The Reference 6SN7 Thread

[JKDJedi]

Hey guys! Need a little 6sn7 advice. Maybe from you Mordy... see you online here, it's been a while for sure! So I've been looking for a holy grail 6SN7 tube. So far I tried the Melz 6SN7 type like this. I'm impressed by the organic/realistic quality and the rhythm is good, but a bit muddy and slow at times.

What about the esteemed type with holes as shown below. Would you recommend it's what I'm looking for and worth the extra cost?

Few others I already have are Sylvania silver glass authentic 'bad boy', Sylvania short glass 6sn7w chrome base, and tall Tung Sol 6sn7 brown base.

@Paladin79 is the man to talk to about these

 

[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.

As far as bona fide 1578’s the Russians used to stamp some with that number to drive the price up, often with magenta colored ink. I only pay attention to construction and date code.

 

[SuperRoo]

Mine are only 4 packs

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

Mine are only 4 packs.

 

[DecentLevi]

The best 6SN7 tubes have become quite pricey. According to many, and I concur as well, a pair of 6J5 family tubes will sound better and cost less. The 6J5 is 1/2 of a 6SN7. You will need a dual adapter to use them or two adapters depending on how your amp was made.
There is another tube that is electrically very similar to the 6J5 family - the 6C5. I would suggest a pair of metal 6C5 Ken-Rad tubes - can be found very inexpensive and sound great.
The 6J5/6C5 tubes come as metal, GT and G versions and there is plenty of reading material to figure out what may be best for you.
You could also look for Russian versions of the 6J5GT tubes - 6C2C which should be very reasonably priced compared to the Melz.

Aside from fit issues, the other reason I'm not planning to go thr 6J5 route (although that would be nice) in my current amp is that it takes 2x 6SN7 so I would have to arrange pairs of 4x 6J5... then there's the adapter issue. I'm the minority on this one, but I've developed an impression that direct contact sounds better. From a few in depth critical listening tests with/without socket savers, and drawing on deep experience with direct tubes vs. with adapters, I see the general difference being more of an intimate, vivid, true-to-life sound picture with a certain fullness to the sound, vs. a slightly more distant and even thin sound with adapters. I've had both made in China and boutique adapters from Deyan, but now I'm trying this new seller I found on eBay from Kazakhstan who said he will use premium conductor materials, to see if that sounds any better than the likes of Xu Ling's offerings

 

[robo24]

I have some 1578s with that stamped and some without but the key is the plates have holes and the top mica like these, not the clear ones. They have to be metal.

Different plate on those with mylar on the ends I haven't heard, but I did have these

and they were very run of the mill tubes I quickly sold off.

I don't know if you've seen this, but the ones are the left are the ones to get.

 

[paradoxper]

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?

This is pretty common. Who is the eBay seller?

 

[Paladin79]

Aside from fit issues, the other reason I'm not planning to go thr 6J5 route (although that would be nice) in my current amp is that it takes 2x 6SN7 so I would have to arrange pairs of 4x 6J5... then there's the adapter issue. I'm the minority on this one, but I've developed an impression that direct contact sounds better. From a few in depth critical listening tests with/without socket savers, and drawing on deep experience with direct tubes vs. with adapters, I see the general difference being more of an intimate, vivid, true-to-life sound picture with a certain fullness to the sound, vs. a slightly more distant and even thin sound with adapters. I've had both made in China and boutique adapters from Deyan, but now I'm trying this new seller I found on eBay from Kazakhstan who said he will use premium conductor materials, to see if that sounds any better than the likes of Xu Ling's offerings

I have conducted blind listening tests and if a person could tell me when the same tube was in adapter or not I would certainly be impressed but they would have to do that without seeing when it happened. There would also have to be several samples so it is not a 50/50 chance.

 

[Isaacc7]

I know this is the 6sn7 thread but we have talked about various twin triodes as well here. Thought I'd say a few things about a tube I was told was a decent replacement for the 6sn7.

A lot of people think the ecc32 is the best 6sn7-ish tube out there. To be clear, it is not a drop in replacement for a lot of amps even though it is pin compatible. It draws 1 amp of heater current. Anyway, the ecc32 is now priced into the stratosphere and I'm never going to spend the money on one. I had been told that the ecc31 with the right adapter sounds pretty much like the ecc32. The ecc31 is a lot cheaper so I gave it a shot.

I could never get good sound with it. It always gave me a diffuse, phasey kind of sound. It sounded weak and unfocussed. Looking at the data sheets and like its 6n7 cousin it was designed as a class B push pull tube when the triodes are used separately and as a driver when the triodes were paralleled turning it essentially into a single triode. Falling for the sunk cost fallacy I went ahead and ordered an adapter that uses 2 ecc31/6n7 in place of a 6sn7.

I'm glad I did. The sound is much much better. Hard to believe using a tube the way it was designed is better lol. Anyway, the 6n7/ecc31 makes a much better driver than dual triode. Watch out for heater current though! I'm using 4 of them and dissipating 22 watts of power just for the heaters of my drivers. One other thing, you can actually have the adapter wired so that you can use either 6n7 or 6j5 tubes in the same adapter. If you have one made you might as well get both options.

 

[leftside]

I'm glad I did. The sound is much much better. Hard to believe using a tube the way it was designed is better lol. Anyway, the 6n7/ecc31 makes a much better driver than dual triode. Watch out for heater current though! I'm using 4 of them and dissipating 22 watts of power just for the heaters of my drivers. One other thing, you can actually have the adapter wired so that you can use either 6n7 or 6j5 tubes in the same adapter. If you have one made you might as well get both options.

Or an amp that can accept 6J5 or 6N7 tubes in the same sockets

I agree with you on the ECC32. Sound terrible in my preamp but amazing in two of my amps.

 

[Isaacc7]

And while I'm on the topic of twin triodes I'll leave this here as well. Internet wisdom says that Sylvania made all of the 7n7 (except the round plate NU) and 7f7 tubes and that they are the same as their regular 6sn7 and 6sl7 tubes respectively. That is mostly true, you can see the different versions of the 6sn7 reflected in 7n7 construction save for the earliest metal base 6sn7wgt. Oddly enough, the 14n7 seems to have a similar (identical?) build that isn't seen in any other 6sn7, 7n7, or 12sn7. I think the 14n7 is the best sounding out of all of the Sylvania *sn7 variants.

I noticed something similar with the 7f7. Sylvanina made a metal base 6sl7wgt that seems to be considered their best sounding. It is of course very rare and expensive these days.

Notice the copper support rod. It is unique in the 6sn7wgt/14n7 and 6sl7wgt. Well look what I found when I pulled out some 7f7 made for the US Army Signal Corps.

There's that copper support rod. I have found this construction in 7f7, 14f7, and 12sl7 but not the 6sl7. They aren't exactly the same tube. The micas are just slightly different and most of the tubes I have found have black plates instead of the grey of the 6sl7w. I do have some of those too though. So how does it sound? Compared to the JAN Sylvania 6sl7gt with bottom getter (same vintage as the so called bad boys) the copper rod version sounds more refined, has better detail, and just smoother overall. That's with the black plate 7f7, haven't had a chance to compare to the grey plates yet.

I don't think they are exactly rare. Once I figured out what to look for I was able to find them with no problem. I don't think Sylvania made 7f7 for very long, they only ever seem to be of an earlier construction. These seem to be of the earliest batches. You might have trouble seeing any online right this second because, uh, someone bought the ones he saw. If you're patient I'm sure you'll see them crop up on eBay, reverb, etc. They were labeled all sorts of different ways, Sylvania, Zenith, Raytheon, Motorola, and probably others. The thing is those brands are also on regular 7f7/14f7 tubes as well. My initial tubes came in boxes branded with Hygrade Sylvania, a name they stopped using after 1946. It also seems like anything labeled GM is also probably the copper rod version. Those are the only two sure fire things I've seen so far. The others have to be determined just by looking at them. I just got a pair of 12sl7 that have the classic "chrome dome" getter flashing covering up the entire tube. The bay seller had happened to hold it up to the light so I could see the rod. I assume it's copper but there's no way of knowing for sure.

Anyway, thought I'd let you 6sl7 hunters in on a nice version.

 

[GridIroN]

Random question for fellow tubeheads...

Anyone know how one might run 12SN7s in a circuit designed for 6SN7s? It seems relatively trivial to step down a 12v signal to 6v but I can't find a readily available adapter without terminating in 9pin and having to re-adapt back to octal...

 

[sam6550a]

Random question for fellow tubeheads...

Anyone know how one might run 12SN7s in a circuit designed for 6SN7s? It seems relatively trivial to step down a 12v signal to 6v but I can't find a readily available adapter without terminating in 9pin and having to re-adapt back to octal...

The 12SN7 needs a 12V heater supply, so you must replace the 6V supply with an external 12V source. No adapters will do what you want to do. You need to contact a qualified tech to do this, it is not for the layman.

 

[GridIroN]

The 12SN7 needs a 12V heater supply, so you must replace the 6V supply with an external 12V source. No adapters will do what you want to do. You need to contact a qualified tech to do this, it is not for the layman.

So what you're telling me: I can watch one of those restoration youtube videos for 10min and handle this myself, no problem?

 

[Designsfx]

So what you're telling me: I can watch one of those restoration youtube videos for 10min and handle this myself, no problem?

Just fast forward to the part where the gear catches on fire and you can reduce the watch time to about 30 seconds…

 

[LobalWarming]

The 12SN7 needs a 12V heater supply, so you must replace the 6V supply with an external 12V source. No adapters will do what you want to do. You need to contact a qualified tech to do this, it is not for the layman.

So what you're telling me: I can watch one of those restoration youtube videos for 10min and handle this myself, no problem?

Sure thing. But 10 minutes is a pretty long time...

If Mrs. X was still in biz could buy one of her socket adapters for external heater power.

But you could build one yourself. Just intercept the heater pins (7,8) on the way through so as to not make an 18V adapter.