The Reference 6SN7 Thread

[SuperRoo]

https://www.vivatubes.com/new-matched-pair-2-psvane-6sn7-uk-black-plates-gold-pins-vacuum-tubes/

 

[Odin412]

So far I’m just basing purchases on aesthetics. Lol.

Buying tubes can often be a crapshoot (meaning you can't tell which tubes will work well with which amps and which headphones in advance - at least I can't) so you might as well buy tubes that look good IMHO.

 

[Isaacc7]

I have been very pleased with the “Frankie” 7n7 combined with the current bring Sol branded 7581a in my SE amp. It sounds bigger and airier than other tubes I’ve tried with these output tubes. If I wanted to criticize the combo I guess I could say it sounds soft. But a kind of nice, ambient kind of soft. The bass is a bit wooly but fun and the high end isn’t as incisive but a great overall presentation.

It’s always nice when you discover a great tube and it’s one you already own!

 

[DenverW]

Just another PSA regarding sylvania 6sn7: just because a seller labels their tube as a ‘bad boy’ and charges a premium doesn’t make it one.

The ‘bad boy’ designation refers to specific tubes released for just over a year from late 1951 to early 1953. They will have a bottom getter and three holes in the plates.

You’ll find sellers all over the place that either aren’t aware of this or don’t care, and charge over $100 bucks for a tube you can get on the cheap.

 

[Novik tube]

Hello all.
I have had a lovely Melz 1578 matched pair for a few years now and they are still probably my favourite 6SN7s. I have had the pins resoldered (twice!) and they are dead silent and just perfect except for a minor issue which I mention below. They are fine examples of this tube but I have a couple of questions if I may...

Date of manufacture
If you look at the attached pics I am actually trying to determine the date of manufacture. The golden print in the first picture reads "6H8C X-76". I know it may seem very obvious but I assume the date of manufacture is 1976? Other markings on the tube are "OTK 23", "37" and "19" in a diamond logo. I think some of these indicate a simple quality assurance code but i'm not sure.

Stainless Steel Rods
Second question is that I note that the rods on mine are stainless steel. Well they are shiny. Looking at the 4th post here this fellow says this is a sign that they are the genuine Melz. However I see a lot of these where the rods do not appear to be stainless steel (not even in the picture in his post). These rather expensive ones do not seem to have stainless steel rods either. It may be that the pictures aren't picking it up but does this mean they are not genuine or just not the best versions? I would never pay that much for the tubes anyway but just curious. I know some people aren't as impressed with these as I am so perhaps some of these factors play a part.
I am quite curious about these as they look identical to the super expensive pair in construction. I appreciate they don't say 1578 on then either and are the 68NS variant but they have the "mouse ears" and the plates with the slight rectangular ledge.

Loose Base
The black base is very slightly loose at the base of one tubes. I have indicated where with a red box. It is a very tiny amount of play and it still works fine. I am not concerned about it however I would like to try and fix it so it doesn't get worse. I suspect it's because they have been rolled in and out a number of times and I would always pull them out by the metal base. Potentially I should have held them from the black plastic base instead. I use the woo audio ceramic socket savers.
I have been reading this thread and bought some superglue as well as an epoxy stick. The thing is, the play is probably less that 1mm so the Epoxy does seem overkill - especially as that area won't get hot so I don't think i'll use that.

Should I just apply some superglue in the gap between the metal and the plastic base? Or just leave it alone?

Thanks in advance

I would like to give you some information that (I hope) will be useful not only for you!
Yes, you definetely have a 6N8S tube from the MELZ plant produced in 1976 with a perforated anode (round holes).
Also on the tube there is the sign "1578", which indicates that this is a batch of 6N8S intended for the nuclear industry!
However, this statement is not 100% correct! Since 1949, tubes have been found only with "1578" and without "6N8S"
Taking into account the very high current cost of these tubes, I have been trying for several months to systematize the available information and am far from the end of this path. It looks like a Soviet puzzle! I am currently collecting different samples from different years.
No one has ever made stainless steel pins!
These are options for copper tubes of different wall thicknesses with different types of coating
I know this for real (I am attaching a photo - these are dismantled MELZ tubes from 50 to 89, which I use in my work!
Therefore, some of the posts on resuscitation of pins and soldering of wires on this thread really puzzled me!
I have attached a photo of the current collection, but this is just the beginning!
Yes! and the fact that someone rolled up "Brimar" on ordinary 6N8S ($3-9 per piece depending on the quality of the matching) from the Novosibirsk (NEVZ) plant of the 1980s - this is only marketing trick.
Pure modern marketing - nothing to do with reality

 

[TLO]

I would like to give you some information that (I hope) will be useful not only for you!
Yes, you definetely have a 6N8S tube from the MELZ plant produced in 1976 with a perforated anode (round holes).
Also on the tube there is the sign "1578", which indicates that this is a batch of 6N8S intended for the nuclear industry!
However, this statement is not 100% correct! Since 1949, tubes have been found only with "1578" and without "6N8S"

I dont quite get you...I am really confused with that statement. Below is a pair of MELZ 6N8S / 6H8C, made in 1956, I used to have.

 

[OctavianH]

I would like to give you some information that (I hope) will be useful not only for you!

Thank you for the information. You are the Ebay seller of russian tubes / adapters from here, right?

 

[Novik tube]

I dont quite get you...I am really confused with that statement. Below is a pair of MELZ 6N8S / 6H8C, made in 1956, I used to have.

Please excuse me for misleading you. Unfortunately, I speak English very poorly and use a translator to write posts.

In the sentence you highlighted, I meant that since 1949 there have been tubes with different markings. Some have only "6Н8С" on them, some have only "1578", some have both inscriptions. I have attached photos of similar examples with highlighted captions to this post.
Based on the Soviet documentation I checked and the evidence of those years, my main version at the moment is as follows:
6H8C is the name of the tube model itself. It appears in the technical documentation for this tube of those years. It was this name that was used as a designation.
"1578" is most likely NOT the designation of the model, I could not find such an index in the technical documents of the manufacturer's factory.
"1578" is most likely the acceptance stamp, or the stamp of the customer of certain batches of 6H8C tubes supplied to a certain enterprise or purchased by a certain department (probably the Ministry of Atomic Energy)
Most likely, the tubes bearing the stamp 1578 had additional quality control from the customer and/or during the production process.
In my collection there are examples of tubes that at first glance do not have the inscription 6Н8С, but at the same time there is an inscription 1578. But upon closer examination of the tube glass, you can see signs of the erased (over time) name 6Н8С.
I assume that due to the different technology of not applying these two stamps, after many years there were a large number of tubes on which the stamp “6Н8С” was completely erased, and “1578” remained. This is what "created" the new tube model, although this is not entirely true.

 

[TLO]

Please excuse me for misleading you. Unfortunately, I speak English very poorly and use a translator to write posts.

In the sentence you highlighted, I meant that since 1949 there have been tubes with different markings. Some have only "6Н8С" on them, some have only "1578", some have both inscriptions. I have attached photos of similar examples with highlighted captions to this post.
Based on the Soviet documentation I checked and the evidence of those years, my main version at the moment is as follows:
6H8C is the name of the tube model itself. It appears in the technical documentation for this tube of those years. It was this name that was used as a designation.
"1578" is most likely NOT the designation of the model, I could not find such an index in the technical documents of the manufacturer's factory.
"1578" is most likely the acceptance stamp, or the stamp of the customer of certain batches of 6H8C tubes supplied to a certain enterprise or purchased by a certain department (probably the Ministry of Atomic Energy)
Most likely, the tubes bearing the stamp 1578 had additional quality control from the customer and/or during the production process.
In my collection there are examples of tubes that at first glance do not have the inscription 6Н8С, but at the same time there is an inscription 1578. But upon closer examination of the tube glass, you can see signs of the erased (over time) name 6Н8С.
I assume that due to the different technology of not applying these two stamps, after many years there were a large number of tubes on which the stamp “6Н8С” was completely erased, and “1578” remained. This is what "created" the new tube model, although this is not entirely true.

Thank you for the clarification. Yes, 1578 is the same as 6H8C, it is just another level of certification for the said Ministry of Atomic Energy. Just like VT-231 to 6SN7GT.

 

[Novik tube]

Thank you for the information. You are the Ebay seller of russian tubes / adapters from here, right?

I am a relatively young participant in this forum and I try to be careful with its rules.
I study a lot more than I write myself! Photos with tube sockets boxes were superfluous in my post.
At the time, I read a post about pin recovery-a whole dissertation on how not to do it.
You are right about the store link.

 

[SuperRoo]

I have his tube savers and are very happy with them. Better quality than my old ones.

 

[TLO]

I have his tube savers and are very happy with them. Better quality than my old ones.

Yeah, I can see they are very well made. I have always thought about those metal base on Russian made tube of very high quality and wondered if anyone has collected them for DIYs.

 

[ThanatosVI]

I have his tube savers and are very happy with them. Better quality than my old ones.

I use Deyans but these look great as well

 

[triod750]

Sometimes you see these round hole plate 6H8C tubes without the 1578 designation. I have read that these are fakes. When I discussed this with a Ukrainian seller he assured me that they are the real deal and suggested that if I found any I should buy them since they might be cheaper due to this rumour. He has sold plenty of 1578 and has also compared them to 'the fakes'. But I make do with standard plate 6H8C from -52 and -55 and put my money elsewhere.

 

[K3cT]

Speaking of Eastern European tubes, my tube man just let me another interesting one. This 6SN7GTA has Telefunken markings but based on his info and from here it seems likely that this is made by RFT. Curiously the ring getter looks very TFK-ish though…

I haven’t had the time to test it yet, maybe tonight.