Quick valve construction question

[eeka chu]

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.

[Alastair E]

They are there, just to remove some heat from the control grid to prevent or control grid-emission.

How come the RUSSIANS are using the old MULLARD logo??

Shurely this is copyright to PHILIPS who owns MULLARD??

[SY]

Lots of old brand names have been licensed out. Tung-Sol, Western Electric... Perfect for the audiophile who believes that sound correlates with brand.

[planet10]

Originally posted by Alastair E
How come the RUSSIANS are using the old MULLARD logo??

New Sensor bought the rights to Mullard & Tung-sol (and probably a few others)

dave

[Johan Potgieter]

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!

[Alastair E]

Originally posted by SY
Lots of old brand names have been licensed out. Tung-Sol, Western Electric... Perfect for the audiophile who believes that sound correlates with brand.

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!

[DigitalJunkie]

*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.)

[Johan Potgieter]

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.

[SY]

Would anybody expect to find a difference of 26% between 2 halves of a double triode (a "special" tube)?

It's unfortunately not uncommon. I especially see large distortion differences with some tubes- the 6BX7 is notorious in this regard, but I've seen some terrible behavior from other tubes, too.

[tubelab.com]

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!