[shipsupt]

Since moving to the UK I have noticed that the 6S4A is not a popular tube here. I don't know the history of the tube, but from my limited experience it appears to be far more available in the US.  I'm guessing this is the same across Europe, but again it's just a guess.  In fact when I checked with a couple of fairly established local vendors they had never heard or seen one...
 
I would recommend you search for US suppliers and contact them directly asking for what you are looking for instead of checking their on-line inventory.  I am sure they can put four tubes together for you with no trouble.  Here are few examples, I'm not endorsing any particular supplier:
http://www.vacuumtubesinc.com
https://www.tubeworld.com/6l6.htm
http://www.vacuumtubes.net
http://www.thetubestore.com
http://www.usatubeaudio.com

 

[wuwhere]

.

 

[Sahara]

Quote:

Since moving to the UK I have noticed that the 6S4A is not a popular tube here. I don't know the history of the tube, but from my limited experience it appears to be far more available in the US.  I'm guessing this is the same across Europe, but again it's just a guess.  In fact when I checked with a couple of fairly established local vendors they had never heard or seen one...
 
I would recommend you search for US suppliers and contact them directly asking for what you are looking for instead of checking their on-line inventory.  I am sure they can put four tubes together for you with no trouble.  Here are few examples, I'm not endorsing any particular supplier:
http://www.vacuumtubesinc.com
https://www.tubeworld.com/6l6.htm
http://www.vacuumtubes.net
http://www.thetubestore.com
http://www.usatubeaudio.com

 
Thank you very much, shipsupt. I'll contact with one of them to purchase a matched quad.
Do you know the brands have manufactured them?
 
I know Westinghouse ( information from Petnoff) but I dont know others brands..
Regards

 

[shipsupt]

RCA, GE, Dumont, Sylvania, International, Philco, CBS, and Trutone.  I am sure I missed a few...

 

[JDrive]

Since moving to the UK I have noticed that the 6S4A is not a popular tube here. I don't know the history of the tube, but from my limited experience it appears to be far more available in the US.  I'm guessing this is the same across Europe, but again it's just a guess.  In fact when I checked with a couple of fairly established local vendors they had never heard or seen one...
 
I would recommend you search for US suppliers and contact them directly asking for what you are looking for instead of checking their on-line inventory.  I am sure they can put four tubes together for you with no trouble.  Here are few examples, I'm not endorsing any particular supplier:
http://www.vacuumtubesinc.com
https://www.tubeworld.com/6l6.htm
http://www.vacuumtubes.net
http://www.thetubestore.com
http://www.usatubeaudio.com

 
Thanks for the list of places that might have these available. A lot of sites seem to have mixed individual 6S4A's in stock, but no matched quads. Hopefully replacing the power tube will get rid of that hum I am experiencing. Sahara, another site you can try contacting is http://www.audiotubes.com/bjtubes.htm . They seem to offer matching for a small additional price.

 

[shipsupt]

I always find it's best to contact them and ask.  I don't often find the on-line inventory all that accurate, and they often have sources to find tubes you are looking for.

 

[Golfnutz]

This site has 328 listed as available  http://www.surplussales.com/Tubes-Sock-Acc/TubeSpecials.html
 
I've never dealt with them, so I don't know what they're like. Just put 6S4A in the site search field. I also recommend calling them first to see if matched pairs/quads are available.

 

[Sahara]

Thank you very much for all the replies. I think with all the addresses and the possibility of matching tubes in audiotubes the problem is almost solved.

The problem that I had was pointed to by JDrive: There were quite a few 6S4A tubes but none of them matched quads...

Another question for those who have tried matched tubes by audiotubes.com 
 Do they do well the job? are tubes well matched?