The Reference 6SN7 Thread

[LobalWarming]

I own several of the 6SN7W tubes and always felt they were excellent tubes with no differences heard between the metal base and black plastic base at all. And don't get me started on the KenRad VT-231 black vs clear glass... That said I find the 7N7 to more or less be the equal of the 6SN7W. I say more or less because some sounded slightly better than others, but it was by tiny, tiny degrees and could easily have been the past usage of the tubes or my mood when I listened - there was no obvious correlation to shape of mica, getter coverage, angle of the plates, support rods etc ad nauseum. I will admit that it would seem tubes with copper cathode rods have an edge to my ear. The 6SN7W do have support rods but as to whether they contribute to sound quality might just be conceivable - do they minimize microphonics? If so, why do the non-support rod 7N7 sound so close to the 6SN7W? Maybe a shorter bottle doesn't need support rods to be less prone to microphonics vs the tall glass bottles. Has anyone measured glass thickness? Copper cathode rods are not necessarily causation for better sound either, but there does seem to be a correlation.

Cheers,
Robert

And... as they say in the Audiophile Arts Department of Marketing: "Correlation IS causation"

 

[Isaacc7]

I own several of the 6SN7W tubes and always felt they were excellent tubes with no differences heard between the metal base and black plastic base at all. And don't get me started on the KenRad VT-231 black vs clear glass... That said I find the 7N7 to more or less be the equal of the 6SN7W. I say more or less because some sounded slightly better than others, but it was by tiny, tiny degrees and could easily have been the past usage of the tubes or my mood when I listened - there was no obvious correlation to shape of mica, getter coverage, angle of the plates, support rods etc ad nauseum. I will admit that it would seem tubes with copper cathode rods have an edge to my ear. The 6SN7W do have support rods but as to whether they contribute to sound quality might just be conceivable - do they minimize microphonics? If so, why do the non-support rod 7N7 sound so close to the 6SN7W? Maybe a shorter bottle doesn't need support rods to be less prone to microphonics vs the tall glass bottles. Has anyone measured glass thickness? Copper cathode rods are not necessarily causation for better sound either, but there does seem to be a correlation.

Cheers,
Robert

I don’t think that the micas, support rod, or getter flashing have anything to do with sound quality. I do think that they can point towards different batches or generations of tubes that do sound at least a bit different from each other. My working theory is that the copper rod versions are the earliest versions. Copper was phased out during the war as they found that other materials were just as good but cost less. Think there were copper shortages during the war too. Eventually they figured out they didn’t need the support rods at all. I also suspect the 7n7 and 14n7 production started before 6sn7 at Sylvania. As far as I can tell the metal based 6sn7w was Sylvania’s first 6sn7. Sylvania was trying to make their loctal base a competitor to RCA’s octal base. My theory is that Sylvania was making loctal for radio use in cars, planes, etc. and they got a contract to make octal 6sn7 for the military during the war. Once it became obvious that octal was taking over they stopped making most loctal tubes.

Looking over my 7n7 collection I see three different plate constructions and materials among the parallel t plates. What I assume are the oldest, some with support rod, have a kind of lumpy, less even black plate. At some point the black plates became smooth and uniform. Eventually they became grey but with a similarly smooth and uniform coating. Common wisdom is that older versions of tubes sound better than newer ones. I definitely think that’s the case with American 6sn7 tubes.

The metal based 6sn7w has always been seen as a grail 6sn7. Their rarity helped hype them up and added to the price. I had suspected the loctal tubes were equivalent and now that I have an actual 6sn7w to compare I now have some evidence. It’s enough for me. Well, if I think the actual 6sn7w sounds obviously better then I’ll reconsider but I doubt that’ll happen. I just wanted to share that it’s possible to get that old metal based 6sn7w sound without the cost. Same for the 6sn7 as well.

 

[WildPhydeaux]

For the record, my comments re: getter flashing, mica shape, etc not affecting the sound (to my ear) was not directed at you and in fact I'm of the same mind that they are valuable in so much as they can point to an era of build, should dating prove difficult. Some guys DO find direct merit in these details, I'm just not one of them for better or worse.

I would only question the following:

Bottom line, I think that any 14n7 will be the equivalent of the metal base Sylvania 6sn7w but 12v of course. If you are lucky you can find a 7n7 that will also be the same.

Are you referring to the build only here or the sound? Seems a stretch to assume the same sound based on build of different tube types and comparing sound against a decade old memory... well, I'm not sure I could compare last night's session to tonight. YMMV

Or do you have a system that uses just one such tube and you can therefore compare the single cracked base 6SN7W with the xN7 tubes?

Not trying to be provocative here, I'm on your side and curious about your actual ears-on findings.

Cheers,
Robert

 

[Isaacc7]

For the record, my comments re: getter flashing, mica shape, etc not affecting the sound (to my ear) was not directed at you and in fact I'm of the same mind that they are valuable in so much as they can point to an era of build, should dating prove difficult. Some guys DO find direct merit in these details, I'm just not one of them for better or worse.

I would only question the following:

Are you referring to the build only here or the sound? Seems a stretch to assume the same sound based on build of different tube types and comparing sound against a decade old memory... well, I'm not sure I could compare last night's session to tonight. YMMV

Or do you have a system that uses just one such tube and you can therefore compare the single cracked base 6SN7W with the xN7 tubes?

Not trying to be provocative here, I'm on your side and curious about your actual ears-on findings.

Cheers,
Robert

I do have an amp that can use either 6v or 12v input tubes. I haven’t replaced a cable to use it yet so I haven’t done the aural comparison yet. That amp only needs a single twin triode up front. Because of the similarity between the tubes with copper posts I anticipate similar sounds. My only solid memory of using the metal based 6sn7w is that I preferred them more than any other 6sn7 I had at the time. Flash forward to several years ago and the 14n7 had risen to the same heights among Sylvania tubes. The fact that I liked them more than the other versions and they looked like the same construction didn’t seem like a coincidence. We’ll see.

If the 6sn7w sounds better than the 14n7 I have been rotating through my system I will be convinced it is the best Sylvania. If it sounds the same I’ll be convinced it is the same. If it sounds worse I’ll think I got bad one

 

[WildPhydeaux]

Cool. It did occur to me after I posted that being this is primarily a headphone forum it was likely you did have an amp that used a single 6SN7.

Very curious to hear what you hear. So to speak!

Cheers,
Robert

 

[Isaacc7]

Cool. It did occur to me after I posted that being this is primarily a headphone forum it was likely you did have an amp that used a single 6SN7.

Very curious to hear what you hear. So to speak!

Cheers,
Robert

I don’t actually use headphones for music! I’m here for the tube discussion. My wallet would have been much better if I never stumbled across this place lol.

 

[babyoh]

Does anyone have experience with smoke glass 7N7? How does it sound compared to clear tall glass, "race track" oval 7N7? Thanks.

 

[Isaacc7]

Whew! Somebody finally replied!

Does anyone have experience with smoke glass 7N7? How does it sound compared to clear tall glass, "race track" oval 7N7? Thanks.

Sooooo…..

Going back a few posts I was trying to suss out the difference between the metal base Sylvania 6sn7w and the 14n7. The 14n7 has a copper support rod similar to some of the metal based 6sn7w but mine had the support rod made from some other material. The question was, are they same? Are they different?

Keep in mind I only have one 6sn7w. Bottom line, the 14n7 sounds different than the this 6sn7w. I prefer the 14n7, it feels smoother and richer to me. I have multiple 14n7, all with the same construction and they sound the same to me. I had anticipated that the tubes would sound the same so I’m a bit surprised. If my guesses are right, it means that the copper rod versions of these tubes (14n7, 6sn7w, 7f7, 14f7, 12sl7) are from an earlier batch or production run. But what about the 7n7? I have one tall bottle 7n7 clear glass with a non copper support rod. It sounds different than the 14n7. I have not had a chance to compare it to the 6sn7w yet (keep meaning to). In all my scouring of eBay etc. I never saw a 7n7 with a copper support rod. As my earlier post mentioned, it turns out the three tall bottle grey glass 7n7 I have do in fact have the copper support rod. You can see just a little bit above the bottom mica, enough to see the rod. I assume they are built the same as the other copper rod 14n7 but can’t see enough to confirm. I have one shorter bottle grey glass 7n7. The internals are completely hidden so I have no idea if it is the same construction or not. I suspect they probably are. Sylvania made very few grey glass tubes (I’ve only seen 6v6g anf 6l6g) and they were all very early versions.

I vaguely recall having a few back and forth posts in this thread I think (with @g0ldl10n ? @bcowen ?) about some grey glass 7n7 or 14n7 not sounding very good. That person seemed to associate a particular bottle shape but now I can’t remember. I’m positive that my bad experience was with a grey glass 14n7, think one that was completely opaque.

Bottom line is if you can see the copper post I think you have a great 7n7, possibly one of the best 6sn7 made. If you can’t then it’s hard to say. Go ahead and try it out and let us know!

 

[g0ldl10n]

I vaguely recall having a few back and forth posts in this thread I think (with @g0ldl10n ? @bcowen ?) about some grey glass 7n7 or 14n7 not sounding very good. That person seemed to associate a particular bottle shape but now I can’t remember. I’m positive that my bad experience was with a grey glass 14n7, think one that was completely opaque.

Here ya go - I actually find this variant as good, if not slightly better than the taller bottles with copper rods that look like same internals as the 6SN7W.

Post in thread 'The Reference 6SN7 Thread'

Aug 18, 2024

@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...

• g0ldl10n

• 

EDIT: I would imagine the different glass shape either means different factory/tooling, and or different production year(s), which imo, could cause differences in performance depending on how well each was made.

 

[triod750]

I have one metal base 6SN7A/W (A on glass and W on base). I also have a few 7N7. One of these has the same shape of bottom mica as the 6SN7A/W but no copper support rod. Top mica in 6SN7A/W is round while in the 7N7 it has the same shape as the bottom mica. I can't distinguish the sound from these two tubes I write about and they don't sound like the Frankentubes do. This 7N7 arrived in a sealed box with acceptance date 9-27-43, S.C. Order No 29360-PhiLA-43 TUBE JAN 7N7 and SC95A on glass and box.
Both of the above tubes have clear glass and about the same amount of flash.

Edit. The 7N7 doesn't have the same kind of umbrella spokes as the 6SN7A/W, probably due to the different shape of top mica. It's impossible to see the getter in the 6SN7A/W due to the chrome flash and round mica while in the 7N7 I can 'almost' see a square foil getter with a dimple in it. Looks like the getter in another Syl 7N7 with race track mica and no spokes at all.

 

[WildPhydeaux]

Does anyone have experience with smoke glass 7N7? How does it sound compared to clear tall glass, "race track" oval 7N7? Thanks.

I did a micro-review of four 7N7 types and a 7AF a while back. It reconfirmed to me what I had thought from several years ago - that I like the smoked glass/ chrome top 7N7 the best - but I was surprised at how closely they all sounded.

Apologies for the two-part post, I hadn't planned on doing a review when I posted the pictures and construction comments. Unlike @Isaacc7 I have never seen a 7N7 without copper rods...

https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-18291826
https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-18293306

Cheers,
Robert

 

[Isaacc7]

I did a micro-review of four 7N7 types and a 7AF a while back. It reconfirmed to me what I had thought from several years ago - that I like the smoked glass/ chrome top 7N7 the best - but I was surprised at how closely they all sounded.

Apologies for the two-part post, I hadn't planned on doing a review when I posted the pictures and construction comments. Unlike @Isaacc7 I have never seen a 7N7 without copper rods...

https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-18291826
https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-18293306

Cheers,
Robert

All of them have the copper rods through the plates. What I am referring to is a separate copper support rod that is outside the plates structure.

Here you can clearly see the copper rods through the plates structure and the prominent extra support rod. If you check the gap between the grey glass and the bottom mica I bet you’ll see that this rod is there as well.

 

[WildPhydeaux]

All my 7N7 tubes have copper rods in the plates. Of the ones with extra support rods, they too are copper.

I haven't heard any evidence, though, that the material the support rods are made of has any bearing on sound. Or, for that matter, that the subtle difference in sound between the tubes with support rods and tubes without are due to the existence of the support rods themselves, since the tubes have other construction differences.

I acknowledge variations in sound and performance, but it's subtle. And two tubes with identical construction, measuring the same on testers etc will often vary in sound. So I think pitting one example of a particular tube against another single example of a slightly different one doesn't exactly say much.

Cheers,
Robert

 

[Isaacc7]

All my 7N7 tubes have copper rods in the plates. Of the ones with extra support rods, they too are copper.

I haven't heard any evidence, though, that the material the support rods are made of has any bearing on sound. Or, for that matter, that the subtle difference in sound between the tubes with support rods and tubes without are due to the existence of the support rods themselves, since the tubes have other construction differences.

I acknowledge variations in sound and performance, but it's subtle. And two tubes with identical construction, measuring the same on testers etc will often vary in sound. So I think pitting one example of a particular tube against another single example of a slightly different one doesn't exactly say much.

Cheers,
Robert

I don’t think the rod itself has any bearing on sound quality either. I do think that it is an obvious way of telling different batches apart. I don’t see it as pitting them against each other so much as differentiating between them. The earliest metal based Sylvania 6sn7w are well regarded but super expensive. If you want that sound but don’t want to pay the price I am now convinced that these particular 7n7 and all of the 14n7 will give it to you.

I’m pretty confident the early Sylvania *sn7 timeline went something like this:

1) First versions of the octal based w versions made for the military with copper posts probably started in 42. Along with these the first 7n7, 14n7, 7f7, and 14f7 were also made with the copper support rod. I have copper rod 7f7 labeled Hygrade Sylvania, a name they dropped after 43. The Sylvania labeled 7f7 with copper post also have the green leaf logo on them which also points to being very early days. The grey glass 7n7 and 14n7 are unique in the Sylvania *sn7 world. The only other tubes Sylvania made with similar construction that I have seen are also their oldest versions of 6l6g, 6f6g, 6f8g, and 6c8g. There are probably others but they are all the oldest Sylvanias.

2) Next versions of at least the metal 6sn7w and 7n7 are made with a non copper support rod. I have never seen a Sylvania 6sl7, 7f7, or 14f7 with a support rod made of anything but copper. I have a Sylvania 12sl7 that has a support rod but because of the silvering I can’t tell what color it is. I assume it is copper but can’t prove it.

3) They kept making the metal base 6sn7w and 7n7 but now without a support rod at all. I’ve never seen a 14n7 without the copper support rod so I speculate they did not make them for very long.

What I still want to do is compare my 6sn7w to the 7n7 I have with the non copper support rod. I anticipate them to be the same tube with minimal if any differences. I also have an idea that the plate material or manufacturing technique changed with these over time as well. Seems like the oldest tubes have a lumpier black plate coating with less sharp detail. Then they went to a black plate with a very uniform, flat coating. After that they went to a grey coating that was so even it doesn’t even look like a coating at all. I *think* all the copper support rod tubes have similar looking plates and the 7n7 without a support rod looks different but I need to check.

@WildPhydeaux do any of your 7n7 with the copper support rod have clear glass? Do you have any pictures? I’d love to compare to the ones I have.

 

[g0ldl10n]

It's impossible to see the getter in the 6SN7A/W due to the chrome flash and round mica while in the 7N7 I can 'almost' see a square foil getter with a dimple in it.

Not impossible