Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Jun Sun 24, 2018 4:13 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 23 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Wed 03, 2018 9:04 pm 
Member

Joined: Apr Sat 16, 2011 2:25 am
Posts: 388
Location: Victor, MT USA
Hi, I got about 10 of those red base 6SN7 RCA's, and I noticed they bring a lot of dough online. Why is this? Could anyone tell me how much these used pulls are worth. I checked them all in the tester and they tested good. I think I got some brown based ones too but they don't seem to bring as much online...If anyone can advise me I'd appreciate it..thanks, Alan

_________________
Don't worry about old age; it doesn't last that long.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Wed 03, 2018 11:02 pm 
Member

Joined: Aug Sat 02, 2014 3:59 am
Posts: 988
Location: Brooklyn, NY 11217
Cannot speak as to prices, but it is all cache of the "sound." They were uprated, so the audio crowd eats them up. I prefer el cheapo 6SN7s, or rewire the unit to use 12SN7s if the transformer allows because they are 1/4 the price.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Thu 04, 2018 11:43 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7697
Location: Long Island
The red base 6SN7s were premium long-life tubes for high reliability applications like analog computers, commercial communications equipment, and similar uses. Although the specs were tighter overall, they did not perform better than regular 6SN7s. They just lasted longer. They've been sought after for years by audiophools because they are not as common and therefore confer superior-sounding bragging rights on their owners.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 05, 2018 12:04 am 
Member

Joined: Oct Thu 02, 2014 5:57 am
Posts: 602
Location: Memphis, TN
I thought the red base meant it had low oxygen copper in its construction? :lol:


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 05, 2018 12:39 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 36621
Location: Livermore, CA
Red base 6SN7GT may be marked 5692. Better internal support but operate the same. Price much higher for the audio group.

_________________
Norm


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 05, 2018 2:15 am 
Member
User avatar

Joined: Jul Mon 08, 2013 2:48 pm
Posts: 253
Chris108 wrote:
The red base 6SN7s were premium long-life tubes for high reliability applications like analog computers, commercial communications equipment, and similar uses. Although the specs were tighter overall, they did not perform better than regular 6SN7s. They just lasted longer. They've been sought after for years by audiophools because they are not as common and therefore confer superior-sounding bragging rights on their owners.


They don't even last longer as the common 6SN7GT if used at the same max.ratings. To get the stated 10,000 hours service considerable de-rating is mandatory:

" If the 5692 is operated at the higher maximum ratings of the 6SN7-GT, the full advantages of the 5692 will not be obtained" (from RCA's Special Red Tubes datasheet flyer, 1948)

I have a few of these but never was able to detect any difference in sound when compared to the garden-variety of 6SN7's. But I'm not an audiophool, nor do I subject my audio gear to 500g impact shocks, or 2.5g of continuous vibration for hundreds of hours...

You can identify Special Red 6SN7 tubes by the reinforced internal structures (extra rods around the plates) and I've seen brown based ones sold under other brandnames (G.E) but obviously manufactured by RCA with the same tooling and materials. For the audiophools ears only the RED based ones (RCA's trademark) sounds good and command the highest prices.

Sell them.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 05, 2018 2:30 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4284
Location: NJ, 07645
The metal based 6SN7's are commanding a very high price also. Go figure.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 05, 2018 3:40 pm 
Member
User avatar

Joined: Jun Wed 08, 2011 2:33 am
Posts: 6759
Location: Ohio 45177
Do not try to rationalize it, just enjoy your profit and keep some of the regular ones for your own uses. Now I have heard of people getting new stuff with the Chinese or whatever version of the tube and installing NOS vintage tubes and liking the sound better. Maybe that just means the current production devices are inferior quality. Which could happen if someone is trying to start from scratch and recreate old mature technology that had the bugs worked out of it, at the time.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sun 07, 2018 2:30 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 1207
Location: Sunbury, Ohio 43074
I have noticed with the audio crowd that the more expensive the tube, the better it "sounds" :-D (sarcasm alert). There may be a direct correspondence between money spent, and listening enjoyment. I have no idea really. I think my solid state amplifiers complete with transient intermodulation distortion sound rather good in the living room.

But I do think tube amps sound warmer. Possibly because they ARE warmer. Is there a similar link between temperature and money spent on tubes??

The thought that one 6SN7 might "sound better" than another brings to mind the eternal debate with audio mixers in the high end broadcast business ... these guys swear that one $400k audio mixing board "sounds better" than a competing one. I have to kind of chuckle and mutter something about 'operator error' . Perhaps a term known as "headroom" in a mixing board.... the max input level before a stage goes into clipping ... but my answer is always the same. Don't drive your system into clipping :)

but hey, a $150 NOS 6L6 just HAS to sound better than a brand new $25 one, right?

nuff said

_________________
He who dies with the most sheer tonnage of ancient test gear, wins!


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Mon 08, 2018 6:39 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 2757
Location: Lincoln City, OR
Greetings to the Forum:

I stopped worrying about the supply of 6SN7's when I found out (here on the Forum) that a 6CG7 / 6FQ7 was the same tube in a 9-pin miniature package. There are gazillions of these out there due to their use in TV sets. I've 3 6CG7's and 11 6FQ7's in stock right now.

BTW, the smaller 9-pin miniature package has shorter lead length from the internals to the tube pins, resulting in less inductive loss of high frequencies and a brighter more modern sound.... Think I can sell this nonsense on the auction site? :D

Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Mon 08, 2018 4:08 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 1207
Location: Sunbury, Ohio 43074
Quote:
Think I can sell this nonsense on the auction site? :D

In a word "yes". To add a bit of encouragement for you : "it is a foregone conclusion" :)

_________________
He who dies with the most sheer tonnage of ancient test gear, wins!


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Mon 08, 2018 8:36 pm 
Member

Joined: Jul Sun 09, 2006 3:11 am
Posts: 5439
Location: Aurora, CO
If I run into them I sell them as quickly as possible. The few audio apps I've had that used 6SN7 sounded the same no matter what version I used. Don't we all have dozens of them in our tube stashes?

_________________
ex nihilo nihil fit


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Mon 08, 2018 10:19 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 32720
Location: Maryland 20709, USA
Norm Leal wrote:
Red base 6SN7GT may be marked 5692.
Better internal support but operate the same. Price much higher for the audio group.

There's much more to the RCA Special Red tubes than the red base.

Here's the datasheet on the entire series (5691, 5692, 5693):
https://frank.pocnet.net/sheets/084/5/5691.pdf
I have an original hard copy of that datasheet.

RCA also published a small booklet explaining the differences between the Special Red tubes and regular tubes from which they were derived. One of the major items is tighter tolerances. I have that booklet, and will scan it if I can find it.

There was also a rectifier (?5694?) added to the series after this datasheet was published.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Tue 09, 2018 1:19 am 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 1207
Location: Sunbury, Ohio 43074
Do the red base tubes sound red also ?? :-D

_________________
He who dies with the most sheer tonnage of ancient test gear, wins!


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Fri 12, 2018 7:35 pm 
Member

Joined: Aug Sat 02, 2014 3:59 am
Posts: 988
Location: Brooklyn, NY 11217
No; but there is a red shift, so it sounds like it is moving away from you.


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sat 13, 2018 11:08 pm 
Member
User avatar

Joined: Jul Mon 08, 2013 2:48 pm
Posts: 253
Leigh wrote:
Norm Leal wrote:
Red base 6SN7GT may be marked 5692.
Better internal support but operate the same. Price much higher for the audio group.

There's much more to the RCA Special Red tubes than the red base.

Here's the datasheet on the entire series (5691, 5692, 5693):
https://frank.pocnet.net/sheets/084/5/5691.pdf
I have an original hard copy of that datasheet.

RCA also published a small booklet explaining the differences between the Special Red tubes and regular tubes from which they were derived. One of the major items is tighter tolerances. I have that booklet, and will scan it if I can find it.

There was also a rectifier (?5694?) added to the series after this datasheet was published.

- Leigh


RCA's Special Red series rectifier tube was the 5690, a very peculiar tube and unlike the other Special Red tubes its design was not based on any regular receiving tube and has no equivalents. Also, the 5690 is amongst the very few full-wave (dual) rectifier tubes with separate cathode connections allowing for common anode, common cathode or any other circuit configurations. A beautifully made tube, maybe the "King of Rectifiers", but sadly ignored by most audiophiles.


Attachments:
5690.02.jpg
5690.02.jpg [ 180.84 KiB | Viewed 942 times ]
Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sat 13, 2018 11:18 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 1207
Location: Sunbury, Ohio 43074
OH, we all realize that the red base tubes were a highly "industrial" version of the standard 6SN7. .. but I'm still thinking it sounds red, or has some kind of red shift thing going on as noted. Or maybe red matter (not to be confused with dark matter) ... does it really matter ? :-D

_________________
He who dies with the most sheer tonnage of ancient test gear, wins!


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sat 13, 2018 11:27 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 32720
Location: Maryland 20709, USA
The red base was used so a tech looking at the underside of a set could confirm that the proper tubes were installed.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sat 13, 2018 11:38 pm 
Member
User avatar

Joined: Jul Mon 08, 2013 2:48 pm
Posts: 253
Barry H Bennett wrote:
OH, we all realize that the red base tubes were a highly "industrial" version of the standard 6SN7. .. but I'm still thinking it sounds red, or has some kind of red shift thing going on as noted. Or maybe red matter (not to be confused with dark matter) ... does it really matter ? :-D


Of course it does. The sound can be defined as dark reddish. You should know (as most audiophiles already do) that what defines the quality of an electron tube is NOT what's inside the glass but the material and color the BASE is made of. That's why the red (or better:metal) based tubes commands the highest prices, they just sound MUCH better than all-glass tubes which sounds thin and airy. (unless they carry a print of a little boy playing a bugle)


Top
 Profile  
 
 Post subject: Re: 6SN7 Red Base RCA's Why are so expensive?
PostPosted: Jan Sat 13, 2018 11:59 pm 
Member
User avatar

Joined: Jul Tue 15, 2008 6:13 pm
Posts: 4954
Location: Gretna, Nebraska
Lets not forget the other inherent audio qualities of the tube's plate color (aside from red) and the location and size of the getter. All key to a high performance tube.

_________________
http://www.vintagerestorationservices.com
Paul
...... how hard can it be?


Top
 Profile  
 
Post New Topic Post Reply  [ 23 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: radiodale1 and 7 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB