[r one]

  Very interesting answer Badas. Tomorrow, i'll test the second NU (i've bought a pair). Perhaps Balancing Act is one of this amp which make some noise with this NU 6F8G . I've got TS 6F8Gs round and flate plate and they're totally quiet.
I'll tell you results tomorrow. Thanks for your advertise Badas

Finally i sent back to the seller my pair of NU 6F8G. it's a shame, the sound seemed very good, sweety and delicate. So i've picked up, for exchange, beautiful NOS Ken Rad earlier 6SN7 black glass version.

 

[Oskari]

  Currently on eBay, listing #311134071038, there is a Tungsram 6F8G. Is this likely a rebrand? Or do we know that Tungsram made these tubes?

 
I don't find it implausible. We know that British Tungsram made 6SN7GTs. Tungsram quite possibly made them in Hungary as well (http://www.head-fi.org/t/479031/6sn7-tube-addicts/1335#post_7861603). So, why not 6F8Gs?
 
On the other hand, relabels are entirely possible, too. Tungsram had operations in quite a few countries.
 
I wish there were more photos; I almost feel like buying it to take a closer look.

 

[Mechans1]

  Finally i sent back to the seller my pair of NU 6F8G. it's a shame, the sound seemed very good, sweety and delicate. So i've picked up, for exchange, beautiful NOS Ken Rad earlier 6SN7 black glass version.

I think you'll enjoy the Ken Rads, they have the fullest and deepest bass I have heard a 6SN7 influence in my systems over the years.  The black glass looks nice in many applications if that matters.

 

[MIKELAP]

                                                        

 

[r one]

 
I think you'll enjoy the Ken Rads, they have the fullest and deepest bass I have heard a 6SN7 influence in my systems over the years.  The black glass looks nice in many applications if that matters.

I hope too.

 
Actually my favorite drive tube for deepest bass is 6F8G tung sol flate plate with square mica on top. I've tried RCA, bass is powerful but not very defined.
 
@ Mikelap : really gorgeous pic !

 

[Mechans1]

The Ken Rad is not the tube I am using at the moment myself, which is a Brimar CV1988 6SN7GTY.  I have way too many 6SN7s, (a lot), to start collecting another tube as seductive as the 6F8G sounds.  If I would buy or trade for another tube it would be a really primo 5998 type , which is my amps output tube.  Bought some really tired 421As disappointing, using Tung Sol 5998s which are  very, very good.

 

[Khragon]

I'm listening to two NU6F8G's in my Woo WA22 as I type this in. They were NOS last week and I heard no noise right from the first minute.

Tony and I have discovered a issue with the NU and at the moment working on why. Work in progress. At this early stage it seems that the NU6F8G only works in some circuits.

We have discovered that the NU works absolutely beautifully in the WA6 and WA22. In the WA5 it produced noise. The thinking at the moment is amps with less power entering the 6SN7 circuit are fine. Others that have more power from like a 300B power tube creates noise.

With this new info the NU6F8G comes with a cautious warning. Be aware it may not work in some amps.

A real pity as it is a beautiful sounding tube.

Too late! got NU 6F8G and turns out noisy on my WA5.. so I confirmed the finding that NU 6F8Gs are noisy on the WA5.. too bad ...

 

[TonyNewman]

 
Too late! got NU 6F8G and turns out noisy on my WA5.. so I confirmed the finding that NU 6F8Gs are noisy on the WA5.. too bad ...

 
Yep - it's a total nuttbuster as the NU is a gorgeous sounding tube. Lovely, rich SQ from the WA6 with the Brimar rectifier, but crackle and screech in the WA5

 

[r one]

Yep, i'm disappointed too. These tubes seems to be gorgeous for my ears.

 

[Khragon]

Maybe I'll send them to Woo to see if they can do anything about it, I have no other amp to use them on now anyhow.

 

[sasquatch98]

Does anyone have a preferred method for repairing cracks in Bakelite bases? I found a good price on a sylvania 6sn7gt that test nos but has a small crack in the base. I was going to either put some super glue or JB Weld over the crack to keep it from expanding, anything that would work better?

 

[GrindingThud]

Clear fingernail polish

 

[lojay]

Is there a difference in sound between the B65 brown base and B65 metal base? 
 
My preferences are towards a more solid state, detailed and airy sound, preferably to be able to dissect complex classical passages with ease. 

Other 6SN7 recommendations are also welcome.

 

[Mechans1]

 
Too late! got NU 6F8G and turns out noisy on my WA5.. so I confirmed the finding that NU 6F8Gs are noisy on the WA5.. too bad ...

Indeed circuits play a critical role in hearing noise ,microphonics, and even the character of  a 6SN7s sound. I had built up a fairly large collection of 6SN7s that I used as a driver tube in a 4o wpc integrated  speaker amp.  Rolling the tubes was really rewarding I could clearly hear the differences between tubes and what made some truly special.  I then bought an AE-3 preamp (by Cary) which used 6SN7s as it's  voltage amplifier.  All of a sudden some of the  tubes which were dead quiet in the other amp,  were very microphonic which is not unusual for the old GTs that were the bulk of my collection.  Fortunately very few had spurious random noises of any other sort.  I side with a well known tube dealer re microphonics, in that unless you tap on your tubes while playing,  and they don't create feedback loops, they are fine.  Nevertheless of course I wasn't thrilled about the microphonia.
The amp I am using now a SinglePower Extreme uses a single 6SN7 in some capacity ,but it doesn't pick up noises of most any type including deliberate tube tapping.  I also find that rolling the tube  has much less impact than rolling had had, in my other gear.  Some amps are built such that tube rolling will have minimal effect such as an ARC pre amp that I once used.  ARC actually told you that you could only make a difference in certain spots.
So yes, circuits matter, big time.

 

[rosgr63]

The circuit a tube is used in is important.
 
Actually my findings are different to yours Mechans1.
I have 3 SP's and I find they respond well to tube rolling.
I use one of them with a pair of Grado SR325is for evaluating my tubes.
One of the SP's is a PPX3-6SN7 which uses 3 6SN7's both as driver and output.
Some noisy 6SN7's drivers became quiet when I use them as outputs.
 
The same can happen, but not always when I use a noisy tube in a different amp.
 
When the operating point changes the tube behaves differently.