Tube Advice Request

jbreezy5 · April 2023

What are some of your favorite 6SN7s?

mhardy6647 · April 2023

I like 'em all.

RCA 5692 are nice.
These are branded Westinghouse, but RCAs they be.

https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Special-Red-Tubes-1948.pdf

jbreezy5 · April 2023

mhardy6647 wrote: »

I like 'em all.
RCA 5692 are nice.
These are branded Westinghouse, but RCAs they be.

https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Special-Red-Tubes-1948.pdf

Those are great-looking tubes indeed. Thanks!

mhardy6647 · April 2023

They don't just look nice.

michaeljhsda2 · April 2023

I really like these, keep in mind they are as big as KT 88's if space is an issue.
https://www.ebay.com/itm/314036536813

pitdogg2 · April 2023

mhardy6647 wrote: »

I like 'em all.
RCA 5692 are nice.
These are branded Westinghouse, but RCAs they be.

https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Special-Red-Tubes-1948.pdf

You had better have big bank to buy the 5692's today. They have tripled in price the last 3yrs.

I also agree with Doc there are a ton of great 6sn7's out in the wild.

It's hard to go wrong with any of the Sylvania's. Brown based 6sn7wa Sylvania are pretty sweet as well.

jbreezy5 · April 2023

pitdogg2 wrote: »

mhardy6647 wrote: »

I like 'em all.
RCA 5692 are nice.
These are branded Westinghouse, but RCAs they be.

https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Special-Red-Tubes-1948.pdf

You had better have big bank to buy the 5692's today. They have tripled in price the last 3yrs.

I also agree with Doc there are a ton of great 6sn7's out in the wild.

It's hard to go wrong with any of the Sylvania's. Brown based 6sn7wa Sylvania are pretty sweet as well.

I heard about the Sylvania’s being good on Youtube. This is good confirmation. Thanks!

Gonna have to see if I can nab a pair of the 5692’s too.

heiney9 · April 2023

Sylvania Chrome tops, the earlier the better. Early Tung Sols. You're going to find a lot of minor variations on build for these 2 brands.

Check out his recommendations

https://tubemaze.info/

I have an amp that uses 6SL7's a very close and lesser cost cousin.

My top 3 5SL7's and I beleive there are 6SN7 equivalents
1) 1949 - Brimar CV1985

2) Sylvania JAN CHS 6SL7WGT short black plate, square getter

tied for 2) Tung Sol 6SU7GTY

3) RCA 5691

Again these are 6SL7's, but look for the 6SN7 equivalent

The really great 6SN7's won't be cheap. I just looked at the current prices for 6SL7's....yowzers.

H9

heiney9 · April 2023

jbreezy5 wrote: »

pitdogg2 wrote: »

mhardy6647 wrote: »

I like 'em all.
RCA 5692 are nice.
These are branded Westinghouse, but RCAs they be.

https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Special-Red-Tubes-1948.pdf

You had better have big bank to buy the 5692's today. They have tripled in price the last 3yrs.

I also agree with Doc there are a ton of great 6sn7's out in the wild.

It's hard to go wrong with any of the Sylvania's. Brown based 6sn7wa Sylvania are pretty sweet as well.

I heard about the Sylvania’s being good on Youtube. This is good confirmation. Thanks!

Gonna have to see if I can nab a pair of the 5692’s too.

You're going to need a fat wallet. 5691's (6SL7 eq) and 5692's (6SN7 eq) have gone into the stratosphere. Sylvania's chrome tops have always been in demand, and now I see the cost has jumped a lot.

Good luck, with a lot of patience and determination you might be able to find a good deal.

H9

mhardy6647 · April 2023

6SL7 has a higher ampification factor than the 6SN7. Not really interchangeable with 6SN7s, although -- sometimes a workable swap. Depends on the circuit. The driver section of my amplifier is designed for the former (straight from the resistance coupled amplifier charts in the RCA Receiving Tubes manuals) but also sounds very sweet with the latter (albeit with less cojones, as one might reasonably expect).

A word of caution re: the aforementioned 5691. It is functionally like a 6SL7 but -- according to RCA -- draws twice the filament current. Only your power (or filament) transformer knows for sure if it can handle the load

invalid · April 2023

I'm thinking about trying some adapters and two 6j5 single triodes in place of one 6sn7.

heiney9 · April 2023

No, I wasn't suggesting he use 6SL7. I was merely stating that many of the 6SL7's I've heard that the 6SN7 of the same tube are going to sound just as good.

That's all........don't try to use a 6SL7 in place of a 6SN7 unless the manufacturer says it's ok. I was afraid by my posting about the 6SL7 it might be confusing.

Since I don't have any experience with 6SN7's directly, I was just relaying my 6SL7 experiences as a parallel to how the 6SN7 will sound with my faves.

H9

jbreezy5 · April 2023

heiney9 wrote: »

No, I wasn't suggesting he use 6SL7. I was merely stating that many of the 6SL7's I've heard that the 6SN7 of the same tube are going to sound just as good.

That's all........don't try to use a 6SL7 in place of a 6SN7 unless the manufacturer says it's ok. I was afraid by my posting about the 6SL7 it might be confusing.

Since I don't have any experience with 6SN7's directly, I was just relaying my 6SL7 experiences as a parallel to how the 6SN7 will sound with my faves.

H9

Understood. 👍

mhardy6647 · April 2023

Gotcha @heiney9

Faustin · April 2023

Been very happy with Sylvania chrome tops in my Bottlehead amps. Don't recall the year, somewhere in the 1960s.

jbreezy5 · April 2023

Thanks for the recommendations guys. I’m now a man of many 6SN7s!

jbreezy5 · April 2023

Getting acquainted with CBS (clear tops?) 6SN7s tonight.

Please correct me if I’m saying something wrong. Want to learn more about 6SN7s.

I must say “clear” is a good descriptor for the sonics of the CBS.

heiney9 · April 2023

Just remember with most tube the label printed on the base or glass isn't necessarily the tube manufacturer. It's all about the tube codes. Those give date and manufacturer. And when you are better acquainted internal structure. This is especially helpful when searching for another pair of the same tubes.

Real CBS 6SN7's are rare and are early. Those most likely aren't manufactured by CBS. I can't really tell without seeing all the markings and internal build. Sometimes it's a tedious process trying to identify the true origin of a tube.

Have fun rolling and listening. I would say once you find a tube or pair of tubes you really dig then try to identify what it is.

H9

pitdogg2 · April 2023

True CBS tubes will say CBS-Hyton. CBS bought Hytron in very early 1950's. The lettering is white. Red lettering was later after they dropped the Hytron name mid to late 50's. Shortly after 1960-61 GE started making all CBS tubes. Those look a lot like my late 50's CBS tubes I had. They had the same whip like getter with a square at the bottom. Parallel T plates like those were used by early Sylvania which had a dimpled foil getter under the plates near the bottom. GE also made similar tubes like those for a short time they had a big rectangular bottom getter. GE kept the same red CBS in the diamond. So yes it can get very confusing whether they are CBS or GE.
GE did the same with Ken-Rad when they bought Ken-Rad in Owensboro Ky

heiney9 · April 2023

I do see a code of CN on the base. CBS didn't use that type of date code I don't believe.

There are lots of variations because of the long glass and short glass.

I have yet to see a 1960's or later octal tube manufactured by CBS.

H9

jbreezy5 · April 2023

Any thoughts on the following article, which sounds like it may be over-simplifying things, a little?

https://tubesound.com/identifying-cbs-hytron-tubes/

The only lettering I can see on the bases is “AN”, and none on the perimeter of the glass. Top of glass says 6SN7GT, with “AR” just below that.

Right now I don’t want to remove the tubes to look for the hole at the bottom of the spigot, b/c enjoying the music.

heiney9 · April 2023

Yes, oversimplified.

I just wanted to caution you that a tube label can have nothing to do with who manufactured it.

I used to live and breath this stuff and I have forgotten a lot of specifics. I still have some old links, but some of my reference sites are no longer available.

H9

jbreezy5 · April 2023

Much appreciated. Once I receive that lot of 24 I’ll start researching the codes like you mentioned. Will be fun.

pitdogg2 · April 2023

I just wanted to caution you that a tube label can have nothing to do with who manufactured it.

This in spades^^^

Many of the manufacturers back in the day bought from each other back and forth.

mhardy6647 · April 2023

That they did!

Nowadays, buyers (and sellers) are pretty savvy -- but even now (well... maybe...) one may find a "diamond in the rough" with off-brand tubes; particularly tubes branded with radio/TV/organ manufacturers' names (e.g., Maggotbox Magnavox, Emerson, Admiral, Conn, etc.).
The other interesting opportunity comes from second-tier "brands" like International Servicemaster. Such tubes were generally bargain-priced commodity tubes sold to the service trade -- but those boxes might contain anything. Always worth a look.

A totally random eBAY/internet photo of an International Servicemaster-branded 12AU7.

Now -- since I am both very lazy and, shall we say, recollectionally challenged

, I am not sure these resources have been mentioned... but here are a couple of handy tools for "tube explorers". I apologize if this is old news to the OP!

EIA manufacturer codes:
There are many, many on-line resources devoted to these (since it was a list that's ebbed and flowed over many decades). Here're a couple of fairly useful ones:

https://tubemaze.info/eia-codes-to-id-tubes/
https://www.ecianow.org/assets/docs/EIAStandards/1.7.4_EIAcodes1961.pdf
https://el34world.com/Forum/index.php?topic=27470.0

Pretty much everything you'd want to know about the 6SN7 may be found starting on page 3 of https://worldradiohistory.com/Archive-All-Audio/Archive-Vacuum-Tube-Valley/Vacuum-Tube-Valley-Issue-11.pdf

VTV was a heck of a resource. WRH gets big points for managing to secure (apparently) the rights to host the whole run of VTV online in the form of searchable PDFs.

Ludwell Sibley (of Tube Lore fame) put together an index of VTV that may be handy (I just used it to find the 6SN7 issue!). I am not sure of the original source, and it is copyrighted, but I am taking the liberty to attach a PDF version here.

Thomas Mayer's "tube of the month" entry on the 6SN7 and its kin may be found at:
http://vinylsavor.blogspot.com/2014/02/tube-of-month-6sn7.html

Hope that some of this is helpful!

invalid · April 2023

That tube of the month has pretty good info, he even tells you how the later version GTA/GTB 6sn7 tubes have a max plate dissipation of 450 volts, as the older GT version has a plate dissipation of 300 volts.

jbreezy5 · April 2023

Today I received my lot of 24.

Made a day of measuring them in a recently acquired B&K Dyna-Jet Model 707 Tube Tester I picked up last weekend.

Obligatory photo:

jbreezy5 · April 2023

Had one tube that needs the base replaced, and only 2 or 3 with shorts and/or grid emissions. Sadly they were Sylvanias, but still had a couple usable Sylvanias, so all good. 😁

Many of the tubes that passed on Gm1 and Gm2 have reasonable life left considering their age.

Only a few with very limited life remaining, which I consider good choices for headphone listening with a single tube head-amp (a Lyr maybe?).

Tonight I swapped in Sylvania 6SN7GTBs. These are very balanced-sounding upon first listen. Definitely a different sonic signature than the CBS-labeled tubes I listened to last night. These have more body and seem a little more neutral. The CBS sounded clear/transparent/holographic, if a little more lightweight than the Sylvanias.

Whether the CBS are actually CBS/Sylvania/GE the verdict is still out (for this 6SN7 noob anyway). The spigot does have the hole in the bottom as mentioned in the article I referenced in an above post. There is also the whip-like square getter @pitdogg2), black T-plates (only 2 holes; tube maze’s #1 rated Sylvania’s look eerily similar but are 3-holes in the plates). I was transfixed with the sound of these; very enjoyable.

Thanks again to all for the guidance.

jbreezy5 · April 2023

Posting for personal reference. Epic head-fi thread on 6SN7s:

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

heiney9 · April 2023

Looks like a great 6NS7 resource. I see only 2 things to be weary of.

1) everyone has an opinion
2) many of the tubes he lacks giving very specific construction descriptions.

One really needs to know construction specifics, because labels can NOT be trusted. So when he says, "black plates, top small getter w/yellow labels". That's not going to help pick out a rebranded tube of the real deal tube.

Otherwise a very interesting read and some very good information. A good reference site for sure. @treitz3 started a tube information thread awhile back to keep everything all in one place, this would be a good addition.

Sorry @jbreezy5, I don't know you name. But this is exactly how you go about gaining knowledge about tubes. For me when I was totally submersed for all those years, the gathering/gaining of knowledge and the hunt were equally as fun as rolling the tubes.

I scored so many great deals searching out holy grail tubes that were rebranded. Many times the seller had no idea. But knowledge of production codes and tube construction cues were necessary.

H9

pitdogg2 · April 2023

I read that years ago. Most if not all of the links are now dead, shame as it had great pictures of tubes and their construction.
(I didn't check all the links, all the links I checked were DOA)

I agree with one statement he made GE tubes with the exception of the 5682 to my ears they are not bad tubes but they are not good tubes. For me that includes all the small signal tubes as well. Every 12-au/ax 7, 5814 and 5751 to my ears they are tizzy. There is a bit of distortion to them I find unpleasant. That being said I did find a set of GE 6sn7 tubes that were pretty darn good. The 6sn7 bridged filament tubes were like no other 6sn7. You can tell them because the filament comes out of one triode across the top and down into the second triode. This filament stays red hot the whole time the tube is in use. Now I did find some that were built the same way by RCA. They are not the same tube at all. In looks only. The difference being as you start the tube the filament glows red hot and then goes out. Unlike the GE tube that stays scorching red hot the whole time it is in use. Whenever I'd use the GE tubes people that came to my house for just mesmerized by the Red Hot wire going across the top of the tubes.
Those GE bridged filament were made in both standard bases and coin base.

https://www.ebay.com/itm/143395295529

https://www.ebay.com/itm/143543495996

Now to see them at this price 15 years later WOW have they went up!
I bought pairs of them for $20.

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