[chrisdrop]

With an external heater supply, I run No. 27 triodes as drivers, manufactured in 1929.

Very cool. Love the look. After recent posts I had some 76 adapters / 76s on my list ... I guess the 56 and 27 are options if you externally heat them (<6,3v heater).

 

[attmci]

Pulled out my box of 6N7G tubes to check what I have. But first, these tubes come in three variants:
6N7 metal
6N7G shoulder type glass
6N7GT straight tubular glass
I have the following 6N7G tubes; mostly from the 40's: Arcturus, Sylvania, Ken-Rad and Mazda (Visseaux) - will have to revisit them. Also have the Mullard ECC31.
The Ken-Rad is a very pretty tube:

Mordy, Do you want to try this:

https://www.ebay.com/itm/6N7G-Vacuu...532481?hash=item44587f9581:g:0G0AAOSwkqBekLeT

 

[mordy]

Nice @mordy. Some 6N7* tubes have been "on my list" based on comments from this thread. I'll have to go back over the thread to see what combos people were running.

I have a lot of straight-glass and metal tubes. I wanted to add some pretty shoulder-types. I noticed on the radiomuseum link for the 6N7G, they list the GT as a successor tube. Is there some reason the straight-glass tubes were deemed "better" at the time? I can't really discern any "general properties" of shoulder-type vs straight-glass tubes, but if there are any consistent differences I'd be keen to hear/learn.

@leftside - I think yours can take 6N7* tubes in the 6J5* slots, is that right?

I was wondering what the oldest tubes I had were. I'll have to look. What are the oldest tubes that any of you are regularly using? I don't think I have any from the 30s... Now I have a mission. What are even the oldest feasible tubes for these amps? Things to ponder while listening ...

The 6J5 is a single triode and the 6N7 is a dual triode. Maybe you can make it work in the 6J5 socket with suitable adapters using two of the 6N7 tubes.
As a rule, the larger and older ST types often sound better than the GT (tubular glass) equivalents, but there are of course exceptions. Over the years the tubes became smaller and smaller. Before the transistor era sub miniature 6SN7 equivalents and others were developed with flying leads. Here is a picture where you can compare the size to a 6N6P 9pin tube:

And this is how one of them looks - comes as triodes, dual triodes and pentodes:

 

[mordy]

Mordy, Do you want to try this:

https://www.ebay.com/itm/6N7G-Vacuu...532481?hash=item44587f9581:g:0G0AAOSwkqBekLeT

Thanks - looks good and the price is good but already sold. On the other hand I have what I imagine are similar sounding tubes - Tung Sol 6F8G. These tubes are very pretty looking.

 

[mordy]

Glenn is tricky - it is hard to put tubes in the amp that don't sound pretty darn good. Here is a dual triode, making a rare appearance in my amp. This RCA 6N7G sounds pretty good out of the box and I do like the look of it. Below is also the 1st adapter I have gotten via xulingmrs. It came quickly from China in 1 week, which surprised me.

The date code is "S2". According to this, it seems plausible that it is March 1957 or 1942. I guess it is overly optimistic to expect it to be '42.

Happy listening all.

Hi Chrisdrop,
Put in a 1949 Sylvania 6N7G (branded GM DELCO) together with the TFK EL11 and Bendix 6080WB.
After warming up for a while it is a very pleasant sound with beautiful midrange.

As you said, most tubes sound good in the GOTL....
And for once the tubes match in height (more or less)...

 

[attmci]

Thanks - looks good and the price is good but already sold. On the other hand I have what I imagine are similar sounding tubes - Tung Sol 6F8G. These tubes are very pretty looking.

When I post, it's still available. Next time, I will PM you. LOL

 

[2359glenn]

The 6J5 is a single triode and the 6N7 is a dual triode. Maybe you can make it work in the 6J5 socket with suitable adapters using two of the 6N7 tubes.
As a rule, the larger and older ST types often sound better than the GT (tubular glass) equivalents, but there are of course exceptions. Over the years the tubes became smaller and smaller. Before the transistor era sub miniature 6SN7 equivalents and others were developed with flying leads. Here is a picture where you can compare the size to a 6N6P 9pin tube:

And this is how one of them looks - comes as triodes, dual triodes and pentodes:

You can try only using 1/2 the 6N7 or try tying both 1/2s in parallel and see if that works.
I am sure 1/2 will work fine.

 

[Zachik]

You can try only using 1/2 the 6N7 or try tying both 1/2s in parallel and see if that works.
I am sure 1/2 will work fine.

Glenn - if using 1/2, won't it cause the tube (over time) to be unbalanced (1 side stay new while the other side wear out)?

 

[2359glenn]

Yes it will over time.
You can have one adapter using the other 1/2 and switch every once in awhile.
The 6N7 is a output tube and using it in a 6J5 socket is barley using it at all so I don't think it will ever get week.
Plus nobody leaves the tubes in long enough to get one side week.

 

[L0rdGwyn]

The 6N7 and 6J5 have similar pinouts, but the dual sections of the 6N7 have the orientation of the plates and grids swapped from that of the 6J5. For compatibility of both tubes, the socket must be wired with the two 6N7 triodes in parallel.

6J5


6N7

 

[2359glenn]

Just put a jumper wire between the 2 grids and 1/2 would be working.

 

[hpamdr]

Just put a jumper wire between the 2 grids and 1/2 would be working.

In F.A. the drivers are 6SN7 where both triode are in parallel.
I have for my tube analyzer a strapped adapter i use to get amplification factor, Curves, .... in strapped parallel mode.
This is a sample adapter using socket (hole) and base (pin)
6N7 (G/GT) Socket to 6J5 base
1 -> 1
2 -> 2
3 -> 3
4 -> 5
5 -> 5
6 -> 3
7 -> 7
8 -> 8

If you want to use the tube only in the 6J5 socket, yoiu can also connect directly the pin 4-5 and 3-6 on the tube base welding enameled cable.

If you just plug, it will not work. You can connect pin 4/5 to only have Triode 1. If you only use this way you can unballance the tube stronger T2 after many many many hours of listening. (which should not occurs with usual tube rolling)

Another solution i've used in F.A is to build a 2 to 1 adapter like the 6SN7 socket in Gleen amp one triode by chanel..

1 socket 2 bases
So Left Right
1 -> 1 1
2 -> 2 -
3 -> 3 -
4 -> 5 -
5 -> - 5
6 -> - 3
7 -> 7 -
8 -> 8 8

In this case i prefer to only use one amplifier side to heat 6N7 as normally you should not have a loop in the heating circuit. The best is also to braid/twist connected wire 2 and 7 from base to socket...

 

[L0rdGwyn]

Have some very rare tubes on the way, I am excited about them, Klangfilm 70503, near-equivalent to the Telefunken REN904. They might not be pretty, but certain to be exquisite sonically, the seller sent me an offer I could not refuse for a NOS pair. These will be the rarest tubes I have in my collection from this family, followed by the gold Telefunken REN904. Can't wait to get them in my amp!

 

[mordy]

Are these tubes made by Telefunken? 30’s?

 

[L0rdGwyn]

Are these tubes made by Telefunken? 30’s?

Klangfilm was founded by Siemens and AEG - parent company of Telefunken - pre-WWII. In 1941 Siemens bought out AEG, so many post WWII Klangfilm products were labelled Siemens-Klangfilm. Likely in part of their scarcity, there are no available datasheets for this particular model, they are listed as a near-equivalent to the REN904 on Radiomuseum, leading me to believe they are not internally identical, but it is possible they are the same, perhaps my ears will tell me I'm sure our tube historian, Ken, could shed more light on the relationship between Klangfilm and AEG (read Telefunken). And yes, 1930s.