The hidden gem among 12AX7/ECC83 NOS tubes, the RFT ECC83

[Miles_ONeal]

Since many of us use tube amps or preamps, and like to do at least some tube rolling, I decided to post this here.


It is about a less known vintage tube(s) made by a company called RFT. These tubes were made from the beginning of the 60's till the end of the 70's in the ex Telefunken plant in Erfurt, that remained in the Soviet occupation zone. Presumably, some of the Telefunken tooling from the 40's was used and modified to make these tubes. They mostly made small tubes for radio and audio applications. Although, their EL34s are very highly regarded, I'll focus on their ECC83/12AX7 tube.


I call the RFT ECC83 the hidden gem among all NOS tubes. They used to be widely available in Europe, especially Germany and Eastern Europe until about 10 years ago when the stocks started to slowly dry out. They were dirt cheap, costing considerably less than new production tubes. Prices have gone up since then. The last couple of brand new tubes costed me close to $25 a pop including shipping. IMO, even at that price they are a steal. The tube is very short plate, which helps with microphonics.The gain is typical of 12 AX7/ECC83 tube, possibly slightly less than the hottest of the LPS.


RFT ECC83/12AX7 sound nothing like any new production tube. I'm not that kind of guy that will take about a night and day difference in instrument amps when changing a single tube, but this one definitely have a character on its own. It's warm and thick sounding, you'll immediately notice it. Put it in V1 position and you'll hear your amp getting thicker. The bass is rounded and the mids are thick and prominent. I know that some guitarists love this tube in newer Marshalls where it offsets the brightness of these amps. It is bass amps/preamps that the RFT ECC83 shines, IMO. I've used them in all my tube gear for close to 15 years now (3 amps and a preamp/DI box). It made all my tube gear sing. Again, I'm not a big tube rolling guy, and wouldn't spend a fortune on NOS tubes. I don't find much sound difference in most new production tubes I've tried,and even some old ones, but these ones are different. Lately, I put one in the V1 position of my newly acquired Ampeg PF20T. Immediately noticed the warm character. It brought this little head a step closer to a real B15.


Just a piece of advice. Ifyou find some of them at a decent price, do not hesitate.

I only had one of these when I was building/modding/repairing guitar amps and it was awesome. I bet it's kickass for bass.

 

[Deleted member 271037]

Based on what I've read here, I think I want one for the OD channel on my Verellen Meatsmoke. I already keep the treble rolled down all the way on that amp and still find it on the bright side.

You might also consider the early 60s version of the GE long/grey plate 12AX7. These tubes roll off the highs a bit, without the loss of clarity or the early breakup you get with the RFT. Because of the slightly subdued highs these early 60s GE long plates aren't very popular with guitar players or with the hi-fi crowd, which means the prices haven't gone totally insane (or at least not quite as insane as with many other NOS tubes...). These GEs are SUPERB in bass amps.

Just to be clear: I'm NOT talking about the slightly different looking and quite different sounding late 50s GE long/grey plate 12AX7. These do not have the slightly softened highs of the early 60s version. And I'm DEFINITELY not talking about the later (mid 60s and onwards) GE short plate 12AX7 (very rugged but not nearly as nice sounding as most other NOS tubes).

Then again, for an OD channel, maybe the RFT could be fun!

On the cheap, if you simply want to mellow out a bright sounding amp: The JJ ECC83S will definitely do this. But it will come at the cost of low extension and clarity. Even more so than with the RFT, and without the unique overdriven RFT tone. This particular JJ is one of my least favorite tubes, except MAYBE for taming an overly bright amp. It will certainly do that.

Of course, not all amps with tubes in them respons the same to tube changes. In my experience, modern hybrid amps and channels switching amps don't respond nearly as much to tube changes as "old school" all-tube amps. I have never tested the Meatsmoke, but it looks like a type of amp where I guess the tubes could make a difference.

 

[blr2]

I don't seem to experience any lack of clarity with the RFT ECC83 in V1 position of my Ampeg PF20T. On the contrary, Plugged into an Ampeg 210AV I get much, much better clarity compared to a Rumble 40. I know, apples to oranges, but still... Also, no clarity loss compared to the stock Ruby tube. Warmer, fatter-yes, but not muddy.

 

[Deleted member 271037]

I don't seem to experience any lack of clarity with the RFT ECC83 in V1 position of my Ampeg PF20T. On the contrary, Plugged into an Ampeg 210AV I get much, much better clarity compared to a Rumble 40. I know, apples to oranges, but still... Also, no clarity loss compared to the stock Ruby tube. Warmer, fatter-yes, but not muddy.

This will of course depend on what you're comparing the RFT with. Ruby can mean lots of things. They have never actually manufactured any tubes themselves, but they have rebranded lots of different tubes over the years. It might have even been a JJ ECC83S, which in my opinion suffers VERY badly from a lack of clarity in most amps, but without the cool stuff you get with the RFT. The JJ is just muddier sounding than most other tubes IMO. With the RFT it's more a matter of the mids sounding kinda "congested", which can actually be very cool in SOME amps, but for me the RFT has been very hit-or-miss.

Ampeg vs Rumble isn't really relevant at all in this context.

In a direct comparison, in the same amp, the RFT definitely has less detail/clarity, earlier breakup (less clean headroom) and rolled-off highs compared to other vintage tubes. But if you like the character of the RFT you should definitely stick with it. There's nothing quite like it.

 

[blr2]

The stock tube is Ruby 12AX7WBC HG+. AFAIK it's Chinese tube, definitely not rebranded JJ ECC83S, since it looks different inside.
The difference in tone between these two tubes is not big. We are not talking night and day here. It's audible at low to moderate volumes, but I doubt it could be heard in a mix. Since I'll be using the PF20T for home practice and recording (low volume), the early breakup of the RFT is not much of a concern. In fact, I wasn't able to make it distort until levels far exceeding my home levels.
I'd agree that most of the difference the RFT makes is in the midrange. It has thicker lower mids, and just a bit less treble that could be easily compensated at the treble control. Again, not a big difference. It's not like changing pickups or even strings, just gives the amp just a bit different character. As I pointed above, I'm not a big believer in tubes making huge tonal difference, especially in bass amps,and I would never pay three digit sums for NOS tubes. For 25 bucks, however, I'd recommend this to anyone who wants to experiment a bit with tube rolling. Depending on the circuit and position it may or may not make any difference. In fact, the PF20T (V1 position) is the one piece of gear, in which, it makes the most difference. In my other tube equipment, not much at all.

 

[Chuck M]

I was heavy into using bass preamps with at least one tube and a power amp. I tend to go overboard when I am interested in something so I have tried a lot of tubes.

Fisher branded tubes are West German Telefunken tubes easily identified by the diamond molded into the glass in the middle of the pins. Telefunken made two popular versions of the ECC83/12AX7A. They made ribbed plate and smooth plate versions. Both were long plate tubes and the smooth plate version was coveted by hi-fi enthusiasts who used tube equipment. I found the smooth plate version to be a wonderful sounding tube in bass preamps. It has great clarity in all frequencies, is very low noise and the highs are very detailed with no harshness.

The tooling for these tubes was used for a time in Eastern Europe. I don't recall which country they were used in. For a while they were available in the US with Groove Tubes markings. They were nice tubes but the Telefunken tubes sounded better to me.

Tube companies frequently bought tubes from other manufacturers and rebranded them. A genuine West German Telefunken tube will always have the diamond mark mentioned above.

Tube choice is personal. If possible, try several different tubes and use what sounds best to you.

The Telefunken smooth plate is my favorite but I have also enjoyed Sylvania and RCA long plate 12AX7A/7025.

 

[LiptonJigglers]

Perfect timing.
Im on the hunt for a new tube today..
Thanks for the report.

 

[blr2]

I found the smooth plate version to be a wonderful sounding tube in bass preamps. It has great clarity in all frequencies, is very low noise and the highs are very detailed with no harshness.

I have no doubt that the Telefunkens are among the best 12 AX7/ECC83 tubes ever made, but at $200 a piece, I'd much rather spend the cash on something else. The prices of NOS tubes have gone crazy for the past 10 years. I paid $450 for an Ampeg PF20T preowned in mint condition. No way I'd be paying $400 just to retube its preamp section. Just doesn't make sense to me.

 

[Chuck M]

I should have mentioned that most of the tubes I bought online were not NOS. Most were listed as used but I purchased ones that had been tested. I also have a tube tester and checked to verify readings.

The Telefunken ECC83 used almost always test as better than new and, as I am sure you know, preamp tubes last for many 1,000's of hours of use.

 

[blr2]

I should have mentioned that most of the tubes I bought online were not NOS. Most were listed as used but I purchased ones that had been tested. I also have a tube tester and checked to verify readings.

The Telefunken ECC83 used almost always test as better than new and, as I am sure you know, preamp tubes last for many 1,000's of hours of use.

Buying used tubes is a lottery. Tube characteristics do not change linearly with use. A tube can measure as new, just to start to deteriorate and fail several months down the road. Also, even the seller is honest about mileage (or even knows the history) of the tubes, where and how the tube has been used is even more important than just stating hours of operation. In starved plate designs, that run the tubes at a fraction of their specified B+ voltage, preamp tubes last practically forever. A tube that has clocked a couple of hundred hours in such circuit is basically as good as new. However, this is not the case for preamp tubes in real tube amps that have been slammed hard into overdrive with boosted signals. These don't last for many thousands of hours. Heavy guitar players know this well.
With power tubes it is even more complicated, since the life is also dependent on the bias and matching.

 

[agedhorse]

Buying used tubes is a lottery. Tube characteristics do not change linearly with use. A tube can measure as new, just to start to deteriorate and fail several months down the road. Also, even the seller is honest about mileage (or even knows the history) of the tubes, where and how the tube has been used is even more important than just stating hours of operation. In starved plate designs, that run the tubes at a fraction of their specified B+ voltage, preamp tubes last practically forever. A tube that has clocked a couple of hundred hours in such circuit is basically as good as new. However, this is not the case for preamp tubes in real tube amps that have been slammed hard into overdrive with boosted signals. These don't last for many thousands of hours. Heavy guitar players know this well.
With power tubes it is even more complicated, since the life is also dependent on the bias and matching.

While some of this information is somewhat true, there are generalities that are not in many (or most) cases.

Tube deterioration (other that defects) is generally fairly linear and predictive. This is true for most tubes, though there tends to be more of a curve to power tube deterioration.

Preamp tubes in sensible designs can last 10,000 hours, even at higher plate voltages and even when driven hard. Short preamp tube life is generally more impacted by poor or short sighted designs that work the tube outside their design limits.

In general, tube life (both preamp and power amp) is more impacted by design choices and bias choices than anything else IMO and IME.

 

[blr2]

Preamp tubes in sensible designs can last 10,000 hours, even at higher plate voltages and even when driven hard. Short preamp tube life is generally more impacted by poor or short sighted designs that work the tube outside their design limits.

Are you sure? My experience, means the experience of the guitar players I've played with, tells me otherwise. Mostly Marshall amps. I don't know how sensible their tube designs are, never had a Marshall amp. My three tube amps are used for home practice and recording only. Low volumes and not driving the front end very hard, so the tubes last long. Guitar players had to change tubes annually.

 

[agedhorse]

Yeah, I'm sure. I have done a LOT of tube performance testing, analysis and aging tests. Additionally, I can look back at the history of tube preamps and amps I have designed and been involved with, which produces real world aging data based on large production volumes rather than anecdotal stories.

If only guitar players changed their underwear as often as they changed their tubes, we would all be happier

There is a level of obsession that exists in the guitar market specifically, which is fed by endless marketing and empty promises by those who profit (greatly) from tube sales. Many perfectly good (and tone-full) tubes are discarded every year in the quest for that "perfect" tone that may not in fact exist. '

 

[blr2]

There is a level of obsession that exists in the guitar market specifically, which is fed by endless marketing and empty promises by those who profit (greatly) from tube sales. Many perfectly good (and tone-full) tubes are discarded every year in the quest for that "perfect" tone that may not in fact exist. '

I don't know. I've seen preamp tubes going bad (more than ones) after much less than 10 000 hours of playing. Not discarded because some obsession, just cutting randomly or producing nasty distortion.
I haven't been involved in tube research, testing, design..., just playing music since 1980's. As a sensible person, I'd never pay $100 for a used tube. Same applies for a pair of shoes .

 

[agedhorse]

I don't know. I've seen preamp tubes going bad (more than ones) after much less than 10 000 hours of playing. Not discarded because some obsession, just cutting randomly or producing nasty distortion.
I haven't been involved in tube research, testing, design..., just playing music since 1980's. As a sensible person, I'd never pay $100 for a used tube. Same applies for a pair of shoes .

There are defective tube failures as well, which is different than wearing out. That's NOT what I'm talking about.

 

[blr2]

There are defective tube failures as well, which is different than wearing out. That's NOT what I'm talking about.

I must have been involved with the unluckiest guitar players in the universe then.
Seriously, in real use especially on the road, tubes (and other equipment) are subjected to a lot of mechanical and thermal stress. Don't you think it contributes to wear? I've seen condensation forming on tubes and transformers coming from sub zero to a room temp. We had to postpone sound check, being scared. I've seen amps falling from over 3 ft and all other s*** happening to gear. It's not like burning tubes in a lab rack and measure them once a week. Trust me, being there, done that.
The point is that I'll never, ever recommend to anyone to buy used tubes for over $20 without having confirmed and 100 % true info on their history.

 

[agedhorse]

If you knock your amp over and damage tubes that way, sure they will fail. I'm not sure I would consider that as being unlucky however.

I have plenty of real world experience, 40 years dealing with national and international touring acts on the road. During that time I also designed products for some of the largest amp manufacturers in the US (and still do).

Maybe it's best that we agree to disagree?

 

[blr2]

Maybe it's best that we agree to disagree?

Absolutely, no problem.
With no connection to the above, would you pay $100 for a used preamp 12A... tube? Serious question. In your experience, what the seller should provide in order of info and possibly measurements for you to commit to such a purchase? Again, take my question seriously, please. It may be a useful info, not only for me, but for the others as well.

 

[JimmyM]

Absolutely, no problem.
With no connection to the above, would you pay $100 for a used preamp 12A... tube? Serious question. In your experience, what the seller should provide in order of info and possibly measurements for you to commit to such a purchase? Again, take my question seriously, please. It may be a useful info, not only for me, but for the others as well.

You didn't ask me, but there's no way I'd pay $100+ for a 12ax7 when new ones are so much better than they used to be.

 

[agedhorse]

Absolutely, no problem.
With no connection to the above, would you pay $100 for a used preamp 12A... tube? Serious question. In your experience, what the seller should provide in order of info and possibly measurements for you to commit to such a purchase? Again, take my question seriously, please. It may be a useful info, not only for me, but for the others as well.

No, I wouldn't pay anywhere near that kind of premium for what may very well not be what it's represented to be. Back in the day, it was not uncommon for tube manufacturers to have some "cooperative agreements" to provide component assemblies or even complete tubes to each other when it suited their mutual business interests. There weren't magical attributes placed upon tubes, making them "special" (like unicorn farts). Tubes were a commodity, tubes for industrial, medical and military applications may have had more ruggedized construction, better (and more complete) testing and aging, but consumer grade tubes were just that.