[EdipisReks]

just in case anyone was interested, this is a 7N7 being used as the gain tube in my 6CG7 PPX3 Slam

yes, that is a pair of adapters (neither adapter is a Singlepower, they predate Mikhail's adapter line). that's a National Union branded tall bottle 7N7 with a pair of Tung-Sol D getter 5687s. i'll be getting that 9 pin socket switched out for a regular ol' octal socket eventually (probably when i get a new transformer and maybe a stepped attenuator installed), but i thought that people might be interested in seeing how this particular combo looks. it works perfectly fine and sounds very nice.

 

[sacd lover]

I always called this pairing the "totem pole".

 

[EdipisReks]

it's a very fitting name

 

[luvdunhill]

lots of "yang" there man...

 

[augustwest]

How do you like the National Union tall grey glass tube?

I got a couple last Friday. They are labled "Tung Sol", but most likely made by National Union. After listening to them for a bit I found that I liked the "short bottle" black plate better. I'm really liking the 7n7, and place it right up there with my favorite 6sn7 tube, and in some instances prefer the 7n7.

I'm now anxious to try the 12ax7 family of tubes, once I get an adapter.


- augustwest

 

[sacd lover]

Quote:

Originally Posted by augustwest How do you like the National Union tall grey glass tube? I got a couple last Friday. They are labled "Tung Sol", but most likely made by National Union. After listening to them for a bit I found that I liked the "short bottle" black plate better. I'm really liking the 7n7, and place it right up there with my favorite 6sn7 tube, and in some instances prefer the 7n7. I'm now anxious to try the 12ax7 family of tubes, once I get an adapter. - augustwest

The 12ax7 and 12at7 have to much gain

.... stick with the 12au7/5814a.

The 7N7 Reks is showing is not a NU. Thats an unknown production year sylvania. I broke open an identical non-functioning tube and the tube has the standard sylvania tall bottle construction. The true NU 7n7's will have a break in the gray glass coating at the bottom of the tube and you can see the round plate construction.

 

[EdipisReks]

this particular tube sounds as good as the regular (non bad boy) bottom getter Sylvania 6SN7GT. it's a nice tube.

 

[sacd lover]

Quote:

Originally Posted by EdipisReks this particular tube sounds as good as the regular (non bad boy) bottom getter Sylvania 6SN7GT. it's a nice tube.

It looks like the same tall bottle 6sn7gt construction inside. You dont see many of these and they never have any date codes etc ... so I cant figure out when they were made.

 

[augustwest]

"The 12ax7 and 12at7 have to much gain"

So I imagine that the 5751 would be a good candidate to try too, since it has less gain than the 12ax7. Is that correct?

"The true NU 7n7's will have a break in the gray glass coating at the bottom of the tube and you can see the round plate construction."

I will check mine when I get home, my recollection is that, it does have about a quarter inch gap in the grey graphite coating.

- augustwest

 

[sacd lover]

Quote:

Originally Posted by augustwest "The 12ax7 and 12at7 have to much gain" So I imagine that the 5751 would be a good candidate to try too, since it has less gain than the 12ax7. Is that correct? "The true NU 7n7's will have a break in the gray glass coating at the bottom of the tube and you can see the round plate construction." I will check mine when I get home, my recollection is that, it does have about a quarter inch gap in the grey graphite coating. - augustwest

The 5751 is a sometimes substitute for the 12ax7 in guitar amps .... and is a very high gain tube. The SP amps typically use gain tubes with an amplification factor between 15-20 .... like the 6cg7/ 6sn7/ 7af7 /7n7. The other tubes used sporadically for gain like the 5687 have an amplification factor of 17 ..... the 6bl7gt is 15 and the 6bx7gt is only 10.

The 12 series has the folowing amplification factor specs ....

12ax7 = 100, 5751 = 70, 12at7 =60, 12au7/5814a = 17.

Thats why I recommended the 12au7.

 

[augustwest]

"The 5751 is a sometimes substitute for the 12ax7 in guitar amps .... and is a very high gain tube. The SP amps typically use gain tubes with an amplification factor between 15-20 .... like the 6cg7/ 6sn7/ 7af7 /7n7. The other tubes used sporadically for gain like the 5687 have an amplification factor of 17 ..... the 6bl7gt is 15 and the 6bx7gt is only 10.

The 12 series has the folowing amplification factor specs ....

12ax7 = 100, 5751 = 70, 12at7 =60, 12au7/5814a = 17.

Thats why I recommended the 12au7."

Thanks for explaining. I can see that the; 12ax7 = 100, 5751 = 70, 12at7 =60; are way too high in terms of amplification for use in the SP amps.

- augustwest

 

[jamato8]

The 12FQ7 can replace the 12AU7 in many circuits and has the same type of demands as the 6SN7 but of course it has a 12 volt filament. It lasts a long time can sound very good when you get a good version and is around 5 or 6 dollars.