I have been looking at the mullard EL34 datasheet and I was very suprised about what I have found. Well I always knew it was there but I actually wonder, has anyone gone as far as trying this out ?
Fixed Bias
Ua 800V
Ra-a 11k
Pout 100W!!!
I dont know what kind of maniac would do this. Some guy at the mullard test lab has gone bonkers probably 😀
Regardless it would be fun to see someone actually try it. It seems unreallistically insane. Also I would really hesitate to trust any socket at those voltages. You end up with essentially double the anode voltage on either side and that puts to the test any octal socket in these conditions.
If this could safely pull off 100W in a single pair would be interesting to see what kind of numbers it could pull off as in a HiFi circuit.
Heres the datasheet.
Operating conditions for two valves in push pull on page 3.
http://www.r-type.org/pdfs/el34.pdf
Fixed Bias
Ua 800V
Ra-a 11k
Pout 100W!!!
I dont know what kind of maniac would do this. Some guy at the mullard test lab has gone bonkers probably 😀
Regardless it would be fun to see someone actually try it. It seems unreallistically insane. Also I would really hesitate to trust any socket at those voltages. You end up with essentially double the anode voltage on either side and that puts to the test any octal socket in these conditions.
If this could safely pull off 100W in a single pair would be interesting to see what kind of numbers it could pull off as in a HiFi circuit.
Heres the datasheet.
Operating conditions for two valves in push pull on page 3.
http://www.r-type.org/pdfs/el34.pdf
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That’s going to be an expensive output transformer, for an experiment that might very well go szhekx in the night. There were early PA amps that ran on these voltages (as high as 900 at light load) that didn’t exactly have the best track record - they were being discussed in another thread recently.
Plenty of sweep tubes out there with 900V continuous plate rating and 25+ watt dissipation. With anode caps so you don't worry about your ceramic socket arcing over. Some of them still run $3 to $5. I’d trust them more with a project like that.
Plenty of sweep tubes out there with 900V continuous plate rating and 25+ watt dissipation. With anode caps so you don't worry about your ceramic socket arcing over. Some of them still run $3 to $5. I’d trust them more with a project like that.
Id still like to see a pair of EL34s completely thrashing at 100W output power. I would be incredibelly conscious about having a load on the output. No load means cracked ceramics 😀
I think the consensus was that even the original Mullard had problems at 800 volts.
Light shows are fun, though.
Light shows are fun, though.
The Siemens 6 S ELA 2796 amplifier has 6 EL34's running with almost 900 V at the anodes and almost 460 V at the screen grids (under no signal condition; the voltages will ofcourse sag with signal) to produce 250 Watt.
https://www.klangfilm.org/index.php?lng=0&music=&type=0&frame=3&item=&title=6S-Ela-2796&dir=data/pictures/electronics/amplifiers/6s-ela-2796/&num=1
There are more examples of professional amplifiers running EL34,s with 800 V or higher at the anodes.
I don't know about any consensus on what the original EL34's could withstand. For me, one forum member again and again stating that at Mullard EL34's died constantly under these circumstances, is not consensus. And if this claims would be true, why couldn't the Mullard engineers fix that problem by some modifications to the amplifier? How likely is it that they kept on replacing EL34's instead?
The fact that companies like Siemens produced professional amplifiers like the 6 S ELA 2796 to me indicates that (at least part of) the EL34's produced in those times could withstand these circumstances.
https://www.klangfilm.org/index.php?lng=0&music=&type=0&frame=3&item=&title=6S-Ela-2796&dir=data/pictures/electronics/amplifiers/6s-ela-2796/&num=1
There are more examples of professional amplifiers running EL34,s with 800 V or higher at the anodes.
I don't know about any consensus on what the original EL34's could withstand. For me, one forum member again and again stating that at Mullard EL34's died constantly under these circumstances, is not consensus. And if this claims would be true, why couldn't the Mullard engineers fix that problem by some modifications to the amplifier? How likely is it that they kept on replacing EL34's instead?
The fact that companies like Siemens produced professional amplifiers like the 6 S ELA 2796 to me indicates that (at least part of) the EL34's produced in those times could withstand these circumstances.
Original EL34 could have the full 800 volts. At Amplifiers with valves you see an amp that is build with 24 EL34 an had a peak power of almost 5 Kw.
Which is what they attempted in the Mitcham factory and probably in Blackburn also.
The thing was constantly blowing up.
The idea was to set out to prove Mullard could use their own valves for making their own factory PA systems.
Being as they weren't capable of making anything even close to as reliable design as any decent beam tetrode, they desperately had to prove a pentode (based on the 1940s EL37) could do the job.
FAIL
Why anyone would want to try to compete with the industrial might of GEC-RCA-Sylvania totally beats me.
The British (and Dutch) have been fond of failure for decades. (witness the attempts by philips to prevent people copying first the compact cassette then the Audio CD, and overcharging massively for royalties!), or the Philips ECG attempted production of Sylvania stuff...
Definition of insanity is attempting the same experiment time and time expecting different results.
QED.
Luckily the Russians were not so stupid, which is why they are still manufacturing by the 1000s today.
The thing was constantly blowing up.
The idea was to set out to prove Mullard could use their own valves for making their own factory PA systems.
Being as they weren't capable of making anything even close to as reliable design as any decent beam tetrode, they desperately had to prove a pentode (based on the 1940s EL37) could do the job.
FAIL
Why anyone would want to try to compete with the industrial might of GEC-RCA-Sylvania totally beats me.
The British (and Dutch) have been fond of failure for decades. (witness the attempts by philips to prevent people copying first the compact cassette then the Audio CD, and overcharging massively for royalties!), or the Philips ECG attempted production of Sylvania stuff...
Definition of insanity is attempting the same experiment time and time expecting different results.
QED.
Luckily the Russians were not so stupid, which is why they are still manufacturing by the 1000s today.
You are certainly BITTER about Philips,and all of its worldwide branches.
Was your supposed father who supposedly worked there fired or something?
And you spent half your life absorbing that hate?
Ease off man!
There´s more to Life than constantly feeding old grudges!!!!
Philips was present all over the World, typically DOMINATING local Electrical related markets, specially around lamps of all kinds but also tubes capacitors, speakers, consumer products (from TVs to electric shavers and everything in between) etc. , and installing Factories in every Country, such a Miniwatt, Mullard, FAPESA, IBRAPE, VALVO, etc.
Try that "GEC-RCA-Sylvania"
Maybe being in a hermetically closed , technically backwards for decades Communist system "market" helped them stay alive, while 95% of Tube factories worldwide closed because of OBSOLESCENCE and simple lack of market and profitability.
I wouldn´t BRAG about that.
Geloso G280A had 1000 V as + Ub.
G280A Ampl/Mixer Geloso SA; Milano, build 1958, 4 pictures
Bollettino Tecnico Geloso
G280A Ampl/Mixer Geloso SA; Milano, build 1958, 4 pictures
Bollettino Tecnico Geloso
The 100W/800V application with 2xEL34 could be found in Valvo (Philips) Handbuch of 1962 as well. Even at that time this was considered troublesome. Serious British guitar amps of that era used 4xEL34 to achieve 100 Watts.
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I guess it was the space race of the audio industry - to get to the benchmark of 100 watts with a single pair of valves. The only way to get the necessary efficiency at the time was with a high enough B+ and corresponding impedance - for all intents and purposes, tubes are “Rds-ON” limited. Transmitting triodes run 24/7 at even higher voltages, right? But the construction techniques in the equipment are different, and they’re willing to spend a few dollars making an RF transmitter safe and reliable. The game has to be stepped up on EVERYTHING, not just the two output tubes. Making a good hi-fi quality 11k 100 watt transformer is much harder than say a 5k. Equivalently built, the 5k will run higher (and lower!) in frequency.
The KT88 and it’s derivatives was a better way to attack the problem - sacrifice efficiency to run at a more reasonable 600 volts. Requires a higher dissipation capability, but a lot of the other failure mechanisms are more easily mitigated.
If I was intent on getting 100 watts out of a single pair I wouldn’t use either. I’d switch to horizontal output tubes. That brings the price of success or failure way down. Two pair of just about anything is a better solution still - glass is cheap compared to iron at even new production prices. You can only push just so much power at whatever bandwidth you’re interested in through a given dollars worth of iron and copper. Output transformers saturate, and power transformers sag. Those put limits on the watts out. So does the emission capability of the tubes, but adding more there is way cheaper than adding more iron. To use a solid state analogy, adding another pair of output transistors won’t change the output power, but doesn’t double the cost either. But less likely to blow up.
The KT88 and it’s derivatives was a better way to attack the problem - sacrifice efficiency to run at a more reasonable 600 volts. Requires a higher dissipation capability, but a lot of the other failure mechanisms are more easily mitigated.
If I was intent on getting 100 watts out of a single pair I wouldn’t use either. I’d switch to horizontal output tubes. That brings the price of success or failure way down. Two pair of just about anything is a better solution still - glass is cheap compared to iron at even new production prices. You can only push just so much power at whatever bandwidth you’re interested in through a given dollars worth of iron and copper. Output transformers saturate, and power transformers sag. Those put limits on the watts out. So does the emission capability of the tubes, but adding more there is way cheaper than adding more iron. To use a solid state analogy, adding another pair of output transistors won’t change the output power, but doesn’t double the cost either. But less likely to blow up.
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If you want to operate an amp like this Siemens, East German (RFT) EL 34 tubes can stand the voltage.
And all you got, after spending mucho greenbacks, going from 50W to 100W was 3dB. Nature is cruel sometimes.
I have never taken a pair of EL34's past 70 watts and that was iffy due to the poor quality of new production tubes. I have taken old Sovtek 6550WA's to 100 watts per pair on 3300 ohms and just for fun I took a pair of early 90's vintage Shuguang KT88's to 100 watts in the same setup without an explosion.
I had purchased a box of over 100 of those tubes from Stan at ESRC for cheap (under $2 each). He got some, then refused to sell them because they were very poorly made. I had one spark out so bad that the glass cracked, and it was in a 35 watt per pair HiFi amp. I tested every tube at progressively higher powers and kept the good ones. I think there were 5 or 6 that worked at 100 watts out of over 100. Some didn't work at all.
As wg_ski stated, I use TV sweep tubes for all big amps. the 6LW6, 26LW6, 36LW6 and 26HU5 will all go past 200 watts per pair and a well made tube can run at 250 watts per pair with a 2500 ohm load on 650 volts.
Been there, blown that when my stack of Radio Shack dummy load resistors blew open. I now have a pair of 8 ohm 500 watt resistors and I have seen them smoking, twice! It took 4 tubes on 650 volts to do it though. 4 X 35LR6 the first time several years ago, and 4 X 26HU5 the second time a couple months back.
I had purchased a box of over 100 of those tubes from Stan at ESRC for cheap (under $2 each). He got some, then refused to sell them because they were very poorly made. I had one spark out so bad that the glass cracked, and it was in a 35 watt per pair HiFi amp. I tested every tube at progressively higher powers and kept the good ones. I think there were 5 or 6 that worked at 100 watts out of over 100. Some didn't work at all.
As wg_ski stated, I use TV sweep tubes for all big amps. the 6LW6, 26LW6, 36LW6 and 26HU5 will all go past 200 watts per pair and a well made tube can run at 250 watts per pair with a 2500 ohm load on 650 volts.
No load usually means a fireball inside your OPT!
Been there, blown that when my stack of Radio Shack dummy load resistors blew open. I now have a pair of 8 ohm 500 watt resistors and I have seen them smoking, twice! It took 4 tubes on 650 volts to do it though. 4 X 35LR6 the first time several years ago, and 4 X 26HU5 the second time a couple months back.
Bogen didn't put todays Chinese tubes in them.
You don’t even need the biggest sweep tubes to make 100 watts. The 24 watt types will do it, and the 17.5 and 18 watters will get you “maddeningly close”. Some of those 18 watt compactrons will do over 100 on paper, but I can’t vouch for long term reliability as the power dissipation required at quiescent is about 26 watts each. Two pair of $3 each types will get you there easily, as you lower vg2 and the required standing current to get clean sound drops.
The low Iq required to get 100W out of EL34’s at 800 volt plate doesnt exactly help the sound either. I can get low crossover distortion out of 6550’s at only 20 watts idle - if g2 kept around 300. At 400, 500 on g2 it takes more to clean it up.
You don’t even need the biggest sweep tubes to make 100 watts. The 24 watt types will do it, and the 17.5 and 18 watters will get you “maddeningly close”. Some of those 18 watt compactrons will do over 100 on paper, but I can’t vouch for long term reliability as the power dissipation required at quiescent is about 26 watts each. Two pair of $3 each types will get you there easily, as you lower vg2 and the required standing current to get clean sound drops.
The low Iq required to get 100W out of EL34’s at 800 volt plate doesnt exactly help the sound either. I can get low crossover distortion out of 6550’s at only 20 watts idle - if g2 kept around 300. At 400, 500 on g2 it takes more to clean it up.
Long time ago I made ~200W AM transmitter modulator with four EI-Nis EL34 tubes , with 800V at anodes and 400V on g2 , it was not easy to tame that beast , those cheap ceramic sockets bangs in pieces like firecrackers until I have mounted the real quality ones , any way , except real good quality ceramic octal tube sockets man have to keep Rg1 low as possible , main transf. 6,3V~ heater single secondary winding for 4xEL34 tubes have to be very good isolated from other secondaries and to stay non earthed ,also electrically floating just to avoid arcing in beetwen pin 3 (anode) and pin 2 (heater) , after these measures that modulator worked just fine , later I have switcted to four EI-Nis KT90 without noticable difference in modulator performance ,
with different new production EL34 I will not exceed about 600V on anodes and 300V on g2. ,
IMHO for the best dynamics of sound those EL34 and many other simmilar tubes (KT77 ,KT88,KT90 ,6550, ...) have to be used in that PP- AB1 class pentode mode with anode B+ about 600-650V and g2 voltage in half of that , 300-325V .
with different new production EL34 I will not exceed about 600V on anodes and 300V on g2. ,
IMHO for the best dynamics of sound those EL34 and many other simmilar tubes (KT77 ,KT88,KT90 ,6550, ...) have to be used in that PP- AB1 class pentode mode with anode B+ about 600-650V and g2 voltage in half of that , 300-325V .
I have a professional Siemens PA amp from the late 50s (6S Ela2798).
The power stage uses 2xEL34s operated as per datasheet example (B+ ca. 850V, Vg2 ca. 430V)
Has idle current meter and trim pots on the front panel to individually adjust idle currents to 25mA.
Still works fine and puts out around 100Vrms into a 100R load before clipping.
Built like a tank, full steel housing.
It's interesting to note that the datasheet calls this operation class B, while plate dissipation is 20W or 80%.
The power stage uses 2xEL34s operated as per datasheet example (B+ ca. 850V, Vg2 ca. 430V)
Has idle current meter and trim pots on the front panel to individually adjust idle currents to 25mA.
Still works fine and puts out around 100Vrms into a 100R load before clipping.
Built like a tank, full steel housing.
It's interesting to note that the datasheet calls this operation class B, while plate dissipation is 20W or 80%.