Well, the original EL34 I think is fair to describe as one of the early or first attempts at a cost-effective power pentode. It was meant to be a useful 'kinkless tetrode' type of tube.
It was quickly superceded in quality by the 6L6, itself a low-voltage version of the 807 / 1625.
Many el34s were pushed into doing more than they were really capable of handling, and part of their reputation was blackened by the many tube failures in circuits that ran them too hot and at too high a voltage.
That having been said, they are still popular as guitar-amp tubes. However, if you want an inexpensive low-voltage power-tube, the 6L6 is the peak of that line of development. Its also a better tube, designed from the lessons learned in earlier models.
In my view, the EL34 is not a good hi-fi tube really though, due to reliability issues and problems most importantly with the alignment of the grids. However, the American version was made to be a higher power version, and it was better made than foreign versions.
The EL34 and 6CA7 are not equivalent. The American tube is better.
A true power beam tetrode aligns all the grids properly so that there is little leakage into the screen grid circuit. Also, big tetrodes like the 6L6GC were designed to handle more grid current (and higher voltages via spacing design).
My preference is a 6L6 type tube, for quality reasons. Its not really the coloration issue, since in my designs I strive for colorless operation.
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By what metric do arrive at that conclusion? What are the possible negative consequences of sharing more, or all, in this case?
Utterly nonsense.
The EL34 is a high quality pentode, designed by Philips especially for audio, like the EL84.
In its original "shape and spec" it was made by Philips, AEG, Telefunken, Siemens and Mullard, and the original specifications were very well met.
Later productions (Chinese, Russian) simply did not have the same quality, and reliability/specification issues relate to these productions, not the original versions which are difficult to find now.
Well that depends in part upon your worldview and philosophy.
For practical purposes, a few proverbs will give the short answer.
Nothing's ever really free or easy.
Sometimes they shoot the messenger,
especially when personal illusions are threatened.
Vested interests don't take kindly to market adjustments due to shattered illusions.
Whistle-blowers aren't usually appreciated, let alone rewarded,
even when their necessity is acknowledged.
Even Jesus had something to say about this:
"Don't cast pearls before swine:
They'll just trample them."
Speaking of Jesus, I'm not a saint,
and I'm not ready for the level of commitment required by martyrdom.
So there I'll have to pose some reasonable limits for my own protection.
Nothing convincing here.
The Pinto was designed by Ford, especially to be a good economy car.
...Well, to quote yourself:
You can't have your cake and eat it too, friend.
There are no EL34s of the kind you speak,
unless you are a hoarder of dwindling rarities.
In the real world, (Chinese etc) El34s suck.
Nazaroo,
Your last week attempts to "derail" the Aikido circuit failed miserably, and the thread was closed by moderators action.
Reading these "new" pages on the mu follower it is once again clear that you actually have very little to contribute; your circuit is far from "original" and the fact that you come up with it with that much aplomb is not helping either.
What is your real goal here, also because you seem to refuse to "share too much"?
Your last week attempts to "derail" the Aikido circuit failed miserably, and the thread was closed by moderators action.
Reading these "new" pages on the mu follower it is once again clear that you actually have very little to contribute; your circuit is far from "original" and the fact that you come up with it with that much aplomb is not helping either.
What is your real goal here, also because you seem to refuse to "share too much"?
Oh oh, more sour grapes from the Aikido crowd.
I've given not only the circuit diagram,
but also detailed instructions on how to build almost any version of my topology.
My real goal then, is self-evident:
To fully share a useful design.
As for your opinion of this thread,
my thread here has 4,500 hits in 2 days,
while your Aikido thread has only 3,000, or so,
and that one has been going for weeks and weeks.
Plainly many people think this thread is very interesting,
educational, and entertaining, as opposed to your claim
that it has 'very little to contribute'. People vote with their feet.
Why not just enjoy and observe?
Why all the negativity?
peace
Nazaroo
nazaroo;3040127 Plainly many people think this thread is very interesting said:
IMO we don't need any education on the mu follower; is already described in length in the past. You are repeating and claiming to be "original".
For the majority of tube guys here I think your contribution is entertaining for a very short while (like your Aikido thread) but then becoming annoying (like your Aikido thread).
Pieter, it's probably not worth throwing gas on the fire to put it out.
As for the EL34 not being a good audio tube, I don't know many who would turn down a mint Marantz 9. I sure wouldn't, even though I don't use EL34 in my own designs.
As for the EL34 not being a good audio tube, I don't know many who would turn down a mint Marantz 9. I sure wouldn't, even though I don't use EL34 in my own designs.
This forum has every level of reader,
and sometimes one explanation serves one person better than another.
So far you're the only negative poster in 80 posts, and 4,000 reads.
Lighten up man.
I am not your enemy.
As the Moderator says, lets aim for peace.
I don't use EL34 in my own design because it is currently overpriced, while Gu-50 is under-priced. But I have to admit, EL34 would be easier to use because it is happy on lower anode voltages and lower anode load resistances.
The EL34 was actually towards the end of a line of output pentodes developed by Philips. Far from being a "useful kinkless tetrode", the kinkless tetrode was invented by MOV as a way to produce a similar valve without violating Philips' patents. The KT was a 'useful pentode'! As often happens in technology, the second solution turned out to have some advantages over the original. For some reason MOV decided to licence the idea to their American partners at RCA and the 6L6 was born. The 807 was derived from the 6L6; you seem to imply the opposite.nazaroo said:
You are free to hold whatever opinion you wish on the merits of particular valve types, but don't rewrite history! See EL34 Story for an interesting account in German.
I have far more ideas than I have time right now. I still have my full time engineering job (40 years in the same company) which leaves very little time for Tubelab right now. In fact my soldering iron hasn't been hot yet this year. I have several boards laid out in my computer that I haven't had the time to make, so I'll have to pass. I laid out a PC board for a simple amp back in 2008. Even had the time to build one. A few people have been persistently twisting my arm to turn it into a Tubelab product, so It's next in line.
I tinkered with the SRPP and the Mu-follower and a few of my own variations for use as output stages several years ago. I felt that the low efficiency and high power supply voltages were deal breakers. Where I live heat is a big deal. I built a 40 WPC SE amp using 845's about 8 years ago. It hasn't been turned on in 4 or 5 years due to the heat output. It is currently 97 degrees F outside, so I play my 2 WPC 45 amp most of the time.
Nelson Pass has been doing this with some of his mosfet based SE designs. I believe he has a patent on a modulated CCS that is the top device in a SE mosfet amp.
The 6L6 was released in 1939. It preceeded the EL34 which was released in 1953. The European EL34 was a true pentode. The KT66, KT77 and KT88 were the Kinkless Tetrodes (beam tetrodes). The 6L6, 6L7G, 6L6GA all came first.
The 807 and the 6BG6 ARE 6L6GA's with the plate brought out to a top cap. This eliminates the close spacing between the plate (pin 3) and the heater (pin 2) that is the reason for the plate voltage limitation on the 6L6 types. The 807 and 1625 (and a few others) were 6L6GA's repackaged for RF use. I have taken several broken ones apart and proved (to myself at least) that all of the WWII vintage (and older) 807's contained 6L6GA guts with a shield in the base on some tubes. The 6BG6 and 6BG6G was created for TV sweep tube use. So was the 6BD5. The older tubes all contained 6L6GA guts.
As tube production waned and assembly lines were shut down many manufacturers stuffed the glass with whatever thay had. There were plenty of 807's and 6BG6's made with 6L6GC guts. The 6L6GC has a larger plate and a higher dissipation rating. This plate will not fit into the tiny 6BD5. All 6BD5's contain 6L6GA guts. At the end of the tube era Sylvania/Phillips stuffed some 6BG6GA tubes with 7027A's. These tubes are the hot ticket for a big amp, but are getting scarce.
See this page (I have no relationship with SND):
6BG6 To 6L6 Vacuum Tube List
The original Mullard EL34 was a very good tube. The grids were properly aligned and they worked quite well in a HiFi amp. All were true pentodes. These tubes sell for stupid money today.
There is lots of "stuff" out there today sold as EL34's. Most are true pentodes, but few have properly aligned grids. Some work good in a HiFi amp, while others don't. I can say the same thing about 6L6GC's too. There are plenty of junk 6L6GC's out there.
The 6CA7 was supposed to be the American type number for the EL34. In the 60's many American branded EL34's were made in Europe and were true pentodes. I know that there were some beam tetrodes sold as EL34's. The late production Sylvania's were beam tetrodes bearing no resemblance to the European EL34. I have some that say 6CA7 / EL34 USA and are beam tetrodes that look more like a KT77 than anything else. They are much larger than the skinny EL34.
Thanks for everyone's input on the EL34.
Its a bit off topic, but I'll still weigh in with Wavebourn on this:
Preferences are in part based on economics,
and pricing changes preferences.
Right now for myself, I seem to be able to get a 6L6 at reasonable cost.
If that were to change, who knows?
Maybe I would try an EL34, or at least design to allow either.
Its a mistake to think I have something personal against a tube.
Any tube is better than no tube.
Luckily few of us have to settle for 'any tube'.
We can all pick and choose and have fun doing it.
Lets get back on topic.
Its a bit off topic, but I'll still weigh in with Wavebourn on this:
Preferences are in part based on economics,
and pricing changes preferences.
Right now for myself, I seem to be able to get a 6L6 at reasonable cost.
If that were to change, who knows?
Maybe I would try an EL34, or at least design to allow either.
Its a mistake to think I have something personal against a tube.
Any tube is better than no tube.
Luckily few of us have to settle for 'any tube'.
We can all pick and choose and have fun doing it.
Lets get back on topic.
I remember the story that 6L6 was derived from 807 that was designed as a military transmitting tube.
Speaking of "Kinkless tetrode", it is not the same as "Ray tetrode". Ray tetrode contained 5'th electrode in form of ray forming blinds, in order to avoid royalties for the additional grid used. While kinkless tetrode is a fair tetrode in which the kink is removed by geometry, without additional "5'th wheel".
Speaking of "Kinkless tetrode", it is not the same as "Ray tetrode". Ray tetrode contained 5'th electrode in form of ray forming blinds, in order to avoid royalties for the additional grid used. While kinkless tetrode is a fair tetrode in which the kink is removed by geometry, without additional "5'th wheel".
Thank you for your input to this thread.
And your considerate explanation for your decline on the circuit boards. Your contributions are always appreciated in my threads.
I understand the 'deal-breaker' issue, and the problem of climate with tubes. If I was further south, I'd be looking for cooler operation too.
In Canada of course, an amp that doubles as a room heater is a coveted miracle...
P.S., if someone wants to build a Ju-Jutsu amp with EL34s, I'll be happy to help.
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On the Power Supply,
if you add the isolation legs as shown,
the PS can be used for either configuration of amp,
Push-Pull Monoblock or SE Stereo amp.
The differences will be on the Amp chassis:
if you add the isolation legs as shown,
the PS can be used for either configuration of amp,
Push-Pull Monoblock or SE Stereo amp.
The differences will be on the Amp chassis:
In the monoblock version, the difference on the Amp chassis,
will be this:
You can either remove one Output transformer,
or just wire the secondaries in parallel (test polarity),
and lift the ground on the primary.
You can put a simple switch in the Power Supply too,
to bypass the 2nd cap in the output for monoblock mode.
For the input you can drop in the balanced input jack
and the Jensen Input transformer.
Try a JT-11P-1T for instance:
It should be able to handle your hottest input signal.
you can get specs of the JT-11P from Jensen here.
Dual inputs can be switched in and out with a switch.
will be this:
You can either remove one Output transformer,
or just wire the secondaries in parallel (test polarity),
and lift the ground on the primary.
You can put a simple switch in the Power Supply too,
to bypass the 2nd cap in the output for monoblock mode.
For the input you can drop in the balanced input jack
and the Jensen Input transformer.
Try a JT-11P-1T for instance:
It should be able to handle your hottest input signal.
you can get specs of the JT-11P from Jensen here.
Dual inputs can be switched in and out with a switch.
Attachments
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Can you show a schematic of how an SE output transformer would be connected from the mu-follower output to ground without a coupling cap?
This can't be done while simultaneously leaving the ground connection attached.
Here are some of the options:
(1) The transformer upper end can be connected to B+,
but this defeats the PSRR of the top tube, reintroducing PS noise into the circuit.
If the PS is already clean and solid, this can be minimal,
i.e., no worse than any other SE design.
(2) The transformer can be connected to a voltage-divider network,
but this re-applies about half the PS noise to the output tube, through the tranny.
From there you could try some of the Aikido-style tricks,
since the Output circuit is unusual in that it is more or less CCS.
This is why I prefer my original design, push-pull,
with no DC or PS noise applied to the transformer at all.
I merely mention some of the interesting options,
if you attempt to run my circuit as an SE instead of a PP Monoblock.
I suggested building it as an inexpensive test-run,
for those who prefer SE and wish to try the circuit inexpensively.
If they like it, they should proceed to step B, building two,
and reconfiguring to monoblocks.
Its still a good SE circuit without the output cap,
but its not utilizing all my design advantages.
I did not name it "the Ultimate SE",
even though it is a great SE circuit,
because I prefer PP for the clean power you get with my design.
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