The JJ was kinda harsh at low gain, but sounded good at higher gain levels. They were using a Tophat amplifier.

I just looked around, and there are some pretty nifty shootouts between the current production. What's always interesting is to see how the different retailers look at the same tubes.

https://www.amplifiedparts.com/tech-corner/12ax7-comparison-current-made-tubes

https://www.thetubestore.com/12ax7-tube-reviews

[tbonesullivan]

Also, there are actually more than just the three big producers of vacuum tubes, but the smaller "boutique" makers specialize in tubes for the Hi-Fi and specialty use market. A lot that i looked at don't even make standard preamp or power tubes.

https://theartofsound.net/forum/showthread.php?44432-State-of-the-Vacuum-Tube-Industry-2016