Modern EL34 reliability?

[Enzo]

I hate to hijack the thread but..

When I was a kid, phones were hard wired. The phone had a cord, and the little square box with four screws in it was the hookup. You wanted phones in three rooms, you got three phones. Then they came up with the square four pin plugs. Now you can have one phone and move it around the house. Later they came up with the little plastic RJ connectors we have now. I also remember the four pin male adapter with the RJ jack on the back. You could plug your new-fangled plastic phone cord into the old four pin jack. Pretty high tech.

These days, a commercial phone number might be 1-800-888-9999. No problem on a touch tone, but a real pain in the ass on a dial phone.

[cjenrick]

JJ EL34 unstable at 500, thermal runaway, dropping screen voltage affects tone, no more Mullard metal base tubes, ZZ Top burned them all up in the 70's.

put a fan on the JJ's, or place a 100 ohm 5 watt resistor in between each cathode and ground. this will make things more stable and give you some cool compression.

[pdf64]

I actually have to pick at this a little. 6v6's and 6l6's have been respected by the tube makers WRT their typical operating conditions in guitar amps and there just aren't that many posts about how the new 6*6 tubes suck. But el34's are historically important and tone specific and current production tubes typically DO NOT STAND UP TO THE RIGORS as the 6*6 tubes do. No one wants to modify their Marshall for lower plate voltages, higher value screen resistors and a cooler than tonally optimal bias to accommodate shitty tubes. Something is definitely lost in that scenario. We just want an el34 that works as per the data sheet in amps and designs (vintage or new) that are arranged for that tube model. If a manufacturer can't provide that then they shouldn't be selling the tubes as el34's!!! I'm not at all saying that we can't (or shouldn't) accommodate the new tubes that are available. We do it all the damn time. But if a Marshall can't be operated as a Marshall then a tonal legacy is lost and tube manufacturers eating the dead bones so they can shit money by selling straight up false tubes is disrespectful, lacks any trace of mindfulness and is seriously pissing me off.

I suspect that a key problem maybe that Marshall etc ran EL34 above, sometimes way above, the manufacturer's suggested conditions.
See top of p4 http://www.mif.pg.gda.pl/homepages/f...129/e/EL34.pdf
A 51 watt amp suitable for continuous drive having a HT of 400V, 3k5 primary load, and a shared 1k5 g2 resistor.
IME even back in the early 80s when Teslas were the norm and Mullards were still an option, it could be an expensive exercise putting together a set of reasonably well matched tubes that would survive in a Super Lead or OR120.

[Mick Bailey]

I've found that in amps running higher plate voltages that taming the screen voltage will often provide a much longer lifespan for modern-production EL34s. There are quite a few amps where the screen voltage higher than 500v, so the choice comes down to either finding a tube that will hold up, or reducing the screen voltage via a MOSFET dropper or similar. Increasing the screen resistor to reduce the voltage is counter-productive; a high enough resistance to give a meaningful voltage drop under static conditions plays havoc with the amp dynamics due to the voltage drop when the screen current increases under load.

[bob p]

These days, a commercial phone number might be 1-800-888-9999. No problem on a touch tone, but a real pain in the ass on a dial phone.

My previous house was old. The phone was hard-wired. It had knob and tube wiring too! Over the years that I lived there I converted everything to thinwall conduit. that was back in the days when NEC allowed you to use the conduit as ground.

When I moved to my new c.1957 house in 1970 I thought that the phone system was new-fangled when I saw the phones that could be plugged into those great big 4-pin sockets! I still have several rotary phones with the 4-pin connectors mounted on round jackplate cutouts in the wall. Whenever I need to do an upgrade I convert the round cutouts to modern rectangular boxes, and use multi-port switch plates with RJ-type connectors. Before wireless became available and 10-base-T was considered fast I rewired the whole house with CAT5 cable, simply following the previous owner's layout for the phone system. Now I have an ethernet jack ij the same box next to every phone jack, and at least one in every room.

I never had to buy a cordless phone because my phone guy had wired the entire house with phone cables and loaded the house with phones before cordless phones came along. Similarly, I completely evaded the need for wireless networking because I wired up the entire house for ethernet before wireless came along. Even though I only pulled Cat 5 cable, I still get good gigabit bandwidth, and with a jack every 10 feet in the house I've never felt the need to have wireless.

Dialing 11 numbers is not at all painful if you're used to it. It's when you have to use a phone card that things really start to suck.

[tubeswell]

... No one wants to modify their Marshall for lower plate voltages, higher value screen resistors and a cooler than tonally optimal bias to accommodate shitty tubes. Something is definitely lost in that scenario. ...

This is the issue with this customer. I have tried repeatedly to remonstrate with him about making small changes that will ensure crappy EL34s can work okay in his amp. He is emphatic that the 'handwired' reissue amps wonderfully marketed by Marshall, which he paid gazillions for, should work wonderfully and can't see the problem with just putting in some new tubes and biasing them up. I might just have to give the amps back to him as they are and say 'sorry M8, no can do'.

[Chuck H]

Try the Ruby el34B first. If this is a head amp, and it sounds like it is, I think they'll be good. That is, if this customer can stomach having Chinese tubes in his amp Some players seem to think that if you put Chinese tubes into an amp with something like, say, cloth covered wire a hole opens in the space/time continuum and Cthulhu brings a thousand years of darkness.

[bob p]

I actually have to pick at this a little. 6v6's and 6l6's have been respected by the tube makers WRT their typical operating conditions in guitar amps and there just aren't that many posts about how the new 6*6 tubes suck. But el34's are historically important and tone specific and current production tubes typically DO NOT STAND UP TO THE RIGORS as the 6*6 tubes do.

Well, to be fair, an EL34 is a true pentode, while 6v6, 6L6 and KT-77 etc. are beam tetrodes. There’s a fundamental difference in the way that those variants operate that renders such a direct comparison unfair.

The EMI design for the beam tetrode provides screen grid current that’s about 5-10% of the anode current, while a true pentode’s screen grid current is on the order of 20% of the anode current. We tend to forget how the construction and electrical properties are different. Maybe one of the reasons that EL34 aren’t as robust as 6L6 is that pentodes by design suffer 2x–4x more much screen current at identical anode voltages, all other things being equal. This is the reason that it’s so important to keep a handle on screen current with EL34. To refuse to pay close attention to screen current is suicidal. Pentodes just can’t take the kind of screen abuse that beam power tubes can take, and everyone who insists on turning a blind eye to that fact is going to get burned.

No one wants to modify their Marshall for lower plate voltages, higher value screen resistors and a cooler than tonally optimal bias to accommodate shitty tubes. Something is definitely lost in that scenario. We just want an el34 that works as per the data sheet in amps and designs (vintage or new) that are arranged for that tube model. If a manufacturer can't provide that then they shouldn't be selling the tubes as el34's!!!

Philosophically I’m right there with you, Chuck – but being a pragmatist in a changing world I have to adapt and be flexible so I don’t get kicked in the teeth (very often).

Enzo made a good point --

It is another thing from the past that just isn't as good as the originals. I doubt they will get better.
...
I wish modern tubes worked as well as the days of RCA and Sylvania, but they don't.

Tubes in 2017 aren’t what they were in 1970. They can’t be as good, they never will be as good, and things are only going to get worse. It’s a sad truth, but it’s a truth nonetheless. The major players that were responsible for the great advancements in tube technology, like GE, RCA, Sylvania, Tung Sol, EMI/GEC/MOV, Genalex, Mullard, TeleFunken, Tesla… they’re all gone. For the most part nothing is left of them but the names. The great names from each country that competed to drive technology forward during the Golden Era have abandoned the technology and left the market to the second-tier players. Most of those second tier companies have had their problems as well. EI was nearly bombed out of existence by UN Peacekeepers. Tesla was broken apart and the parts were sold away to private investors. SED quit the business because it was no longer profitable. Now all that’s left are a few of the also-ran producers who were never at the forefront of design or quality control. They face no serious competition and they can do whatever they want. Right now we’re at the mercy of Chinese suppliers who really don’t give a damn about quality and never will.

But if a Marshall can't be operated as a Marshall then a tonal legacy is lost ...

It was a fun ride while it lasted, but the writing is on the wall. The Marshall tonal legacy *IS* becoming lost, and it’s only going to get worse. We have to face the fact that that tonal legacy was great in our youth, that someday it will only exist on records, and that right now we're caught somewhere in between. We’re at the point in the tube era where we are all trying to scrape together the remains of abandoned technology to keep it going. We live in a scavenging society because new tubes just aren’t as good as the old ones. Nobody is left at JJ who manufactured tubes in the Golden Era of Tesla, now the lines are run by young workers who will never know as much as the old workers knew. Knowledge has become lost. We have the same problem here – NASA can’t even build a Saturn V rocket today because all of the knowledge died with the old engineers.

Given the shape of the current tube market I’ve been thinking that we’re just like the scavenging mechanics in Cuba who are trying to propel a motor vehicle economy by scavenging parts for cars that were made in the 50s. The situation is only going to get worse. We have no choice but to adapt to it as best we can.

I think that the take home lesson is that you’re just not going to be able to run a vintage plexi on new tubes, and that it’s foolhardy to buy a handwired reproduction when the new tubes won’t work in it either. There aren't parts to make the circuit work properly without modification, so the original circuit is now dead unless you have money to throw at a stockpile of NOS tubes.

What are we to do? One option is to gripe. Another option is to adapt the circuits to get the best results that we can based on the parts that are available today. Yeah, modding the circuit sucks, but it's better than the alternative of having no other option beyond the "Plexi" setting on a modelling amp.

[tubeswell]

... We’re at the point in the tube era where we are all trying to scrape together the remains of abandoned technology to keep it going. We live in a scavenging society because new tubes just aren’t as good as the old ones. ...

Speaking of which, these just arrived in the mail from the UK 5 mins ago by courier - an 'untouched' ;-) quad of Sovtek EK34G*! Will these do the thing? Time will tell

Any bets on which will make the best P-P pairs in a superlead100? (I'm going to have to spend some time burning them at 500V methinks)

(And which ones on the non-inverting side of the PI? LoL)

*If these don't work, I'll try the ST EL34BHT - and if those don't work, That's it!

[Tom Phillips]

Speaking of which, these just arrived in the mail from the UK 5 mins ago by courier - an 'untouched' ;-) quad of Sovtek EK34G*!...

Porn request. Please show us the goodies under the box.

[Randall]

I try to keep a pair of the most common tubes on hand. 6L6, 6V6, EL34, EL84, 12AX7, 12AT7, and a couple of rectifiers. I use mostly JJs, except for rectifiers. When I get a dud that is out of warranty, I simply order another. When the replacement arrives I return the bad out of warranty one. The vendor thinks it is the one they just sent me, but who cares? They sold me a bad tube, and I want it replaced. When this happened with back to back JJ GZ34s a while back, I switched to Ruby.

[tubeswell]

Porn request. Please show us the goodies under the box.

here ya go

[diydidi]

I have found that when repairing guitar amps using modern production tubes it is sometimes necessary to up the screen grids.
If the screen voltages is to similar in voltage to the plates this is a must IMHO.

[soundmasterg]

Speaking of which, these just arrived in the mail from the UK 5 mins ago by courier - an 'untouched' ;-) quad of Sovtek EK34G*! Will these do the thing? Time will tell

Any bets on which will make the best P-P pairs in a superlead100? (I'm going to have to spend some time burning them at 500V methinks)

(And which ones on the non-inverting side of the PI? LoL)

*If these don't work, I'll try the ST EL34BHT - and if those don't work, That's it!

Sovtek EL34G's were not very good back in the day and they are likely just as bad now. My brother had a pair in a new Sovtek MIG 60. They came stock in that amp, and that amp had somewhere around 620V B+. The tubes failed within 2 months of use, sucked a hole in the glass from the inside and smoked. Amp was sent back under warranty, tubes were replaced with another pair of EL34G's, and the amp was traded for a vintage Silvertone 1484 ASAP. I hope they will work for you, but I doubt if they will.

Greg

[bob p]

When I see high B+ and high dissipation, I automatically think "fan". Lots of high power amps use them, it helps. It's also a cheap upgrade. The problem is that budget amp manufacturers won't even consider adding a fan due to cost.

I have one of those old Silvertones. They don't have a high B+ and they're not biased hot.