The Reference 6SN7 Thread

[WildPhydeaux]

Well, I should have researched a little more. Not that uncommon apparently. But 5 years ago when I was looking I couldn't find a single reference to the tubes I mentioned in the above post. Meh, old hat around here I guess. Still, they did sound great in my old Cary preamp and in fact they're sounding pretty special in my Lampizator DAC too (paralleled adaptor to 6J5 socket).

Cheers,
Robert

 

[Isaacc7]

@Isaacc7 Your post reminded me that in my previous usage of 6SN6 I had found the 7N7 to be in my own top three tubes in a previous preamp. This was several years ago and I never heard of the Frankie version, but I do have a few tubes that I found notably better than others and I could never find more of them. In fact I couldn't even find anyone who found similar tubes.

They are not Frankie because their bottom mica isn't the oval shape, they are just rounded corner rectangles. I can barely see they are parallel plates but here's where I was confused - they are chrome, flattish tops and grey glass. Some are marked Sylvania and a couple are RCA, but same construction. We know they must be Sylvania because they don't align with NU - who had grey glass ones but not chrome tops.

Any ideas?

Cheers,
Robert

I have a few like that. Not sure if I posted about them here or on other boards. There is just a little bit visible under the grey coating. Could you shine a light and see if you see any support rods, copper or otherwise? I am super curious about the internal construction of these but don’t have the heart to sacrifice a working one just to see its guts.

 

[WildPhydeaux]

Looks to be multiple support rods to the base and at least two copper rods.

Cheers,
Robert

 

[g0ldl10n]

@Isaacc7 Your post reminded me that in my previous usage of 6SN6 I had found the 7N7 to be in my own top three tubes in a previous preamp. This was several years ago and I never heard of the Frankie version, but I do have a few tubes that I found notably better than others and I could never find more of them. In fact I couldn't even find anyone who found similar tubes.

They are not Frankie because their bottom mica isn't the oval shape, they are just rounded corner rectangles. I can barely see they are parallel plates but here's where I was confused - they are chrome, flattish tops and grey glass. Some are marked Sylvania and a couple are RCA, but same construction. We know they must be Sylvania because they don't align with NU - who had grey glass ones but not chrome tops.

Any ideas?

Cheers,
Robert

I have many of these exact 7N7s, as well as a lot of 14N7 of these and agree with you, they sound wonderful and are easily my favorite 7N7/14N7 variant even compared to the more popular "frankie" version, or 14N7 tall bottle version with identical (least I think) internals as the famous Sylvania 6SN7W metal base tubes.

I have a single Sylvania JAN 7N7 with this construction, and then the others are either branded as Sylvania or rebranded GE - I have seen them rebranded as RCA as you noted. Almost certainly all Sylvania but I do believe more than 1 factory made these, because most of mine have the flattish top like the one in your picture, but I have a few with a much more rounded top which I would assume means one of two things, different factory with different tooling/practices the made the glass, or age of manufacturing.

The most interesting thing imo about these specific 7N7/14N7 variant is I don't think there is a 6SN7/12SN7 "twin" with the same internals, flashing and carbonized coating just with octal base, like I believe most, if not all the others have. Maybe I am wrong here though, wouldn't be the first time.

But ya, it's a very lovely tube and glad I have a good stock of them in my collection.


Edit: Here a picture comparing the shape of the glass between the two different types I have.

 

[Isaacc7]

It

I have many of these exact 7N7s, as well as a lot of 14N7 of these and agree with you, they sound wonderful and are easily my favorite 7N7/14N7 variant even compared to the more popular "frankie" version, or 14N7 tall bottle version with identical (least I think) internals as the famous Sylvania 6SN7W metal base tubes.

I have a single Sylvania JAN 7N7 with this construction, and then the others are either branded as Sylvania or rebranded GE - I have seen them rebranded as RCA as you noted. Almost certainly all Sylvania but I do believe more than 1 factory made these, because most of mine have the flattish top like the one in your picture, but I have a few with a much more rounded top which I would assume means one of two things, different factory with different tooling/practices the made the glass, or age of manufacturing.

The most interesting thing imo about these specific 7N7/14N7 variant is I don't think there is a 6SN7/12SN7 "twin" with the same internals, flashing and carbonized coating just with octal base, like I believe most, if not all the others have. Maybe I am wrong here though, wouldn't be the first time.

But ya, it's a very lovely tube and glad I have a good stock of them in my collection.


Edit: Here a picture comparing the shape of the glass between the two different types I have.

It’s puzzling. Every other tube manufacturer only ever did the grey coating on their earliest tubes. Sylvania was supposed to be the maker of all but the NU 7n7. So why aren’t there any other Sylvania tubes like these? I don’t know of any other manufacturer that had this combo of grey glass and top getter like these. Old Sylvania 6sn7 had extensive getter flash all down the sides when it was at the top. I’m guessing the grey coating is precisely put on and covers up the rest of the getter flash. If only someone had a dead one that could be donated to science!

I might have to revisit these at some point because I wasn’t as enamored with these as I was with some of the other versions. My 14n7 that look like this sound different to the 7n7. At least that’s how I remember it. I recall complaining here about not liking them as much.

 

[Isaacc7]

Found a pair of NU round plate 7n7 on eBay. Was thinking ooh, he doesn’t know what he has and then I looked at the price. He’s one of those sellers that puts crazy prices on everything it seems. He is selling other more common 7n7 for more lol. I don’t know if there are priced fairly or not considering how rare they are.

https://www.ebay.com/itm/166455196034

I already have a pair so I’m not going to bite on these. I got mine by doing a bulk buy from a tube dealer and asking for tall 7n7. Got 3 of these, 3 or 4 of the frankies, and a bunch of regular tall bottle 7n7. All fine tubes and all at the same price. The dealers that have massive inventories often times don’t understand what they actually have. On the flip side many of them won’t cater to audiophile whims either. At least not for cheap tubes.

 

[g0ldl10n]

I might have to revisit these at some point because I wasn’t as enamored with these as I was with some of the other versions. My 14n7 that look like this sound different to the 7n7. At least that’s how I remember it. I recall complaining here about not liking them as much.

I actually have this same sort of opinion on 14N7 vs 7N7 sound quality in general - meaning, I have found for me personally, any 14N7 and 7N7 I have with identical construction only varying in heater voltages the 14N7 has always sounded better to me - why this is, I have no idea, but it was so consistent in what I was hearing I stopped buying 7N7 types all together, and only kept stocking up on 14N7 tubes.

 

[WildPhydeaux]

Not to muddy the waters but Sylvania also mixed chrome flashing with the grey coating on other tubes, like this 6F8G.

I note both with this tube and the 7N7 I referenced earlier that there is a distinct crisp line between the grey coating and the getter flash. In several cases, however, there are a couple areas where the coating has been scratched off and the missing grey is filled with silver getter.

This tells me the glass tube had the grey coating sprayed on the inside, somehow masked off to create the sharp edge. Then, when the internal structure was put into place the assembler allowed it to scratch the inner glass during insertion. Later after the tube was sealed and was induction heated to flash the getter it filled the scratch. I'll bet that inside the tube the getter is just as irregular as we normally see, just masked by the grey coating.

I would offer up a 7N7 for forensic examination, but not one of the ones we're most curious about unless one dies on me!

Cheers,
Robert

 

[Isaacc7]

Not to muddy the waters but Sylvania also mixed chrome flashing with the grey coating on other tubes, like this 6F8G.



I note both with this tube and the 7N7 I referenced earlier that there is a distinct crisp line between the grey coating and the getter flash. In several cases, however, there are a couple areas where the coating has been scratched off and the missing grey is filled with silver getter.

This tells me the glass tube had the grey coating sprayed on the inside, somehow masked off to create the sharp edge. Then, when the internal structure was put into place the assembler allowed it to scratch the inner glass during insertion. Later after the tube was sealed and was induction heated to flash the getter it filled the scratch. I'll bet that inside the tube the getter is just as irregular as we normally see, just masked by the grey coating.

I would offer up a 7N7 for forensic examination, but not one of the ones we're most curious about unless one dies on me!

Cheers,
Robert

Right, now that you mention it I’m pretty sure I have seen Sylvania 6l6g with the carbon coating and silver getter. I find it odd they didn’t do it with the 6sn7. As my posting about the 7f7 and 14n7 shows they were hardly consistent.

 

[g0ldl10n]

Not to muddy the waters but Sylvania also mixed chrome flashing with the grey coating on other tubes, like this 6F8G.



I note both with this tube and the 7N7 I referenced earlier that there is a distinct crisp line between the grey coating and the getter flash. In several cases, however, there are a couple areas where the coating has been scratched off and the missing grey is filled with silver getter.

This tells me the glass tube had the grey coating sprayed on the inside, somehow masked off to create the sharp edge. Then, when the internal structure was put into place the assembler allowed it to scratch the inner glass during insertion. Later after the tube was sealed and was induction heated to flash the getter it filled the scratch. I'll bet that inside the tube the getter is just as irregular as we normally see, just masked by the grey coating.

I would offer up a 7N7 for forensic examination, but not one of the ones we're most curious about unless one dies on me!

Cheers,
Robert

I think I might have one of these 7N7 tubes that are testing extremely low, to the point of SQ degradation, but will have to confirm. If so, I'll crack it open and take a look.

 

[GridIroN]

Hey gents, was wondering if I could grab some info from anyone around here in the know regarding MELZ 1578 tubes. I find myself trying to source a pair, and i'm coming across some interesting and conflicting information. I have some sources in Ukraine who claim to have found some, however the tubes do not have the "1578" logo nor the traditional "OTK" printing on the baseplate, but do have the same physical build indicators (top micas, 5 holes).

Using my google-fu, the consensus seems to be that without the "1578" logo, and the "OTK", it's not real, it's just a 68HC or other derivative made with similar tooling from surplus 1578 components. However, I've found commentary online claiming various 1578's destined to be used in the Soviet Nuclear and MiG fighter jet programs were produced without these markings...

Anyone here taken the plunge on unmarked MELZ tubes?

 

[LobalWarming]

Hey gents, was wondering if I could grab some info from anyone around here in the know regarding MELZ 1578 tubes. I find myself trying to source a pair, and i'm coming across some interesting and conflicting information. I have some sources in Ukraine who claim to have found some, however the tubes do not have the "1578" logo nor the traditional "OTK" printing on the baseplate, but do have the same physical build indicators (top micas, 5 holes).

Construction details are more important than print on the glass or base. For every tube, not just Melz.

Using my google-fu, the consensus seems to be that without the "1578" logo, and the "OTK", it's not real, it's just a 68HC or other derivative made with similar tooling from surplus 1578 components. However, I've found commentary online claiming various 1578's destined to be used in the Soviet Nuclear and MiG fighter jet programs were produced without these markings...

Anyone here taken the plunge on unmarked MELZ tubes?

I have a few 'unmarked' or mis-marked 1578 68HC that I enjoy as much or more as my bona fide 1578s. Especially since the later editions of 1578 from the 70s-80s sound too brash and harsh to me compared to the versions from the 50s-60s.

That would be actual issue for me. The manufacturing date of the 1578s. In which case I'd contact @Paladin79, our resident 1578 guru.

 

[Paladin79]

Construction details are more important than print on the glass or base. For every tube, not just Melz.

I have a few 'unmarked' or mis-marked 1578 68HC that I enjoy as much or more as my bona fide 1578s. Especially since the later editions of 1578 from the 70s-80s sound too brash and harsh to me compared to the versions from the 50s-60s.

That would be actual issue for me. The manufacturing date of the 1578s. In which case I'd contact @Paladin79, our resident 1578 guru.

PM me photos if you like and do your best to photograph or read the date code in the Melz logo if you see it.

 

[LobalWarming]

PM me photos if you like and do your best to photograph or read the date code in the Melz logo if you see it.

Do you mean @GridIroN to PM you images? Or for me to send you an artist's rendering from my Melz hoard collection?

 

[Paladin79]

Do you mean @GridIroN to PM you images? Or for me to send you an artist's rendering from my Melz hoard collection?

lol he just contacted me. Like beer I tend to keep my Melz in six packs.