[L0rdGwyn]

The NU 6N7GT/T is a great sounding tube - the gray glass are from the 40's.
I have been able to fix some noisy tubes (pops and crackles - not hum) by heating each tube pin with a 30W soldering iron for around 30 seconds. Just hold the tube upright so that any solder that might flow doesn't end up inside the tube.
For hum and microphonics I have had luck by applying and stretching a tight band of self fusing silicone tape around the glass.
Question: When you measure a quad temperature, are you referring to the tubes themselves (hottest point) or the amp chassis? I would think that what counts is the amp temperature.
IMHO I have also noticed that tubes that have been burnt in and used for a longer time tend to run less hot compared to when new.
PS: It seems to me that that NU is gray glass (haven't seen any black glass 6N7GT) but who knows.....

@mordy you gave me your 30 second soldering iron tip a while back, finally got around to giving it a try. I have a beautiful Fivre 6N7G that tests perfectly in my tester, but is plagued by noise. Using your method took the noise from a 10 down to a 1, and I suspect a second go-around might take it to a 0, I am in your debt! This is a special tube for me and I was very distraught at how unusable it was. I will try this on the EL32 next, they have given me a lot of trouble.

Here it is with a pair of Western Electric 421A. Listening to Aphex Twin - Selected Ambient Works Volume II

 

[UntilThen]

I learned allot about designing SS amps Don't use that much anymore I think tubes have better SQ.

The eternal debate. Similar to vinyl vs digital. One thing I'm sure. I prefer tube amps for headphones. For speakers, I've heard very good ss amps. Such as the Gryphon Antileon EVO at Audio Connections, to a lessor extent the Luxman L-509X and also my Sansui AU-Alpha 907MR.

 

[mordy]

Hi LG,
Thanks for your kind words - I have managed to salvage several tubes this way. Wonder how many tubes have been discarded that could have been made usable again......
Hypnos1 took this method one step higher. He had a rare EL39 tube that was unusable because of loud pops and crackling. After applying heat for 30 seconds, the tube returned to being usable again, but then started up again.
He somehow figured out which pin was giving trouble, and cut off a little piece of the tip. Then he wedged in a piece of copper wire and filled up the inside of the pin with more solder. Voila! The tube works perfectly now!

Now I have to learn the method how to whack a tube to make disjointed wires inside come together to make it usable again! Haven't tried it yet, but I have one or two 6336 tubes that light up but don't function.

Re the EL32, I have a pair that sounded terrible with 6X6BX7 with terrible and scary pops and noises - stopped using them. In this case I think that there is an incompatibility with the BX/BL tubes because JV reported that using other power tubes such as the 6H13C he did not have any problems. Have no idea why they don't work with the BX tubes.

 

[mordy]

Here is a question:
Somebody said that the Tung Sol 5998 clear top is a rebranded Western Electric 421A - is this true?

 

[L0rdGwyn]

Hi LG,
Thanks for your kind words - I have managed to salvage several tubes this way. Wonder how many tubes have been discarded that could have been made usable again......
Hypnos1 took this method one step higher. He had a rare EL39 tube that was unusable because of loud pops and crackling. After applying heat for 30 seconds, the tube returned to being usable again, but then started up again.
He somehow figured out which pin was giving trouble, and cut off a little piece of the tip. Then he wedged in a piece of copper wire and filled up the inside of the pin with more solder. Voila! The tube works perfectly now!

Now I have to learn the method how to whack a tube to make disjointed wires inside come together to make it usable again! Haven't tried it yet, but I have one or two 6336 tubes that light up but don't function.

Re the EL32, I have a pair that sounded terrible with 6X6BX7 with terrible and scary pops and noises - stopped using them. In this case I think that there is an incompatibility with the BX/BL tubes because JV reported that using other power tubes such as the 6H13C he did not have any problems. Have no idea why they don't work with the BX tubes.

I will keep that in mind, I'd imagine being able to resolder or rebase tubes would be useful skill, I know it can be done.

And that has been my experience too with the EL32, pops, sizzles, and clicks. Too bad as they are nice tubes, I think the gain of the 6BX7 plays a part. I am going to try the solder method on them, nothing to lose at this point.

 

[UntilThen]

Re the EL32, I have a pair that sounded terrible with 6X6BX7 with terrible and scary pops and noises - stopped using them. In this case I think that there is an incompatibility with the BX/BL tubes because JV reported that using other power tubes such as the 6H13C he did not have any problems. Have no idea why they don't work with the BX tubes.

I have absolutely no problems with my Mullard EL32 grey glass with 6 x 6bx7gt. In fact, one of my quieter combinations.

 

[L0rdGwyn]

Here is a question:
Somebody said that the Tung Sol 5998 clear top is a rebranded Western Electric 421A - is this true?

That is yet another debate, are they different tubes? Most say the 421A is a TS rebrand. My personal experience is they sound similar but noticably different. The clear top 5998 is very uncommon though, so hard to compare.

I have found the 5998 with the copper rods sounds closer to the 421A than the non-copper rod 5998.

If the 421A is truly just a 5998, does that mean TS also manufactured the 422A? That has always confounded the argument for me. I suppose that would mean WE sourced the components from TS or contracted to have them manufactured, since there is no TS equivalent.

 

[mordy]

I have absolutely no problems with my Mullard EL32 grey glass with 6 x 6bx7gt. In fact, one of my quieter combinations.

Are your Mullard EL32 ST type? I have the inexpensive straight glass ones.

 

[mordy]

I will keep that in mind, I'd imagine being able to resolder or rebase tubes would be useful skill, I know it can be done.

And that has been my experience too with the EL32, pops, sizzles, and clicks. Too bad as they are nice tubes, I think the gain of the 6BX7 plays a part. I am going to try the solder method on them, nothing to lose at this point.

H1 has managed to rebase tubes, but it is a very delicate and difficult task fraught with failures.....
It would be great to put on octal base on a side contact tube like the EL3N, but I assume that it is too difficult a task for most people.

 

[UntilThen]

Are your Mullard EL32 ST type? I have the inexpensive straight glass ones.

I've all the EL32 / CV1052 types. 4 x ST clear glass, 2 x grey glass (these ones from the India seller where the tubes are immaculate) and the 2 x straight ones from Langrex.

ALL of these are quiet with 6 x 6bx7gt or 6BL7gt. They sound very good and are very quiet. Just lower gain but ain't too bad. Just need to increase volume and all will be well.

 

[mordy]

I have the same type as those on the right - there is a possibility that the Chinese made adapters are the culprit.

 

[UntilThen]

I have the same type as those on the right - there is a possibility that the Chinese made adapters are the culprit.

Possibly. I have the chinese made adapters too but I've stopped using them because there's no key guide and you better slot it in right.

 

[UntilThen]

When my GOTL had problems, I thought it was the EL32 tubes but Glenn diagnosed it as a burn out resistor. After he replaced that, I've no more problems.

 

[UntilThen]

Right now the EL32 straight ones are in with 6 x GE 6bx7gt. There is ZERO noise. I can't believe it. Sounds damm good too for 4 pounds a tube from Langrex. Volume at 12 noon is LOUD.

https://www.ebay.com.au/itm/EL32-CV...224426?hash=item3cb6d18dea:g:JFQAAOSw7Kldep3F

 

[myphone]

That is yet another debate, are they different tubes? Most say the 421A is a TS rebrand. My personal experience is they sound similar but noticably different. The clear top 5998 is very uncommon though, so hard to compare.

I have found the 5998 with the copper rods sounds closer to the 421A than the non-copper rod 5998.

If the 421A is truly just a 5998, does that mean TS also manufactured the 422A? That has always confounded the argument for me. I suppose that would mean WE sourced the components from TS or contracted to have them manufactured, since there is no TS equivalent.

I don't have GOTL. I have many TS 5998 including several clear top (1950 - 1960's) and WE 421a (1950, 1960, 1970, and 1980's) Clear top 5998 structurally is similar to same period WE 421a (smaller tail wire than 421), and sounds similar to 421a (a bit less bloom and stage) used in OTL amp. They are quite different from regular 5998.