[L0rdGwyn]

Are both these tubes graphite tubes?
Are the specs different for a regular 6080 and a graphite one?
The 6528A has an amplification factor of 9 and a transconductance of 37.000 and the 6336B of 2.7/13,500 - is that a similar scenario?

They are not graphite, although I have seen Tung Sol 7802WB out in the wild with graphite plates, probably one of the rarest 6AS7 tubes in existence.

The 6336B vs 6528A is sort of a similar comparison to the 6080 vs 7802 in terms of their relative specs, but I think there are too many variables to use them as a test case in the GOTL and say the same is true for the 7802, but maybe I am wrong!

Edit: one interesting thing I had not considered is the possibility of running four 7802s, with the transconductance of 20,000 a piece at 2.5A heater current, I wonder where that would put the GOTLs output impedance.

 

[whirlwind]

They are not graphite, although I have seen Tung Sol 7802WB out in the wild with graphite plates, probably one of the rarest 6AS7 tubes in existence.

The 6336B vs 6528A is sort of a similar comparison to the 6080 vs 7802 in terms of their relative specs, but I think there are too many variables to use them as a test case in the GOTL and say the same is true for the 7802, but maybe I am wrong!

Edit: one interesting thing I had not considered is the possibility of running four 7802s, with the transconductance of 20,000 a piece at 2.5A heater current, I wonder where that would put the GOTLs output impedance.

Not sure where that would put the output impedance, that would be a question for Glenn, but your transformer would allow you to do this.

 

[L0rdGwyn]

Not sure where that would put the output impedance, that would be a question for Glenn, but your transformer would allow you to do this.

Cool, might be an interesting low-impedance option, I'll have to dig out my Grados!

 

[2359glenn]

Hey Monster, figured I would reply here since it's sort of a GOTL thing. Sorry for the book you are about to read.

Having listened to them both several times, I could give a vague description of the Tung Sol 6080 vs the 7802, but I haven't done an AB. I'm happy to though, I have both, I'll see if I have time today or tomorrow. Right off the bat though, the difference is large when it comes to soundstage, dynamics, resolution.

They do have a very similar internal construction, only difference I see really is a finer grid on the 7802 and some extra support rods. Maybe shinier copper on the 7802 grid rods? I'm splitting hairs HA!



One thing to keep in mind, the only circuit I have ever seen the Tung Sol 7802 used in with listening impressions is a cathode-follower OTL, like the Bottlehead Crack, Woo Audio WA3, etc. In those circuits, the output tube provides near 0 gain no matter its amplification factor, whereas in the GOTL, The 7802 will operate at a gain of 9 and a transconductance of 20,000 and the 6080 at a gain of 2 and a transconductance of 7,000.

From my reading, the higher transconductance of the 7802 vs 6080 in the Crack(atwoa) cathode-follower circuit will have a negligible effect on the output impedance, so I don't think the better sound can be attributed to that, but I'm still not sure if the higher transconductance is contributing in any way to why the tube sounds so good in a cathode follower or if there is another reason. It's hard to say if comparisons are still 1:1 in the BHC vs GOTL.

I'm very curious myself if it will carry over to the GOTL or not, maybe Glenn can help based on the specs, but I won't know for sure until I have the GOTL!!! When I do, this will be one of the first output tubes I try.

I do not recommend using the 7802 in this amp. I tried a pair about 10 years ago they got very hot and didn't sound good. Ran them for about 15 minuets
didn't like the sound and they were screaming hot. They require a 500 ohm cathode resistor and the ones in the amp are 1/2 that so the tubes will be over current
and get very hot and probably ruin them.
They are fine in a cathode follower amp were nothing really matters that much

 

[L0rdGwyn]

I do not recommend using the 7802 in this amp. I tried a pair about 10 years ago they got very hot and didn't sound good. Ran them for about 15 minuets
didn't like the sound and they were screaming hot. They require a 500 ohm cathode resistor and the ones in the amp are 1/2 that so the tubes will be over current
and get very hot and probably ruin them.
They are fine in a cathode follower amp were nothing really matters that much

Well there you go, probably not a good idea then @Monsterzero ! Case closed.

 

[Monsterzero]

Well Schiit!

 

[Zachik]

I do not recommend using the 7802 in this amp. I tried a pair about 10 years ago they got very hot and didn't sound good. Ran them for about 15 minuets
didn't like the sound and they were screaming hot. They require a 500 ohm cathode resistor and the ones in the amp are 1/2 that so the tubes will be over current
and get very hot and probably ruin them.

Updated my compatibility list to reflect this info

 

[gibosi]

I do not recommend using the 7802 in this amp. I tried a pair about 10 years ago they got very hot and didn't sound good. Ran them for about 15 minuets
didn't like the sound and they were screaming hot. They require a 500 ohm cathode resistor and the ones in the amp are 1/2 that so the tubes will be over current
and get very hot and probably ruin them.
They are fine in a cathode follower amp were nothing really matters that much

It's a shame that the 7802 won't work as there are so few output tubes available to use in the GOTL. lol

But for those who enjoy the chase, I would suggest the French-made Thompson CSF 6336A. I have been looking for a pair of these for about 5 years with no luck. I have no idea how they might sound, but again, it's the thrill of the hunt that matters most! Yes?

 

[L0rdGwyn]

The Hateful Eight have all arrived. Fivre must've loved changing up their designs, so much diversity in the build of this tube, finding matched construction in six must be near impossible. Hope the sound is worth the effort it took to put this set together.

 

[whirlwind]

The Hateful Eight have all arrived. Fivre must've loved changing up their designs, so much diversity in the build of this tube, finding matched construction in six must be near impossible. Hope the sound is worth the effort it took to put this set together.

Great job coming up with those.....kudos

 

[mordy]

The Hateful Eight have all arrived. Fivre must've loved changing up their designs, so much diversity in the build of this tube, finding matched construction in six must be near impossible. Hope the sound is worth the effort it took to put this set together.

Hi LG,
Come to think about it, American manufacturers also kept on changing their internal designs. Top getter, bottom getter, side getter, parallel plates, T plates, two micas, three micas, tall tube, short tube, more support rods, less support rods, copper rods, nickel rods, 2 hole plates, 3 hole plates, black plate, gray plate, etc etc.
I guess the difference is that the logos did not change that much compared to the Fivres lol.

 

[L0rdGwyn]

Hi LG,
Come to think about it, American manufacturers also kept on changing their internal designs. Top getter, bottom getter, side getter, parallel plates, T plates, two micas, three micas, tall tube, short tube, more support rods, less support rods, copper rods, nickel rods, 2 hole plates, 3 hole plates, black plate, gray plate, etc etc.
I guess the difference is that the logos did not change that much compared to the Fivres lol.

Oh yes, no doubt, I guess what I should have said was there is more diversity in the build of the Fivre 6BX7 than other brands of 6BX7 I have collected. To be fair, Fivre was manufacturing these tubes much longer than others, since the 40s, while Tung Sol and RCA did not start until the early 60s, for example.

I know most people on this thread probably already have their own way of securing loose tube bases, but I wanted to share a method I've started using that I think is very effective. I have been using Starbond EM-02 cyanoacrylate adhesive, strong stuff. It is water thin, so three or four evenly spaced drops right where the glass meets the base and the adhesive easily seeps and spreads throughout the inside. It is soluble in acetone, so any excess on the glass or base can easily be wiped away with acetone-based nail polish remover. Have to be careful though not to get any on an area of print, as acetone will take it right off. Q-tip is helpful, I sealed up the bases on my two NEC 6AS7Gs very securely, and quickly! I'll report back if any issues come up.

Link: https://www.starbond.com/super-fast-thin-ca-glue.html

 

[mordy]

Oh yes, no doubt, I guess what I should have said was there is more diversity in the build of the Fivre 6BX7 than other brands of 6BX7 I have collected. To be fair, Fivre was manufacturing these tubes much longer than others, since the 40s, while Tung Sol and RCA did not start until the early 60s, for example.

I know most people on this thread probably already have their own method of securing loose tube bases, but I wanted to share a method I've started using that I think is very effective. I have been using Starbond EM-02 cyanoacrylate adhesive, strong stuff. It is water thin, so three or four evenly spaced drops right where the glass meets the base and the adhesive easily seeps and spreads throughout the inside. It is soluble in acetone, so any excess on the glass or base can easily be wiped away with acetone-based nail polish remover. Have to be careful though not to get any on an area of print, as acetone will take it right off. Q-tip is helpful, I sealed up the bases on my two NEC 6AS7Gs very securely, and quickly! I'll report back if any issues come up.

Link: https://www.starbond.com/super-fast-thin-ca-glue.html

I use something similar, but with one more advantage - a little brush in the cap that gets into crevices or in the space where the glass meets the tube base. I also use the brush to apply glue around the anode cap base on old tubes:

Around $3 in Walmart and widely available.

 

[Phantaminum]

Had a little scare yesterday.

We moved to Dallas for a job and have been looking for a house while living in an apartment complex close to work. Apartment building alarm goes off meaning that there could be a possible fire somewhere. The wife and I grab our dogs, wallet/purse, and car keys. Smelled smoke on the way out.

First thing I thought when we were all outside safe, "Damn...the GOTL and tubes are going to be hard to replace if goes up with the building".

Luckily whatever was burned (they were cooking) had been put out by the tenant in that unit.

 

[Monsterzero]

Tonight its Snowy White,Joe Bonamassa,Pink Floyd and The Guess Who.
Who says OTLs and easy to drive headphones dont mix?!
Focal Stellia in the house. Big bass,excellent staging for a closed back,with excellent imaging. Very dynamic.Good stuff.