Under the getter of a valve like the EL34 there are two plates attached to the supports for the control grid, the two sides of each being bent backwards away from the other plate.
Are these there to control grid capacitance, keep the grid cool, some of both or something else? Like something to do with the getter firing process.
I've had a look around on the net and haven't been able to find any mention of what these are there for.
Are these there to control grid capacitance, keep the grid cool, some of both or something else? Like something to do with the getter firing process.
I've had a look around on the net and haven't been able to find any mention of what these are there for.
An externally hosted image should be here but it was not working when we last tested it.
Just a wee bit more on those fins. . . .
Folks may have by now picked up that I am fond of using 6L6GCs, but I found quite a variation in construction especially in products from the East. Checking the G1 cooling fins is important (if one is in the position to do so) to determine what exactly you have - it can make the difference between a 25W and 30W plate dissipation. I have found those on the NOS GE 6L6GC models quite larger than on similar annotated Russian tubes. Also, the mounting pins are thicker on the former . . . all contributing to extra heat conduction. One could assist heat dissipation still further by using octal sockets with wrap-around as opposed to fork type connectors, with extra cooling fins on the socket (keeping in mind safety and capacitance). Heat sinks are not only for transistors!
Folks may have by now picked up that I am fond of using 6L6GCs, but I found quite a variation in construction especially in products from the East. Checking the G1 cooling fins is important (if one is in the position to do so) to determine what exactly you have - it can make the difference between a 25W and 30W plate dissipation. I have found those on the NOS GE 6L6GC models quite larger than on similar annotated Russian tubes. Also, the mounting pins are thicker on the former . . . all contributing to extra heat conduction. One could assist heat dissipation still further by using octal sockets with wrap-around as opposed to fork type connectors, with extra cooling fins on the socket (keeping in mind safety and capacitance). Heat sinks are not only for transistors!
Names and labels!
Is it me, Or, is there a Humongous amount of 'Label Snobbery' in the realms of tube-audio, and maybe audio in general??
Two tubes, One make A, other make B, Both same type, and test the same.
DO they REALLY sound THAT much different, in a well designed amp??-
-I bet Blind-Testing would show some interesting results!
Granted, different TYPES of tube may 'colour' the sound in their own way, as well as different topology will too, but different makes of the same type? and is it worth spending out the mega-bucks some guys do??
Recently I had a pair of NOS Osram KT66, from the 1940's, Taper ST types, smoked glass, perfect condition. Tested these out in a Quad II, against some Russian tubes made a year ago. I honestly couldnt tell any difference at all in the sound.
I sold the Osrams for 200 pounds sterling, and plan to use the cash for up and coming projects, using more affordable tubes!
SY said:
Is it me, Or, is there a Humongous amount of 'Label Snobbery' in the realms of tube-audio, and maybe audio in general??
Two tubes, One make A, other make B, Both same type, and test the same.
DO they REALLY sound THAT much different, in a well designed amp??-
-I bet Blind-Testing would show some interesting results!
Granted, different TYPES of tube may 'colour' the sound in their own way, as well as different topology will too, but different makes of the same type? and is it worth spending out the mega-bucks some guys do??
Recently I had a pair of NOS Osram KT66, from the 1940's, Taper ST types, smoked glass, perfect condition. Tested these out in a Quad II, against some Russian tubes made a year ago. I honestly couldnt tell any difference at all in the sound.
I sold the Osrams for 200 pounds sterling, and plan to use the cash for up and coming projects, using more affordable tubes!
*Puts on Flamesuit*
I've actually heard a difference between the *same type* of rectifier tube in my small PP6V6 amplifier.
5U4G and 5U4GB...I prefer the "punch" of the GB. (the 5U4G's seem a bit "softer",IME.)
Now,I'm not sure of the cause of the different sound,I'm *assuming* it has to do with the differing voltage drops of the two tubes,internal impedance,etc.
I havn't usually noticed much difference bewteen say 2 5U4's or 2 12AX7's that are the same brand,unless one was weak,and worn.
I can hear differences between different brands of (say) 12AX7's though. (I kinda like the Sovtek 12AX7LPS,and Bugle Boys..Not so fond of Mullard and Tele myself,atleast in this amp.)
I've actually heard a difference between the *same type* of rectifier tube in my small PP6V6 amplifier.
5U4G and 5U4GB...I prefer the "punch" of the GB. (the 5U4G's seem a bit "softer",IME.)
Now,I'm not sure of the cause of the different sound,I'm *assuming* it has to do with the differing voltage drops of the two tubes,internal impedance,etc.
I havn't usually noticed much difference bewteen say 2 5U4's or 2 12AX7's that are the same brand,unless one was weak,and worn.
I can hear differences between different brands of (say) 12AX7's though. (I kinda like the Sovtek 12AX7LPS,and Bugle Boys..Not so fond of Mullard and Tele myself,atleast in this amp.)
Why I don't leave well alone as my grandmother taught me.......
I would agree with AlastairE (there; now they must shoot 2 of us).
But as my conscience (read scientific background) buggs me, I have found honest day-practical folks insisting that they hear differences. Some have been sorted out by blind tests. In other cases I found measured differences between tubes, that should not exist - but there. Would anybody expect to find a difference of 26% between 2 halves of a double triode (a "special" tube)?
I did.
Concerning rectifiers there can be an audible difference between directly and indirectly heated tubes (like the 5U4 and 5V4). The latter has a lower internal resistance and will therefore cause a higher peak charging current. These differences are small, but if this manifests as a difference in noise, it might be experienced as "better sound". That is as far as I am prepared to go. But the mind is very subtle and capable of influence. What is subjectively interpreted is often not what has changed exactly.
I would agree with AlastairE (there; now they must shoot 2 of us).
But as my conscience (read scientific background) buggs me, I have found honest day-practical folks insisting that they hear differences. Some have been sorted out by blind tests. In other cases I found measured differences between tubes, that should not exist - but there. Would anybody expect to find a difference of 26% between 2 halves of a double triode (a "special" tube)?
I did.
Concerning rectifiers there can be an audible difference between directly and indirectly heated tubes (like the 5U4 and 5V4). The latter has a lower internal resistance and will therefore cause a higher peak charging current. These differences are small, but if this manifests as a difference in noise, it might be experienced as "better sound". That is as far as I am prepared to go. But the mind is very subtle and capable of influence. What is subjectively interpreted is often not what has changed exactly.
I believe there is a lot of truth (and hype) to both sides of this argument. First of all, I have no experience with and of the high dollar "audio snob" type tubes. I don't have the funds to purchase any of these. I do own 3 vintage RCA 845's, and I got them for free! I have a warehouse containing over 100,000 tubes,which I got in exchange for a few days work. I have been in the process of testing the ones that I have hundreds of to find ones that are suitable for audio. I have come to a few conclusions.
There is a wide variation in the performance of tubes of the same type, from the same manufacturer. There is a wider variation between tubes of different manufacturers. The "sweet spot" (point of optimum performance) may be different from one manufacturer to another. If a circuit is optimized for a tube of one manufacturer, it may work better with that tube, than with the same tube from a different manufacturer. Given the fact that many audiophiles have similar amplifiers, it is no surprise that there are audible differences between different manufacturers tubes.
I have purchased several " new production" tubes from Russia and China, and found that some of them are excellent, and some of them are horrible, with most in between. The variation from tube to tube is much greater.
With that being said, I can hear very little difference between the $28USD Shuguang (China) 845, and my original RCA 845's. I guess people will be calling me deaf! I doubt if I could pick out the RCA's in a blind test. However I can hear a world of difference between the Sovtek 300B's and the Shuguang 300B's. But which one sounds better? That depends on the amp. The 300Beast (push pull) likes the Sovteks, and all of the SE amps that I have built definitely sound better with Shuguangs. Unfortunately, the Sovteks have poor reliability.
As far as "Audio Snobery" is concerned, where else would there be a market for 200 dollar power cords, 500 dollar speaker wire, and 150 dollar "magic stones" that clarify the sound by absorbing stray magnetic fields. You need one for every transformer in your amp. Viral marketing is alive and well!
There is a wide variation in the performance of tubes of the same type, from the same manufacturer. There is a wider variation between tubes of different manufacturers. The "sweet spot" (point of optimum performance) may be different from one manufacturer to another. If a circuit is optimized for a tube of one manufacturer, it may work better with that tube, than with the same tube from a different manufacturer. Given the fact that many audiophiles have similar amplifiers, it is no surprise that there are audible differences between different manufacturers tubes.
I have purchased several " new production" tubes from Russia and China, and found that some of them are excellent, and some of them are horrible, with most in between. The variation from tube to tube is much greater.
With that being said, I can hear very little difference between the $28USD Shuguang (China) 845, and my original RCA 845's. I guess people will be calling me deaf! I doubt if I could pick out the RCA's in a blind test. However I can hear a world of difference between the Sovtek 300B's and the Shuguang 300B's. But which one sounds better? That depends on the amp. The 300Beast (push pull) likes the Sovteks, and all of the SE amps that I have built definitely sound better with Shuguangs. Unfortunately, the Sovteks have poor reliability.
As far as "Audio Snobery" is concerned, where else would there be a market for 200 dollar power cords, 500 dollar speaker wire, and 150 dollar "magic stones" that clarify the sound by absorbing stray magnetic fields. You need one for every transformer in your amp. Viral marketing is alive and well!
tubelab.com said:
200 dollars for a power cord?
I see you're still at the budget end of the market. What I like about the cables is the way guys will be spending thousands on the wires that they could have just missed out by connecting the two parts together in one box to start with. Instead they end up buying cables that cost as much as what's in the boxes.
However, I believe I have actually found something to contend with the audio market's trend for setting so far unexplainably gigantic prices for individual bits of a system. And it is...
QVC's cosmetics shows
Molton Brown Bubble Bath - 49.99 UK
'Build you a new face to get you more action' skin cream - 79.99 UK
I am encouraged to find others with their engineering in order. I thought I was "a lonely little engineer in a subjectivist patch" (apology to Patti Page, I think). I write for a local audio magazine, where many readers sincerely think I should return my school money for daring to suggest that hearing might be subjective.
But I do have the edge on the cable afficionados. They still have to discover that, with all that frenzied electron traffic in cables, these things wear out! That is why you really have to replace after 2 years!
Friend Tubelab, I find I cannot contact you directly. I wondered if among your stock you may have a few original GE 6L6GCs left. Main purpose being to install tubes of the same appearance as ones I am already using. If so please contact me directly (e-mail through my logo). I will appreciate.
But I do have the edge on the cable afficionados. They still have to discover that, with all that frenzied electron traffic in cables, these things wear out! That is why you really have to replace after 2 years!
Friend Tubelab, I find I cannot contact you directly. I wondered if among your stock you may have a few original GE 6L6GCs left. Main purpose being to install tubes of the same appearance as ones I am already using. If so please contact me directly (e-mail through my logo). I will appreciate.
I am an engineer in the high tech industry. I work in a building where there are over 1000 engineers (electrical, mechanical, and software). I have found two people here who are verified Tubeheads. Most of the engineers here have never heard of vacuum tubes, and the ones who have would not dream of using one.
Although I have over 100,000 tubes, the reason that these were given to me is that they had already been picked over (more than once) and all of the common audio tubes had been removed. So far I have sorted through most all of the tubes. I have found about 5 6L6 types, and none of them were GC's, and only two were any good.
I am trying to find tubes that I have lots of, that will work well for audio. In the process, I am trying to use sound engineering principles to solve the issues that I find. That is how PowerDrive was born. Unfortunately there is very little engineering being done in the vacuum tube world. The void is often filled up with hype for the latest "new" circuit, or gadget that can be cleverly marketed.
Although I have over 100,000 tubes, the reason that these were given to me is that they had already been picked over (more than once) and all of the common audio tubes had been removed. So far I have sorted through most all of the tubes. I have found about 5 6L6 types, and none of them were GC's, and only two were any good.
I am trying to find tubes that I have lots of, that will work well for audio. In the process, I am trying to use sound engineering principles to solve the issues that I find. That is how PowerDrive was born. Unfortunately there is very little engineering being done in the vacuum tube world. The void is often filled up with hype for the latest "new" circuit, or gadget that can be cleverly marketed.
Ok back to the question about the "fins" on top...
Heat sinks? Coolers? On top?????????
Sure, put them where all the heat is.
Seems more like a form of stray field control thingy. You know, like the suppressor grid. Probably keeps the blue glow at bay.
I think the RCA tube manual actually has a description of those thingys near the beginning, where they have an exploided view of the tube and describe all the innards. I will have to look this evening.
Later!
Gabe
Heat sinks? Coolers? On top?????????
Sure, put them where all the heat is.
Seems more like a form of stray field control thingy. You know, like the suppressor grid. Probably keeps the blue glow at bay.
I think the RCA tube manual actually has a description of those thingys near the beginning, where they have an exploided view of the tube and describe all the innards. I will have to look this evening.
Later!
Gabe
The fins ARE actually heat radiators. The grid wires absorb heat, so do the posts that they are wound on. If the control grid gets too hot, it will start emitting electrons, which is otherwise known as grid current. This will lower the effective grid bias, causing the tube to draw more current, and get hotter. This can cause a runaway condition, leading to a red glow, a hum in the speaker, and a very unhappy output tube. This is also why there is a maximum grid circuit resistance spec. That grid current needs a place to go.
If you think about it, where else are you going to put the heat radiator? It must be attached to the control grid (and sometimes the screen grid). On some tubes, the 6AS7 comes to mind, this radiator is large and elaborate. There may also be one on the bottom of the tube. The 6AS7 design is also prone to grid current problems.
If you think about it, where else are you going to put the heat radiator? It must be attached to the control grid (and sometimes the screen grid). On some tubes, the 6AS7 comes to mind, this radiator is large and elaborate. There may also be one on the bottom of the tube. The 6AS7 design is also prone to grid current problems.
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