The 6J5GT is available in round and flat anodes. I have both. I prefer the sound of the round anodes, but this is subjective and as FlaCharlie says, there may be other factors involved.
I think tube construction and geometry is fascinating. I wish I knew more about it. I've followed TM's many deconstructions of tubes in his "Tube of the Month" blog with great interest. Here's his deconstruction of a 6J5GT
https://vinylsavor.blogspot.com/2013/03/tube-of-month-6j5.html
I think tube construction and geometry is fascinating. I wish I knew more about it. I've followed TM's many deconstructions of tubes in his "Tube of the Month" blog with great interest. Here's his deconstruction of a 6J5GT
https://vinylsavor.blogspot.com/2013/03/tube-of-month-6j5.html
Since "exceptional linearity" is claimed, it should be easy to be proven.
All it takes is an input/output graph, complemented by a distortion measurement.
High linearity=low distortion.
That such easy to get data is hidden, hints at it being no more than salesman's babble / snake oil / B.S.
So far all I read here is unsubstantiated statements with nothing backing them.
All it takes is an input/output graph, complemented by a distortion measurement.
High linearity=low distortion.
That such easy to get data is hidden, hints at it being no more than salesman's babble / snake oil / B.S.
So far all I read here is unsubstantiated statements with nothing backing them.
I think it's uninformed and tacky to design a tube, claim it sounds better but not offer it for sale or publish its 3rd party measured specs. Most of us that design and build our own amps are not that gullible. Besides, nobody has offered any data that suggest round plates constitute a more linear performance than oval or rectangular. Lots of words and theories, yes, but no data.
https://frank.pocnet.net/sheets/127/7/76.pdf
https://frank.pocnet.net/sheets/127/6/6P5GT.pdf
And from Thomas webpage the 6N7 actual curves:
http://vinylsavor.blogspot.com/2020/10/tube-of-month-6n7-revisited.html
All detractors, please find equal or better indirectly heated triodes.
And it's not just about linearity. Where they are not very linear anymore, they tend to have less high order harmonics. Everyone can try it with available round plate tubes.
No need for TM to prove anything. If one wanna know can buy his amps....
https://frank.pocnet.net/sheets/127/6/6P5GT.pdf
And from Thomas webpage the 6N7 actual curves:
http://vinylsavor.blogspot.com/2020/10/tube-of-month-6n7-revisited.html
All detractors, please find equal or better indirectly heated triodes.
And it's not just about linearity. Where they are not very linear anymore, they tend to have less high order harmonics. Everyone can try it with available round plate tubes.
No need for TM to prove anything. If one wanna know can buy his amps....
absolutely within your rights to like round plates, others will have their own ideas too...
Since You mentioned it and it is of interest to me - i have every DS from Frank's pages - GE and one RCA datasheet show grid current almost up to the maximum working conditons, graph Average Plate Characteristic - as a more experienced builder what is Your opinion on this and application in class A as possible phase inverter ( mentioned in GE DS i think ) ?
P.S. Where two datasheets actually show classic looking triode curves, Class A methinks ( Tung-sol ) there is no mention or showing off grid current.
That is not the topic, I use and like a variety of tubes as well. The actual topic was to see if there are other people having the same opinion as Andy. Looks like we are 4 people until now (me, Andy, Thomas and directdriver). While other tubes with different gemometry might be better, that good or not that good, round plate tubes all seem to share the same "properties" and be quite close to each other.
Most of the posts are instead from people with no idea about it. As I said in my first post it also has to do with michrophonics. You must try it for real to know. Now that you have some actual curves of a round plate tube, you can't just dismiss it with a generic comment.
I can replay to your post just saying that actually, if IDHT triodes can be so good, DHT's could be even better. So?
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@krca45 of course you can use it as phase splitter but not with grid current. The curves in the datasheet are simply not good enough, lacking resolution on the vertical axis (i.e. it shows the curves for each triode up to 15-20 mA when in reality you are going to run it at about 3-3.5 mA). For that reason and because they are average curves, they do not look appealing. But in reality it is better.
The curves with positive grid bias are meant to be used for PP class B2 amp (i.e. ouput power stage with 0V bias) for 10W ouput! But it's not really HiFi...
The curves with positive grid bias are meant to be used for PP class B2 amp (i.e. ouput power stage with 0V bias) for 10W ouput! But it's not really HiFi...
why do i have to do that? i am not arguing with you....
tubes have plate/transfer curves, what is the deal with that...? what does it prove anything about round plates?
the 6en6/6w6 tubes have rectangular plates, they sound fantastic in my amps, the 6v6 have oval plates, EL84 have semi oval pates, but i like it anyway....the 6gk6 have round plates, i like them too...
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I said that with round plates you get consistent results within the family. With other geometries you can only pick up specific examples.
That is the topic. I don't care if specific tubes are better. I know that, you don't need to tell me that. I have been using the 45, PCL/ECL82 and EL84 together with the 6F6 for over 25 years...
That is the topic. I don't care if specific tubes are better. I know that, you don't need to tell me that. I have been using the 45, PCL/ECL82 and EL84 together with the 6F6 for over 25 years...
any tube that have depleted cathodes and lost transconductance as a result will never sound good, they have reached the end of their life, round plates or not...
tubes datasheets did not even mention plate construction, unless you see actual samples, and they vary from manufacturer to manufacturer, some larger plates than the others even of the same types...
you can not possibly see all of them in your lifetime to even have an opinion...
unsolicited advice, i learned 95% of what i know about tubes from this forum, but when i started here in 2003, i was never concerned about how tubes looked, and i was very eager to learn how tubes worked, and this is just about the best place there is to learn tubes, where posters are eager to fill you in with good information, so my advice is to look beyond how any tube looked, instead learn how they work....
i believe that i learned how to pick the grains from the chaff, that is not so hard if you are disciplined enough....
tubes datasheets did not even mention plate construction, unless you see actual samples, and they vary from manufacturer to manufacturer, some larger plates than the others even of the same types...
you can not possibly see all of them in your lifetime to even have an opinion...
unsolicited advice, i learned 95% of what i know about tubes from this forum, but when i started here in 2003, i was never concerned about how tubes looked, and i was very eager to learn how tubes worked, and this is just about the best place there is to learn tubes, where posters are eager to fill you in with good information, so my advice is to look beyond how any tube looked, instead learn how they work....
i believe that i learned how to pick the grains from the chaff, that is not so hard if you are disciplined enough....
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What defective tubes and end-of-life have to do with this discussion?
Datasheets do not mention it and often the very same tube comes in different constructions but that was often some necessity of the moment or done to avoid copyrights (?). In the former case, they simply stuck in the bulb what they had available like, for example, an oval plate for the 6F6 instead of a cylidrical one. Well I have both, tried both and the oval type is not quite at the same level.
Manufacturers' practices of this kind had to do more with production, saving money etc...that doesn't change the fact a certain tube was originally designed in certain way.
Datasheets do not mention it and often the very same tube comes in different constructions but that was often some necessity of the moment or done to avoid copyrights (?). In the former case, they simply stuck in the bulb what they had available like, for example, an oval plate for the 6F6 instead of a cylidrical one. Well I have both, tried both and the oval type is not quite at the same level.
Manufacturers' practices of this kind had to do more with production, saving money etc...that doesn't change the fact a certain tube was originally designed in certain way.
I picked up 25 NOS in boxes 6C5 (Hytron) tubes a while back, pristine, even the boxes look like new. 6C5 is the predecessor to 6J5, it is very cylindrical, looks like a church bell hanging over the rather beefy cathode post. It has extra mica supporting the cylinder. I haven't tried them yet but I would think a cylindrical bell-like plate might be more prone to pick up vibration.
The late Dave Kimber, aka DF96, used to have an article on this topic in his website, which understandably disappeared. He pointed out the reasons for the technical advantage of cylindrical plate tubes. For those who know DF96, he was as technical and no-BS as you can get. Unfortunately I can't recall all the details and the website is gone. I'm not smart enough to defend cylindrical plate tubes' superiority in the SAME TUBE TYPE or family, eg, 6SN7 vs 6J5, and I can only go by my subjective observations. There are certainly fine sounding tubes with other plate shapes and I didn't mean to stir things up. I would like to read more about how plate geometry affects performance from a technical standpoint. I will go back to lurking now.
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I agree - I asked an open question because I was curious. I actually didn't say "all cylindrical plates sound better than all non-cylindrical plates" but several people jumped on the subject in a knee-jerk way and took it to mean that. That's not what I said. In the original post I said this:
"I also use 27, 37, 56, 76 as small signal tubes so no argument there. But I can think of many superb tubes like 10Y with flat anodes."
So even in the original post I said "not necessarily so". So there.....
Having said that, I have used a sufficiently large numbers of tubes that I really like with round anodes to see a possible trend, hence the thread. Plus I take Thomas Mayer very seriously as a tube expert and designer so his opinion added weight. But it still remains an open question, and not an easy one to answer. But the most valuable posts here are the ones that actually refer to the geometry and construction of tubes and the question of whether it's possible to construct perfectly symmetrical geometry. TM says yes and proved it by actually making the tubes. He walked the walk, rather than just talk the talk. We may have to wait a while for anyone to come up with curves and measurements for his new tubes, but I guess some owner will eventually put one on a curve tracer.
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